Write the big boi docs content tree
Replace the ancient `docs/index.rst` (still teaching `tractor.run()`, `@stream` + arbiters..) with a full ~32 page tree teaching ONLY the current api (`.wait_for_result()`, registrar naming, `@context` + `open_context()` as the core model), - landing: hero example, feature cards + canon links, - `start/`: install + a 4-example quickstart on-ramp, - `explain/`: an "SC across processes" essay distilling the essence per #157's orig ask + a runtime architecture tour, - `guide/`: 12 task-focused pages incl the flagship multi-process debugging walkthrough, `Context` + `MsgStream` deep-dives, cancellation semantics (self-vs-cross cancel rules), discovery, infected `asyncio`, typed msging + the #126 testing-tips page, - `api/`: 10 curated autodoc pages (all targets import-verified vs the reorg'd subpkg tree), - `project/`: changelog include, ported dev-tips (drops old `docs/dev_tips.rst`) + roadmap. Every code block is a `literalinclude` from `examples/` - zero duplication, all CI-run - w/ `d2` figs floated into the RHS margin per the 3-col design. Build is green; the 24 remaining warnings all source from lib docstring rst-isms or legacy `NEWS.rst` content. Substantially resolves #157 (refine round pending); chips at #175 + #126. Prompt-IO: ai/prompt-io/claude/20260611T175152Z_8526985c_prompt_io.md (this patch was generated in some part by [`claude-code`][claude-code-gh]) [claude-code-gh]: https://github.com/anthropics/claude-code
parent
9fa1d73418
commit
8567f1b3c1
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@ -0,0 +1,93 @@
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---
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||||
model: claude-fable-5[1m]
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service: claude
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session: 0780a862-e19a-4f0a-86cd-c8afc0997757
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timestamp: 2026-06-11T17:51:52Z
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git_ref: 8526985c
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scope: docs+code+config
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substantive: true
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raw_file: 20260611T175152Z_8526985c_prompt_io.raw.md
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---
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## Prompt
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> we need big boi docs; ours are way out of date and generally
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> terrible. i'd like to use a sphinx theme in the vein and/or
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> one-of/nearly-the-same-as used in one or all of the `msgspec`,
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> `numpy`, `ray`, `xonsh`, `polars` projects.
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>
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> see the following oustanding but now very old issues to guide
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> you: #175, #126, #123, #157
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>
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> we should try to target a 3 columned sphinx theme with,
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> - document index-nav on left,
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> - body content in middle,
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> - diagrams (ideally in d2lang if possible) on RHS
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>
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> optimize for (if possible),
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> - reusing examples code without duplication in docs,
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> - generating new examples from todos throughout code base,
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> - distilling the essence of SC across processes in the simplest
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> and most friendly way possible.
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>
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> do this work in a /open-wkt and do you best without my guidance
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> for the first major pass - we will refine asap once you are
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> complete.
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Session settings: `/effort max` + ultracode (multi-agent workflow
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orchestration). Fully autonomous first pass; two orchestrated
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agent fleets were used (6-agent recon survey, then 10-agent
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content fan-out: 9 section writers + 1 examples smith), with the
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orchestrator authoring the landing page, SC essay, sphinx
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scaffold, d2 pipeline + diagram sources, CI workflow and all
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integration/fix passes directly.
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## Response summary
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Complete sphinx docs revamp on branch `wkt/big_boi_docs`:
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`pydata-sphinx-theme` 0.18 (3-column: left nav / content /
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page-toc, with d2 diagrams + asides floated into the RHS margin
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via custom CSS), sphinx 9.1, a local `.. d2::` directive
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rendering `docs/diagrams/*.d2` sources with committed-SVG
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fallback, a vendored `.. margin::` directive, ~25 new doc pages
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(landing, start/, explain/, 12 guides, 10 api-ref pages,
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project/), 5 new auto-tested examples + 3 modernized + 1
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renamed, and a gh-pages deploy workflow (issue #123). All
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example code is `literalinclude`d from `examples/` (zero
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duplication, CI-verified). Build: green, 24 warnings all
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pre-existing-docstring/NEWS sourced.
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## Files changed
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See the branch diff (uncommitted at entry-write time):
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> `git diff test_cpu_throttling..wkt/big_boi_docs`
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> `git -C <wkt> status --short` (pre-commit working tree)
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- `docs/conf.py` — full rewrite for pydata theme + ext stack
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- `docs/_ext/d2diagrams.py` — new `.. d2::` sphinx directive
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- `docs/_ext/marginalia.py` — new `.. margin::` directive
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- `docs/_static/css/custom.css` — b&w skin + RHS margin floats
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- `docs/diagrams/*.d2` (7) — diagram sources (sketch/grayscale)
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- `docs/_diagrams/*.svg` (7) — committed rendered fallbacks
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- `docs/index.rst` — new landing (replaces dead-API doc)
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- `docs/start/*.rst` (3), `docs/explain/*.rst` (3),
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`docs/guide/*.rst` (13), `docs/api/*.rst` (10),
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`docs/project/*.rst` (3) — new content tree
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- `docs/dev_tips.rst` — removed (ported to project/dev-tips)
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- `examples/{typed_payloads,nested_actor_tree,
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service_daemon_discovery,uds_transport_actor_tree,
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streaming_broadcast_fanout}.py` — new, smoke-tested
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- `examples/{a_trynamic_first_scene,
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actor_spawning_and_causality,parallelism/single_func}.py` —
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`.result()` -> `.wait_for_result()` modernization
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- `examples/parallelism/concurrent_futures_primes.py` — renamed
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from leading-underscore + trio-runner shim added
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- `pyproject.toml` — `docs` dependency-group filled in
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- `uv.lock` — relock for docs group
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- `.github/workflows/docs.yml` — build + gh-pages deploy
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## Human edits
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None yet — entry written pre-commit; the author reviews, stages
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and commits manually (per repo workflow policy).
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@ -0,0 +1,49 @@
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---
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model: claude-fable-5[1m]
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service: claude
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timestamp: 2026-06-11T17:51:52Z
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git_ref: 8526985c
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diff_cmd: git diff test_cpu_throttling..wkt/big_boi_docs
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---
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# Raw output pointers (diff-ref mode)
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All generated content is code/config/docs committed alongside
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this entry on branch `wkt/big_boi_docs`; per the prompt-io
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diff-ref decision rule each file's verbatim content is the diff
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itself rather than a copy here:
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> `git diff test_cpu_throttling..wkt/big_boi_docs -- docs/`
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> `git diff test_cpu_throttling..wkt/big_boi_docs -- examples/`
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> `git diff test_cpu_throttling..wkt/big_boi_docs -- pyproject.toml uv.lock .github/`
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## Generation notes (non-code output summary)
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- Theme research (web, agent-verified 2026-06-11): msgspec=furo,
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xonsh=furo, numpy/ray/polars=pydata-sphinx-theme (ray migrated
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off sphinx-book-theme); sphinx-book-theme 1.2.0 hard-pins
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pydata 0.16.1 (stale) -> chose pydata 0.18 + sphinx 9.1.
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- d2 ecosystem: no production-grade pypi extension exists
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(sphinxcontrib-d2lang 0.0.5 ignores returncodes, uuid4 output
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names; sphinx-d2 is an empty stub) -> wrote local
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`docs/_ext/d2diagrams.py` (~230 LOC) with D2_BIN env
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discovery, mtime caching, committed-SVG fallback and
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literal-block last resort.
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- Diagrams authored in d2 (theme-id 1 "Neutral Grey" + sketch
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mode + ELK layout, validated by render + headless-firefox
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screenshot loop): actor_tree, context_handshake (real
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msg-spec names Start/StartAck/Started/Yield/Stop/Return),
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streaming_pipeline, runtime_stack, debug_lock,
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error_propagation, infected_aio.
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- API truth enforced from a 6-agent recon pass over the
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reorganized package tree (runtime/, discovery/, spawn/, ipc/,
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msg/, devx/, trionics/): docs teach `.wait_for_result()`,
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registrar (not arbiter) naming, `@tractor.context` +
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`open_context()` as the core model, `run_in_actor()` as
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convenience only.
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- All ~30 literalincluded example scripts verified present; 9
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touched/new example files smoke-run green (exit 0, <16s).
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- Final build: `sphinx-build -b html` succeeded; 24 residual
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warnings, every one sourced from pre-existing library
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docstring rst-isms or legacy NEWS.rst content (left untouched
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by design; flagged for a follow-up docstring lint pass).
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@ -0,0 +1,134 @@
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Contexts and streaming
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======================
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The modern core of ``tractor``: a :class:`Context` links a task in
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one actor to a task in another as a *single* structured concurrency
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(SC) scope stretched across the IPC boundary — errors, results and
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cancellation flow between the pair `exactly like trio`_ tasks under
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a common `nursery`_. Open one with ``Portal.open_context()`` (see
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:func:`tractor._context.open_context_from_portal` in
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:doc:`/api/core`), then optionally bridge a bidirectional
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:class:`MsgStream` between the two tasks.
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.. d2:: diagrams/context_handshake.d2
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:caption: The ``open_context()`` <-> ``ctx.started()`` handshake.
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:margin:
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:alt: parent and child actor context handshake sequence
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For the guided, example-driven tour see :doc:`/guide/context`; this
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page is the precise API surface.
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.. currentmodule:: tractor
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The ``@context`` decorator
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--------------------------
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.. autofunction:: context
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.. note::
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The decorated function **must** declare a parameter annotated
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``tractor.Context`` (any param name works); the runtime injects
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the context instance there on each remote invocation. Pass
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``pld_spec`` to type-restrict (and validate) the payloads this
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endpoint may shuttle — violations raise
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:class:`MsgTypeError`. See ``examples/typed_payloads.py``.
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``Context``
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-----------
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.. autoclass:: Context
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:members: started,
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wait_for_result,
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cancel,
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cid,
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chan,
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side,
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cancel_called,
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cancelled_caught,
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cancel_acked,
|
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canceller,
|
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maybe_error,
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outcome
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.. deprecated:: 0.1.0a6
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|
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``Context.result()`` warns; use :meth:`Context.wait_for_result`.
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|
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.. note::
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|
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A :class:`Context` is **not** a :class:`trio.CancelScope`:
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:meth:`Context.cancel` requests cancellation of the *remote*
|
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peer task and does not cancel the local scope. If *you*
|
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requested the cancel, the resulting :class:`ContextCancelled`
|
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is absorbed at ``open_context()`` exit; a cancel originating
|
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anywhere else (the peer, or a third-party actor recorded in
|
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:attr:`ContextCancelled.canceller`) *is* raised locally. This
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self-vs-cross-cancel rule is the key to writing correct
|
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inter-actor teardown logic — see :doc:`/guide/context`.
|
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|
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Bidirectional streaming
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-----------------------
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|
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.. autofunction:: tractor._streaming.open_stream_from_ctx
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.. note::
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|
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:func:`~tractor._streaming.open_stream_from_ctx` is bound as
|
||||
the **method-alias** ``Context.open_stream()`` — call it as
|
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``async with ctx.open_stream() as stream:``. Both sides of the
|
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context must enter it for the dialog to be open.
|
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|
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.. autoclass:: MsgStream
|
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:members: send,
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receive,
|
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receive_nowait,
|
||||
aclose,
|
||||
subscribe,
|
||||
ctx,
|
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closed
|
||||
|
||||
.. note::
|
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|
||||
A :class:`MsgStream` is one-shot use: once closed it can never
|
||||
be "re-opened" — open a fresh :class:`Context` instead. Remote
|
||||
end-of-stream surfaces as :class:`StopAsyncIteration` from
|
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``async for``; un-consumed sends overrun the receiver and raise
|
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:class:`tractor._exceptions.StreamOverrun` unless the context
|
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was opened with ``allow_overruns=True``.
|
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|
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:meth:`MsgStream.subscribe` fans a single IPC stream out to
|
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multiple *local* tasks via a
|
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:class:`tractor.trionics.BroadcastReceiver` (see
|
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:doc:`/api/trionics`); the underlying allocation is idempotent and
|
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non-reversible for the stream's lifetime. See
|
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``examples/streaming_broadcast_fanout.py`` for the pattern in
|
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action.
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|
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Legacy one-way streaming
|
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------------------------
|
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|
||||
.. autofunction:: stream
|
||||
|
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.. warning::
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|
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``@tractor.stream`` and ``Portal.open_stream_from()`` are the
|
||||
*legacy* one-way streaming API kept for backward compat: a
|
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plain async-generator function streamed parent-ward with no
|
||||
child-side receive leg. New code should use
|
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``@tractor.context`` + ``ctx.open_stream()`` (bidirectional,
|
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SC-linked, typed). Note ``ctx`` is now a reserved param name
|
||||
for ``@context`` endpoints — ``@stream`` functions must use
|
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``stream`` instead, and ``ctx.send_yield()`` is deprecated in
|
||||
favor of :meth:`MsgStream.send`.
|
||||
|
||||
.. seealso::
|
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|
||||
:doc:`/api/errors` for :class:`ContextCancelled` /
|
||||
:class:`MsgTypeError` semantics, :doc:`/api/msg` for payload
|
||||
typing via ``pld_spec`` and codecs, :doc:`/api/trionics` for
|
||||
the broadcast fan-out machinery, and the guided tours in
|
||||
:doc:`/guide/streaming` + :doc:`/guide/cancellation`.
|
||||
|
||||
.. _exactly like trio: https://trio.readthedocs.io/en/latest/reference-core.html#cancellation-semantics
|
||||
.. _nursery: https://trio.readthedocs.io/en/latest/reference-core.html#nurseries-and-spawning
|
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|
|
@ -0,0 +1,157 @@
|
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Runtime and spawning
|
||||
====================
|
||||
|
||||
The core lifecycle API: boot the runtime in your root process,
|
||||
spawn trio-"actors" (processes running ``trio.run()`` task trees)
|
||||
under a one-cancels-all supervisor, and talk to them through
|
||||
portals. This is structured concurrency (SC) applied *transitively*:
|
||||
every spawned process is owned by a nursery block and errors
|
||||
`always propagate`_. If you can create zombies it **is a bug**.
|
||||
|
||||
.. currentmodule:: tractor
|
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|
||||
Booting the runtime
|
||||
-------------------
|
||||
|
||||
.. autofunction:: open_root_actor
|
||||
|
||||
.. note::
|
||||
|
||||
The env vars ``TRACTOR_LOGLEVEL`` and ``TRACTOR_SPAWN_METHOD``
|
||||
override the ``loglevel`` / ``start_method`` params so you can
|
||||
crank verbosity or swap spawn backends without touching app
|
||||
code. Exactly **one** IPC transport may be enabled per actor
|
||||
(see ``enable_transports`` and :doc:`/api/ipc`).
|
||||
|
||||
.. autofunction:: run_daemon
|
||||
|
||||
Spawning actors
|
||||
---------------
|
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|
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.. d2:: diagrams/actor_tree.d2
|
||||
:caption: A supervised actor (process) tree.
|
||||
:margin:
|
||||
:alt: root actor supervising a tree of subactors
|
||||
|
||||
.. autofunction:: open_nursery
|
||||
|
||||
.. autoclass:: ActorNursery
|
||||
:members: start_actor,
|
||||
run_in_actor,
|
||||
cancel,
|
||||
cancel_called,
|
||||
cancelled_caught
|
||||
|
||||
.. note::
|
||||
|
||||
:meth:`ActorNursery.start_actor` (daemon actor + portal) is the
|
||||
blessed spawning primitive; pair it with
|
||||
``Portal.open_context()`` for SC-linked remote tasks.
|
||||
:meth:`ActorNursery.run_in_actor` is a *convenience* one-shot —
|
||||
spawn, run a single task, auto-cancel after the result — slated
|
||||
to be rebuilt as a high-level wrapper, so don't design around
|
||||
it as the core model.
|
||||
|
||||
.. deprecated:: 0.1.0a6
|
||||
|
||||
``ActorNursery.cancelled`` warns; use
|
||||
:attr:`ActorNursery.cancel_called` and
|
||||
:attr:`ActorNursery.cancelled_caught`. The ``rpc_module_paths``
|
||||
kwarg is likewise deprecated in favor of ``enable_modules``.
|
||||
|
||||
Portals
|
||||
-------
|
||||
|
||||
A :class:`Portal` "opens a portal" into a peer actor's memory
|
||||
domain: you call functions and start SC-linked tasks *over IPC* as
|
||||
though they were local, with results, errors and cancellation
|
||||
flowing back `exactly like trio`_.
|
||||
|
||||
.. autoclass:: Portal
|
||||
:members: run,
|
||||
run_from_ns,
|
||||
open_stream_from,
|
||||
wait_for_result,
|
||||
cancel_actor,
|
||||
chan
|
||||
|
||||
.. deprecated:: 0.1.0a6
|
||||
|
||||
``Portal.result()`` warns; use :meth:`Portal.wait_for_result`.
|
||||
The str-form ``Portal.run('mod.path', 'fn_name')`` also warns;
|
||||
pass a function *object* whose module is listed in the target's
|
||||
``enable_modules``. ``Portal.channel`` is the legacy spelling
|
||||
of :attr:`Portal.chan`.
|
||||
|
||||
.. autofunction:: tractor._context.open_context_from_portal
|
||||
|
||||
.. note::
|
||||
|
||||
:func:`~tractor._context.open_context_from_portal` is bound as
|
||||
the **method-alias** ``Portal.open_context()`` — that's the
|
||||
spelling you should actually call:
|
||||
``portal.open_context(fn, **kwargs)``. See :doc:`/api/context`
|
||||
for the full ``Context`` + ``MsgStream`` API it unlocks.
|
||||
|
||||
.. note::
|
||||
|
||||
:meth:`Portal.cancel_actor` cancels the *whole* remote runtime
|
||||
and process (machine-level), not a single task — use
|
||||
:meth:`Context.cancel` for task-level cancellation. Pass
|
||||
``raise_on_timeout=True`` to get an ``ActorTooSlowError`` you
|
||||
can escalate per SC discipline (see :doc:`/api/errors`).
|
||||
|
||||
Clusters
|
||||
--------
|
||||
|
||||
.. autofunction:: open_actor_cluster
|
||||
|
||||
Spawn a *flat* cluster of ``count`` worker actors (default: one
|
||||
per core) all serving the RPC ``modules`` list, yielding a
|
||||
``dict[str, Portal]`` keyed by actor name. Handy for
|
||||
embarrassingly parallel fan-out; see ``examples/quick_cluster.py``.
|
||||
|
||||
Runtime introspection
|
||||
---------------------
|
||||
|
||||
.. autofunction:: current_actor
|
||||
|
||||
.. autoclass:: Actor
|
||||
:members: aid,
|
||||
name,
|
||||
uid,
|
||||
is_registrar,
|
||||
is_infected_aio,
|
||||
cancel_soon
|
||||
|
||||
.. note::
|
||||
|
||||
:class:`Actor` is the per-process runtime singleton (msg loop,
|
||||
RPC scheduling, IPC server) — you never instantiate it yourself
|
||||
and should normally only touch the identity/introspection
|
||||
surface listed above. The canonical identity type is
|
||||
:attr:`Actor.aid` (a ``tractor.msg.Aid`` struct);
|
||||
:attr:`Actor.uid` is the legacy ``(name, uuid)`` 2-tuple which
|
||||
is still pervasive in logs and error metadata.
|
||||
|
||||
.. deprecated:: 0.1.0a6
|
||||
|
||||
``Actor.is_arbiter`` warns; use :attr:`Actor.is_registrar`.
|
||||
The ``arbiter_addr`` constructor kwarg is deprecated for
|
||||
``registry_addrs``.
|
||||
|
||||
.. autofunction:: current_ipc_ctx
|
||||
|
||||
.. autofunction:: is_root_process
|
||||
|
||||
.. autofunction:: get_runtime_vars
|
||||
|
||||
.. seealso::
|
||||
|
||||
:doc:`/api/context` for the SC-linked remote task API,
|
||||
:doc:`/api/discovery` for finding actors by name, and the
|
||||
guided tours in :doc:`/guide/spawning`, :doc:`/guide/rpc` and
|
||||
:doc:`/guide/context`.
|
||||
|
||||
.. _always propagate: https://trio.readthedocs.io/en/latest/design.html#exceptions-always-propagate
|
||||
.. _exactly like trio: https://trio.readthedocs.io/en/latest/reference-core.html#cancellation-semantics
|
||||
|
|
@ -0,0 +1,92 @@
|
|||
Debugging and devx: ``tractor.devx``
|
||||
====================================
|
||||
|
||||
Multi-process debugging that actually works: boot the tree with
|
||||
``open_root_actor(debug_mode=True)`` (or pass it to
|
||||
``open_nursery()``) and any crash or explicit pause in *any* actor
|
||||
acquires a tree-global TTY lock and drops you into a
|
||||
`pdbp`_-powered REPL — one actor at a time, ``SIGINT`` shielded,
|
||||
no garbled terminals. The top-level helpers below are the daily
|
||||
drivers; the rest of the toolbox lives under ``tractor.devx``.
|
||||
|
||||
.. currentmodule:: tractor
|
||||
|
||||
Pausing and post-mortems
|
||||
------------------------
|
||||
|
||||
.. autofunction:: pause
|
||||
|
||||
.. autofunction:: pause_from_sync
|
||||
|
||||
.. note::
|
||||
|
||||
:func:`pause_from_sync` needs the `greenback`_ portal: boot
|
||||
with ``open_root_actor(maybe_enable_greenback=True)`` (mind
|
||||
the `performance implications`_). With ``debug_mode`` on, the
|
||||
built-in ``breakpoint()`` is also remapped to a
|
||||
``tractor``-safe equivalent.
|
||||
|
||||
.. autofunction:: post_mortem
|
||||
|
||||
.. deprecated:: 0.1.0a6
|
||||
|
||||
``tractor.breakpoint()`` warns and simply calls :func:`pause`
|
||||
— use :func:`tractor.pause` (async) or
|
||||
:func:`tractor.pause_from_sync` in new code.
|
||||
|
||||
Crash handling for CLIs and sync entrypoints
|
||||
--------------------------------------------
|
||||
|
||||
.. currentmodule:: tractor.devx
|
||||
|
||||
.. autofunction:: open_crash_handler
|
||||
|
||||
.. autofunction:: maybe_open_crash_handler
|
||||
|
||||
.. note::
|
||||
|
||||
Both are *sync* context managers usable before (or without)
|
||||
``trio.run()`` — wrap your CLI ``main()`` to get a post-mortem
|
||||
REPL on any uncaught exception instead of a bare traceback.
|
||||
|
||||
Runtime hang-hunting
|
||||
--------------------
|
||||
|
||||
.. autofunction:: enable_stack_on_sig
|
||||
|
||||
With stackscope_ integration enabled (also via
|
||||
``open_root_actor(enable_stack_on_sig=True)`` or the
|
||||
``TRACTOR_ENABLE_STACKSCOPE`` env var) a ``SIGUSR1`` triggers a
|
||||
full trio task-tree dump from every actor — works on live,
|
||||
*non*-debug-mode trees too:
|
||||
|
||||
.. code:: sh
|
||||
|
||||
pkill --signal SIGUSR1 -f <part-of-your-cmd>
|
||||
|
||||
Dumps also tee to ``/tmp/tractor-stackscope-<pid>.log`` so you
|
||||
still get output under captured/CI stdio.
|
||||
|
||||
Lower-level debug plumbing
|
||||
--------------------------
|
||||
|
||||
.. autofunction:: mk_pdb
|
||||
|
||||
.. autofunction:: maybe_wait_for_debugger
|
||||
|
||||
:func:`maybe_wait_for_debugger` is mainly useful in runtime/test
|
||||
code that must avoid tearing down a tree while a child still
|
||||
holds the global debug lock.
|
||||
|
||||
.. seealso::
|
||||
|
||||
:doc:`/api/errors` for the boxed error types you'll inspect
|
||||
from the REPL, :doc:`/api/core` for the ``debug_mode`` /
|
||||
``maybe_enable_greenback`` / ``enable_stack_on_sig`` boot
|
||||
flags on :func:`tractor.open_root_actor`, and
|
||||
:doc:`/guide/debugging` for the guided multi-actor REPL tour.
|
||||
|
||||
.. _pdbp: https://github.com/mdmintz/pdbp
|
||||
.. _greenback: https://greenback.readthedocs.io/en/latest/
|
||||
.. _performance implications: https://greenback.readthedocs.io/en/latest/principle.html#performance
|
||||
.. _stackscope: https://github.com/oremanj/stackscope
|
||||
|
|
@ -0,0 +1,67 @@
|
|||
Discovery and the registrar
|
||||
===========================
|
||||
|
||||
Every actor registers its ``(name, uuid)`` and transport addresses
|
||||
with a *registrar* actor — by default the root of the tree, or
|
||||
whichever actor serves at the ``registry_addrs`` you boot with.
|
||||
The discovery API lets any actor look up any other **by name** and
|
||||
get back a connected :class:`~tractor.Portal`, giving you
|
||||
service-discovery patterns (daemons, service trees, multi-host
|
||||
meshes) without hard-coding addresses.
|
||||
|
||||
Lookups first scan already-connected peers before RPC-ing the
|
||||
registrar, and multihomed results are ranked UDS > local TCP >
|
||||
remote TCP. See ``examples/service_daemon_discovery.py`` for the
|
||||
canonical daemon + lookup pattern.
|
||||
|
||||
.. currentmodule:: tractor
|
||||
|
||||
Lookup APIs
|
||||
-----------
|
||||
|
||||
.. autofunction:: find_actor
|
||||
|
||||
.. autofunction:: wait_for_actor
|
||||
|
||||
.. autofunction:: query_actor
|
||||
|
||||
.. autofunction:: get_registry
|
||||
|
||||
.. note::
|
||||
|
||||
:func:`find_actor` yields ``None`` when nothing is registered
|
||||
under the name (or raises with ``raise_on_none=True``);
|
||||
:func:`wait_for_actor` blocks until the name appears;
|
||||
:func:`query_actor` only *looks up* the address without
|
||||
connecting to the target.
|
||||
|
||||
The ``Registrar``
|
||||
-----------------
|
||||
|
||||
.. autoclass:: Registrar
|
||||
:show-inheritance:
|
||||
|
||||
A :class:`Registrar` is just an :class:`~tractor.Actor` subtype
|
||||
maintaining the name -> addresses table; you rarely touch it
|
||||
directly beyond passing ``registry_addrs`` /
|
||||
``ensure_registry=True`` to :func:`~tractor.open_root_actor`.
|
||||
Check :attr:`Actor.is_registrar <tractor.Actor.is_registrar>` to
|
||||
ask "am I it?".
|
||||
|
||||
Legacy ``Arbiter`` alias
|
||||
------------------------
|
||||
|
||||
.. deprecated:: 0.1.0a6
|
||||
|
||||
``tractor.Arbiter`` survives only as a class alias of
|
||||
:class:`Registrar` and all "arbiter" terminology is replaced
|
||||
by "registrar"/"registry" across the API: ``get_arbiter()`` is
|
||||
removed (use :func:`get_registry`) and the ``arbiter_addr``
|
||||
kwarg is replaced by ``registry_addrs``.
|
||||
|
||||
.. seealso::
|
||||
|
||||
:doc:`/api/core` for booting a registrar via
|
||||
``open_root_actor(registry_addrs=...)``, :doc:`/api/ipc` for
|
||||
the transport/address model the registry stores, and
|
||||
:doc:`/guide/discovery` for the worked walkthrough.
|
||||
|
|
@ -0,0 +1,102 @@
|
|||
Errors and cancellation types
|
||||
=============================
|
||||
|
||||
``tractor`` extends trio's "exceptions `always propagate`_" rule
|
||||
across the process boundary: a crash in any actor is serialized as
|
||||
an ``Error`` msg, shuttled over IPC, and re-raised in the linked
|
||||
parent scope as a *boxed* :class:`RemoteActorError` — preserving
|
||||
the original type, traceback text and source-actor identity, even
|
||||
across multi-hop relays (a.k.a. "inceptions").
|
||||
|
||||
The most-used types below are importable from ``tractor``
|
||||
directly; the remainder live in ``tractor._exceptions`` (not yet
|
||||
re-exported at top level).
|
||||
|
||||
.. currentmodule:: tractor
|
||||
|
||||
Boxed remote errors
|
||||
-------------------
|
||||
|
||||
.. autoexception:: RemoteActorError
|
||||
:members: boxed_type,
|
||||
src_uid,
|
||||
relay_uid,
|
||||
pformat
|
||||
|
||||
.. code:: python
|
||||
|
||||
try:
|
||||
async with portal.open_context(ep_fn) as (ctx, first):
|
||||
...
|
||||
except tractor.RemoteActorError as rae:
|
||||
if rae.boxed_type is ValueError:
|
||||
... # remote task raised a `ValueError`
|
||||
|
||||
.. autoexception:: ContextCancelled
|
||||
:show-inheritance:
|
||||
:members: canceller
|
||||
|
||||
.. note::
|
||||
|
||||
Inspect :attr:`ContextCancelled.canceller` (the requesting
|
||||
actor's uid) to distinguish a *self*-requested cancel (absorbed
|
||||
at ``open_context()`` exit) from a *cross*-actor cancel (raised
|
||||
locally) — the full rules live in :doc:`/api/context`.
|
||||
|
||||
Typed-messaging errors
|
||||
----------------------
|
||||
|
||||
.. autoexception:: MsgTypeError
|
||||
:show-inheritance:
|
||||
:members: bad_msg,
|
||||
expected_msg_type
|
||||
|
||||
An "IPC ``TypeError``": a message failed validation against the
|
||||
active msg-spec / ``pld_spec`` (see :doc:`/api/msg`). Raised
|
||||
sender-side for control msgs (``Started``/``Return``) and
|
||||
receiver-side for stream ``Yield`` payloads.
|
||||
|
||||
.. autoexception:: tractor._exceptions.StreamOverrun
|
||||
:show-inheritance:
|
||||
|
||||
The sender out-paced the receiver's buffer on a
|
||||
:class:`~tractor.MsgStream` opened without
|
||||
``allow_overruns=True``; subtypes :class:`trio.TooSlowError`.
|
||||
|
||||
Transport and runtime errors
|
||||
----------------------------
|
||||
|
||||
.. autoexception:: TransportClosed
|
||||
|
||||
.. autoexception:: ModuleNotExposed
|
||||
:show-inheritance:
|
||||
|
||||
Raised when an RPC requests a function from a module not listed
|
||||
in the target actor's ``enable_modules`` allowlist —
|
||||
capability-style access control, not an import bug on your end ;)
|
||||
|
||||
.. autoexception:: tractor._exceptions.NoRuntime
|
||||
:show-inheritance:
|
||||
|
||||
Raised by :func:`tractor.current_actor` (and friends) when no
|
||||
actor runtime is up in the current process.
|
||||
|
||||
.. autoexception:: tractor._exceptions.ActorTooSlowError
|
||||
:show-inheritance:
|
||||
|
||||
A peer actor failed to ack a cancel request within the bounded
|
||||
wait — the SC-sanctioned escalation signal from APIs like
|
||||
``Portal.cancel_actor(raise_on_timeout=True)``. Catch it to
|
||||
escalate (e.g. hard-kill via the supervising
|
||||
:class:`~tractor.ActorNursery`); never just ignore it, that's how
|
||||
zombies happen.
|
||||
|
||||
.. seealso::
|
||||
|
||||
:doc:`/api/context` for how cancellation and errors flow
|
||||
through a :class:`~tractor.Context`, :doc:`/api/devx` for
|
||||
crash-handling REPL tooling (``debug_mode``, post-mortems),
|
||||
and :doc:`/guide/cancellation` for the full SC-cancellation
|
||||
story.
|
||||
|
||||
.. _always propagate: https://trio.readthedocs.io/en/latest/design.html#exceptions-always-propagate
|
||||
|
|
@ -0,0 +1,67 @@
|
|||
API reference
|
||||
=============
|
||||
|
||||
This is the curated reference for ``tractor``'s public surface: the
|
||||
names you can import and lean on without reading runtime internals.
|
||||
Everything below is re-exported at the top level (``import
|
||||
tractor``) unless a page says otherwise; subsystems like
|
||||
``tractor.msg``, ``tractor.trionics``, ``tractor.to_asyncio``,
|
||||
``tractor.devx`` and ``tractor.log`` are importable as submodules.
|
||||
|
||||
``tractor`` is "just trio_" extended across processes: every API
|
||||
here is designed to keep the structured concurrency (SC) rules you
|
||||
already know from the `trio docs`_ intact across the process
|
||||
boundary. If a name isn't documented here it's an internal — expect
|
||||
it to change without notice B).
|
||||
|
||||
.. currentmodule:: tractor
|
||||
|
||||
Most-used names at a glance:
|
||||
|
||||
.. autosummary::
|
||||
:nosignatures:
|
||||
|
||||
open_root_actor
|
||||
open_nursery
|
||||
run_daemon
|
||||
ActorNursery
|
||||
Portal
|
||||
context
|
||||
Context
|
||||
MsgStream
|
||||
open_actor_cluster
|
||||
find_actor
|
||||
wait_for_actor
|
||||
get_registry
|
||||
current_actor
|
||||
current_ipc_ctx
|
||||
is_root_process
|
||||
get_runtime_vars
|
||||
RemoteActorError
|
||||
ContextCancelled
|
||||
MsgTypeError
|
||||
pause
|
||||
post_mortem
|
||||
Channel
|
||||
|
||||
.. toctree::
|
||||
:maxdepth: 1
|
||||
:caption: Reference pages
|
||||
|
||||
core
|
||||
context
|
||||
discovery
|
||||
errors
|
||||
msg
|
||||
trionics
|
||||
to_asyncio
|
||||
devx
|
||||
ipc
|
||||
|
||||
Where to next? If you're new, start with the runtime and spawning
|
||||
APIs in :doc:`/api/core`, then graduate to the inter-actor task
|
||||
linking model in :doc:`/api/context` — it's the heart of the whole
|
||||
system.
|
||||
|
||||
.. _trio: https://github.com/python-trio/trio
|
||||
.. _trio docs: https://trio.readthedocs.io/en/latest/
|
||||
|
|
@ -0,0 +1,89 @@
|
|||
IPC and logging
|
||||
===============
|
||||
|
||||
Under every portal, context and stream sits a per-peer
|
||||
:class:`~tractor.Channel`: a msgpack-typed messaging link wrapping
|
||||
one OS transport connection. Transports are pluggable per actor
|
||||
via ``enable_transports=['tcp' | 'uds']`` — TCP is the default,
|
||||
UDS (unix domain sockets) gives you port-less, same-host IPC with
|
||||
kernel-provided peer credentials for free — and exactly **one**
|
||||
transport may currently be enabled per actor.
|
||||
|
||||
.. d2:: diagrams/runtime_stack.d2
|
||||
:caption: Where ``Channel`` sits in the runtime stack.
|
||||
:margin:
|
||||
:alt: layered runtime stack from app code down to transports
|
||||
|
||||
Addresses are "unwrapped" tuples at the API edges:
|
||||
``('host', port)`` for TCP, filesystem-path pairs for UDS. For
|
||||
the full layering story — transport protocols, the IPC server,
|
||||
address types and the msg loop — see
|
||||
:doc:`/explain/architecture`.
|
||||
|
||||
.. currentmodule:: tractor
|
||||
|
||||
``Channel``
|
||||
-----------
|
||||
|
||||
.. autoclass:: Channel
|
||||
:members: from_addr,
|
||||
send,
|
||||
recv,
|
||||
aclose,
|
||||
connected,
|
||||
apply_codec,
|
||||
aid,
|
||||
laddr,
|
||||
raddr,
|
||||
closed
|
||||
|
||||
.. deprecated:: 0.1.0a6
|
||||
|
||||
``Channel.uid`` warns; use :attr:`Channel.aid` which carries
|
||||
richer (optional) identity fields beyond the legacy
|
||||
``(name, uuid)`` pair.
|
||||
|
||||
.. note::
|
||||
|
||||
You rarely construct a :class:`Channel` yourself — the runtime
|
||||
hands them out via :attr:`Portal.chan <tractor.Portal.chan>`
|
||||
and :attr:`Context.chan <tractor.Context.chan>`. Treat the
|
||||
send/recv surface as advanced API: normal apps should speak
|
||||
:class:`~tractor.MsgStream` instead.
|
||||
|
||||
Choosing a transport
|
||||
--------------------
|
||||
|
||||
.. literalinclude:: ../../examples/uds_transport_actor_tree.py
|
||||
:caption: examples/uds_transport_actor_tree.py
|
||||
:language: python
|
||||
|
||||
Logging
|
||||
-------
|
||||
|
||||
``tractor.log`` provides the structured, colorized console
|
||||
logging used across the runtime — with actor-name + task-aware
|
||||
record headers and extra log levels below :data:`logging.DEBUG`
|
||||
(``'transport'``, ``'runtime'``, ``'cancel'``, ``'devx'``) for
|
||||
spelunking the runtime itself. Use it for your app too: it's
|
||||
already distributed-system aware.
|
||||
|
||||
.. currentmodule:: tractor.log
|
||||
|
||||
.. autofunction:: get_logger
|
||||
|
||||
.. autofunction:: get_console_log
|
||||
|
||||
.. note::
|
||||
|
||||
The ``TRACTOR_LOGLEVEL`` env var overrides any caller-passed
|
||||
``loglevel`` (e.g. to ``open_root_actor()``) so you can crank
|
||||
console verbosity without touching code; subactors inherit
|
||||
the root's level by default.
|
||||
|
||||
.. seealso::
|
||||
|
||||
:doc:`/explain/architecture` for the transport/server
|
||||
internals, :doc:`/api/discovery` for how channel addresses
|
||||
get registered and found, and :doc:`/api/msg` for the codec
|
||||
layer every channel speaks.
|
||||
|
|
@ -0,0 +1,107 @@
|
|||
Typed messaging: ``tractor.msg``
|
||||
================================
|
||||
|
||||
All inter-actor communication rides a small, strictly-typed
|
||||
msgpack wire protocol built from :class:`msgspec.Struct` types —
|
||||
the "SC-shuttle" protocol that powers contexts, streams, RPC and
|
||||
cancellation. You normally never touch these msg types directly
|
||||
(the :class:`~tractor.Context` API speaks them for you) but you
|
||||
*do* use this subpackage to define **payload type contracts**: per
|
||||
endpoint via ``@tractor.context(pld_spec=...)`` or per channel via
|
||||
custom codecs.
|
||||
|
||||
Violations of an active msg-spec surface as
|
||||
:class:`~tractor.MsgTypeError` (see :doc:`/api/errors`); the full
|
||||
typed-payload workflow is shown in ``examples/typed_payloads.py``.
|
||||
|
||||
.. currentmodule:: tractor.msg
|
||||
|
||||
The protocol message set
|
||||
------------------------
|
||||
|
||||
.. autosummary::
|
||||
:nosignatures:
|
||||
|
||||
PayloadMsg
|
||||
Aid
|
||||
SpawnSpec
|
||||
Start
|
||||
StartAck
|
||||
Started
|
||||
Yield
|
||||
Stop
|
||||
Return
|
||||
CancelAck
|
||||
Error
|
||||
|
||||
``Aid`` (identity handshake) and ``SpawnSpec`` (parent -> child
|
||||
init) run at connection setup; ``Start``/``StartAck`` initiate an
|
||||
RPC task; ``Started``/``Yield``/``Stop``/``Return`` are the
|
||||
:class:`~tractor.Context` dialog phases; ``CancelAck`` and
|
||||
``Error`` close the loop on cancellation and (boxed) failure.
|
||||
``Msg`` is a legacy alias of ``PayloadMsg``. The union of all of
|
||||
the above is exported as ``MsgType`` (also ``__msg_spec__``).
|
||||
|
||||
.. automodule:: tractor.msg.types
|
||||
:no-members:
|
||||
|
||||
.. currentmodule:: tractor.msg
|
||||
|
||||
Codec construction and override
|
||||
-------------------------------
|
||||
|
||||
.. autofunction:: mk_codec
|
||||
|
||||
.. autoclass:: MsgCodec
|
||||
:members: encode,
|
||||
decode,
|
||||
msg_spec
|
||||
|
||||
.. autofunction:: mk_dec
|
||||
|
||||
.. autoclass:: MsgDec
|
||||
:members: decode,
|
||||
spec
|
||||
|
||||
.. autofunction:: apply_codec
|
||||
|
||||
.. autofunction:: current_codec
|
||||
|
||||
.. note::
|
||||
|
||||
:func:`apply_codec` swaps the codec via a
|
||||
:class:`contextvars.ContextVar` — the override only applies to
|
||||
the *current task* (and tasks it starts), not sibling tasks
|
||||
already running in the actor. Payload-decoding is layered: the
|
||||
outer codec leaves ``.pld`` fields as ``msgspec.Raw`` and each
|
||||
context's payload-receiver decodes them against *its* spec
|
||||
(the "cheap-or-nasty" validation pattern).
|
||||
|
||||
Namespace pointers
|
||||
------------------
|
||||
|
||||
.. autoclass:: NamespacePath
|
||||
:members: from_ref,
|
||||
load_ref,
|
||||
to_tuple
|
||||
|
||||
The ``'module.path:obj_name'`` :class:`str`-subtype used to
|
||||
address every RPC target function over the wire (same format as
|
||||
:func:`pkgutil.resolve_name`).
|
||||
|
||||
Pretty structs
|
||||
--------------
|
||||
|
||||
.. autoclass:: Struct
|
||||
:show-inheritance:
|
||||
|
||||
A :class:`msgspec.Struct` subtype with a multi-line pretty
|
||||
``__repr__`` — handy as a base for your own IPC payload types so
|
||||
crash logs stay readable.
|
||||
|
||||
.. seealso::
|
||||
|
||||
:doc:`/api/context` for where ``pld_spec`` typing plugs into
|
||||
the ``@context`` decorator, :doc:`/api/errors` for
|
||||
:class:`~tractor.MsgTypeError` semantics, and
|
||||
:doc:`/guide/msging` for the guided typed-messaging tour.
|
||||
|
|
@ -0,0 +1,97 @@
|
|||
asyncio interop: ``tractor.to_asyncio``
|
||||
=======================================
|
||||
|
||||
"Infected asyncio" mode: spawn an actor with
|
||||
``start_actor(..., infect_asyncio=True)`` and its process runs
|
||||
:mod:`trio` as a `guest`_ on top of the :mod:`asyncio` loop —
|
||||
letting your trio task tree drive asyncio tasks *in the same
|
||||
process* while the rest of the actor tree stays pure trio. Each
|
||||
trio <-> asyncio task pair is linked with structured concurrency
|
||||
(SC) semantics: error or cancellation on either side tears down
|
||||
both, with the cause translated cross-loop.
|
||||
|
||||
.. d2:: diagrams/infected_aio.d2
|
||||
:caption: A trio guest driving asyncio tasks in one actor.
|
||||
:margin:
|
||||
:alt: trio guest mode inside an asyncio-infected actor
|
||||
|
||||
See ``examples/infected_asyncio_echo_server.py`` for a complete
|
||||
worked example.
|
||||
|
||||
.. currentmodule:: tractor.to_asyncio
|
||||
|
||||
Starting asyncio tasks from trio
|
||||
--------------------------------
|
||||
|
||||
.. autofunction:: open_channel_from
|
||||
|
||||
.. autofunction:: run_task
|
||||
|
||||
.. note::
|
||||
|
||||
:func:`open_channel_from` mirrors the
|
||||
``Portal.open_context()`` handshake: the asyncio side calls
|
||||
``chan.started_nowait(value)`` and that value pops out as
|
||||
``first`` on the trio side. :func:`run_task` is the one-shot
|
||||
form — run a single asyncio-compatible coroutine fn and return
|
||||
its result to trio.
|
||||
|
||||
The inter-loop channel
|
||||
----------------------
|
||||
|
||||
.. autoclass:: LinkedTaskChannel
|
||||
:members: send,
|
||||
receive,
|
||||
wait_for_result,
|
||||
subscribe,
|
||||
started_nowait,
|
||||
send_nowait,
|
||||
get,
|
||||
cancel_asyncio_task,
|
||||
closed
|
||||
|
||||
.. note::
|
||||
|
||||
The trio side uses the async API
|
||||
(:meth:`LinkedTaskChannel.send` /
|
||||
:meth:`LinkedTaskChannel.receive`); the asyncio side uses the
|
||||
loop-safe sync/await mix
|
||||
(:meth:`LinkedTaskChannel.send_nowait` /
|
||||
:meth:`LinkedTaskChannel.get` /
|
||||
:meth:`LinkedTaskChannel.started_nowait`).
|
||||
|
||||
Translated exception types
|
||||
--------------------------
|
||||
|
||||
Cross-loop failures are re-raised on the *other* side as one of
|
||||
these explicit translation types, so you always know which loop
|
||||
actually died first:
|
||||
|
||||
.. autoexception:: tractor._exceptions.AsyncioCancelled
|
||||
|
||||
.. autoexception:: tractor._exceptions.AsyncioTaskExited
|
||||
|
||||
.. autoexception:: tractor._exceptions.TrioCancelled
|
||||
|
||||
.. autoexception:: tractor._exceptions.TrioTaskExited
|
||||
|
||||
.. autoexception:: AsyncioRuntimeTranslationError
|
||||
:show-inheritance:
|
||||
|
||||
Guest-mode entrypoint
|
||||
---------------------
|
||||
|
||||
``run_as_asyncio_guest()`` is the runtime-internal entrypoint that
|
||||
boots trio in `guest`_ mode inside an infected actor — you get it
|
||||
implicitly via ``infect_asyncio=True`` and shouldn't need to call
|
||||
it yourself.
|
||||
|
||||
.. seealso::
|
||||
|
||||
:doc:`/api/core` for the ``infect_asyncio`` spawn flag,
|
||||
:meth:`tractor.Actor.is_infected_aio` for runtime
|
||||
introspection, :doc:`/api/devx` for using the debugger from
|
||||
inside asyncio tasks, and :doc:`/guide/asyncio` for the
|
||||
guided tour.
|
||||
|
||||
.. _guest: https://trio.readthedocs.io/en/stable/reference-lowlevel.html?highlight=guest%20mode#using-guest-mode-to-run-trio-on-top-of-other-event-loops
|
||||
|
|
@ -0,0 +1,76 @@
|
|||
Trio patterns: ``tractor.trionics``
|
||||
===================================
|
||||
|
||||
Sugary structured concurrency (SC) patterns for plain :mod:`trio`
|
||||
code — **no actor runtime required**. These helpers grew out of
|
||||
real distributed-system needs in ``tractor`` apps but every one of
|
||||
them works in a single-process program too; import via
|
||||
``from tractor import trionics``.
|
||||
|
||||
.. currentmodule:: tractor.trionics
|
||||
|
||||
Context-manager helpers
|
||||
-----------------------
|
||||
|
||||
.. autofunction:: gather_contexts
|
||||
|
||||
.. autofunction:: maybe_open_context
|
||||
|
||||
.. autofunction:: maybe_open_nursery
|
||||
|
||||
.. note::
|
||||
|
||||
:func:`gather_contexts` is "a nursery for async context
|
||||
managers": it enters N acms concurrently and yields their
|
||||
values in input order. :func:`maybe_open_context` is the
|
||||
actor-wide cache/multiplex layer on top — the first task pays
|
||||
the acm setup cost, later callers get ``(cache_hit=True, ...)``
|
||||
and share the same value until all users exit.
|
||||
|
||||
Broadcast fan-out
|
||||
-----------------
|
||||
|
||||
.. autofunction:: broadcast_receiver
|
||||
|
||||
.. autoclass:: BroadcastReceiver
|
||||
:members: receive,
|
||||
subscribe,
|
||||
aclose
|
||||
|
||||
.. autoexception:: Lagged
|
||||
:show-inheritance:
|
||||
|
||||
A single-producer, many-consumer broadcast layer over any
|
||||
``trio``-style receive channel: non-lossy for the *fastest*
|
||||
consumer while slower consumers raise :class:`Lagged` (a
|
||||
:class:`trio.TooSlowError` subtype) once they fall behind the
|
||||
internal ring. This is exactly the machinery behind
|
||||
:meth:`tractor.MsgStream.subscribe` — see
|
||||
``examples/streaming_broadcast_fanout.py``.
|
||||
|
||||
ExceptionGroup helpers
|
||||
----------------------
|
||||
|
||||
.. autofunction:: collapse_eg
|
||||
|
||||
.. autofunction:: maybe_raise_from_masking_exc
|
||||
|
||||
.. note::
|
||||
|
||||
:func:`collapse_eg` "un-nests" single-exception
|
||||
:class:`ExceptionGroup` wrappers from strict-eg ``trio``
|
||||
nurseries so your ``except`` clauses match the original error;
|
||||
:func:`maybe_raise_from_masking_exc` surfaces real errors that
|
||||
would otherwise be masked by :class:`trio.Cancelled` during
|
||||
teardown.
|
||||
|
||||
.. seealso::
|
||||
|
||||
:doc:`/api/context` for the IPC-stream consumer of
|
||||
:class:`BroadcastReceiver`, :doc:`/guide/streaming` for
|
||||
fan-out in a worked pipeline, and the `trio docs`_ for the
|
||||
underlying channel and `nursery`_ semantics these helpers
|
||||
compose.
|
||||
|
||||
.. _trio docs: https://trio.readthedocs.io/en/latest/
|
||||
.. _nursery: https://trio.readthedocs.io/en/latest/reference-core.html#nurseries-and-spawning
|
||||
|
|
@ -1,51 +0,0 @@
|
|||
Hot tips for ``tractor`` hackers
|
||||
================================
|
||||
|
||||
This is a WIP guide for newcomers to the project mostly to do with
|
||||
dev, testing, CI and release gotchas, reminders and best practises.
|
||||
|
||||
``tractor`` is a fairly novel project compared to most since it is
|
||||
effectively a new way of doing distributed computing in Python and is
|
||||
much closer to working with an "application level runtime" (like erlang
|
||||
OTP or scala's akka project) then it is a traditional Python library.
|
||||
As such, having an arsenal of tools and recipes for figuring out the
|
||||
right way to debug problems when they do arise is somewhat of
|
||||
a necessity.
|
||||
|
||||
|
||||
Making a Release
|
||||
----------------
|
||||
We currently do nothing special here except the traditional
|
||||
PyPa release recipe as in `documented by twine`_. I personally
|
||||
create sub-dirs within the generated `dist/` with an explicit
|
||||
release name such as `alpha3/` when there's been a sequence of
|
||||
releases I've made, but it really is up to you how you like to
|
||||
organize generated sdists locally.
|
||||
|
||||
The resulting build cmds are approximately:
|
||||
|
||||
.. code:: bash
|
||||
|
||||
python setup.py sdist -d ./dist/XXX.X/
|
||||
|
||||
twine upload -r testpypi dist/XXX.X/*
|
||||
|
||||
twine upload dist/XXX.X/*
|
||||
|
||||
|
||||
|
||||
.. _documented by twine: https://twine.readthedocs.io/en/latest/#using-twine
|
||||
|
||||
|
||||
Debugging and monitoring actor trees
|
||||
------------------------------------
|
||||
TODO: but there are tips in the readme for some terminal commands
|
||||
which can be used to see the process trees easily on Linux.
|
||||
|
||||
|
||||
Using the log system to trace `trio` task flow
|
||||
----------------------------------------------
|
||||
TODO: the logging system is meant to be oriented around
|
||||
stack "layers" of the runtime such that you can track
|
||||
"logical abstraction layers" in the code such as errors, cancellation,
|
||||
IPC and streaming, and the low level transport and wire protocols.
|
||||
|
|
@ -0,0 +1,368 @@
|
|||
Anatomy of the runtime
|
||||
======================
|
||||
|
||||
You can get a long way with ``tractor`` by treating it as "trio_
|
||||
with nurseries that spawn processes". But once you start asking
|
||||
*where does my msg actually go?*, *which process is that?* or
|
||||
*who keeps the phonebook?*, it pays to know how the runtime hangs
|
||||
together. This page walks the stack top to bottom.
|
||||
|
||||
.. d2:: diagrams/runtime_stack.d2
|
||||
:caption: The four runtime layers inside *every* actor process.
|
||||
:alt: layer cake of app tasks, tractor runtime, IPC, OS process
|
||||
:width: 70%
|
||||
|
||||
The layer cake
|
||||
--------------
|
||||
|
||||
Every actor process is the same four-layer sandwich:
|
||||
|
||||
- **your app**: plain ``trio`` tasks, nurseries and cancel
|
||||
scopes; nothing special. ``tractor`` is a `structured
|
||||
concurrency`_ (SC) multi-processing runtime built on trio_ and
|
||||
the whole pitch is that this layer stays *just trio*: no
|
||||
callbacks, no futures, no proxy objects.
|
||||
- **the** ``tractor`` **runtime**: a per-process
|
||||
:class:`tractor.Actor` running the msg loop and RPC task
|
||||
scheduler, plus the user-facing primitives layered on it:
|
||||
:class:`tractor.ActorNursery` (spawning + supervision),
|
||||
:class:`tractor.Portal` (calling into a peer) and
|
||||
:class:`tractor.Context` + :class:`tractor.MsgStream`
|
||||
(SC-linked cross-actor task pairs and streaming).
|
||||
- **IPC channels**: one :class:`tractor.Channel` per connected
|
||||
peer, each wrapping a ``MsgTransport`` that ships
|
||||
msgspec_-typed msgs over TCP or UDS.
|
||||
- **the OS**: one process per actor, started by a swappable
|
||||
spawn backend.
|
||||
|
||||
The property that holds it all together: SC composes *through*
|
||||
the layers. A crash in a leaf actor's app task unwinds that
|
||||
actor's trio tree, ships across its IPC channel as a typed
|
||||
``Error`` msg, and unwinds the parent's trio tree in turn — the
|
||||
"SC-transitive supervision protocol" from the README's pitch.
|
||||
The whole tree cancels and errors like one big trio program; it
|
||||
just happens to be spread across processes.
|
||||
|
||||
One actor, one process, one ``trio.run()``
|
||||
------------------------------------------
|
||||
|
||||
A ``tractor`` "actor" is not a green thread, nor an object with
|
||||
a mailbox, nor a coroutine: it's one OS process running one
|
||||
:func:`trio.run` whose root task boots the runtime machinery —
|
||||
msg loop, RPC task scheduler, IPC server — all embodied by a
|
||||
single :class:`tractor.Actor` instance.
|
||||
|
||||
.. margin:: Shared nothing
|
||||
|
||||
Processes buy you a real `shared nothing architecture`_: no
|
||||
accidentally-shared mutable state, no GIL contention, and
|
||||
every actor can be inspected (or killed) like any other OS
|
||||
process.
|
||||
|
||||
You rarely construct an :class:`~tractor.Actor` yourself; the
|
||||
runtime makes exactly one per process and you grab it with
|
||||
:func:`tractor.current_actor`:
|
||||
|
||||
.. code:: python
|
||||
|
||||
import tractor
|
||||
|
||||
actor = tractor.current_actor() # NoRuntime if none running
|
||||
print(actor.aid.name) # str name, need not be unique
|
||||
print(actor.aid.uuid) # uuid4 str, IS unique
|
||||
print(actor.aid.pid) # the OS pid
|
||||
print(actor.uid) # legacy (name, uuid) pair
|
||||
|
||||
Identity is carried by the ``Aid`` msg-struct (see
|
||||
``tractor.msg.types``): a ``name``/``uuid``/``pid`` triple
|
||||
exchanged in the very first "mailbox handshake" whenever two
|
||||
actors connect. It's what the registrar stores and what shows up
|
||||
in logs and proc-titles. The older ``.uid`` 2-tuple of
|
||||
``(name, uuid)`` predates ``Aid`` and is still pervasive across
|
||||
the codebase; treat it as the legacy spelling of the same
|
||||
identity.
|
||||
|
||||
If this smells like the `actor model`_, sure — but as the
|
||||
README warns, it probably doesn't look like what you *think* an
|
||||
actor model looks like, and that's intentional. Here an "actor"
|
||||
is purely a runtime-unit-of-abstraction: process +
|
||||
``trio.run()`` + IPC machinery.
|
||||
|
||||
IPC: channels, transports, addresses
|
||||
------------------------------------
|
||||
|
||||
Two connected actors talk through a :class:`tractor.Channel`: a
|
||||
duplex, per-peer msg pipe. Each ``Channel`` wraps a
|
||||
``MsgTransport`` instance which does the wire work: framing,
|
||||
encode/decode and the socket itself. The encoding is msgpack
|
||||
(via msgspec_) and *every* msg is an instance of one of the
|
||||
runtime's tagged-union :class:`msgspec.Struct` types: the
|
||||
``Aid`` handshake, ``Start``/``StartAck`` (RPC init),
|
||||
``Started``/``Yield``/``Stop``/``Return`` (the ctx dialog
|
||||
phases), ``Error``, etc. There is no raw-bytes mode; the
|
||||
msg-spec *is* the protocol, which is exactly what lets payloads
|
||||
be type-limited per-context (see ``pld_spec`` in
|
||||
:doc:`/guide/context`).
|
||||
|
||||
Addresses come in two spellings:
|
||||
|
||||
- *unwrapped*: the plain-tuple form you pass to user APIs —
|
||||
``('127.0.0.1', 1616)`` for tcp, or a
|
||||
``(<filedir>, <filename>)`` path-pair for uds;
|
||||
- *wrapped*: the internal ``TCPAddress``/``UDSAddress`` struct
|
||||
types (plus libp2p-style multiaddr helpers over in
|
||||
``tractor.discovery``).
|
||||
|
||||
You only ever need the tuple form; the runtime wraps and
|
||||
unwraps at the boundaries.
|
||||
|
||||
TCP: the boring default
|
||||
***********************
|
||||
|
||||
The default transport (``'tcp'``) binds each actor's IPC server
|
||||
to loopback ``('127.0.0.1', <random port>)`` unless told
|
||||
otherwise, and is the only choice when your tree spans hosts.
|
||||
Nothing exotic: ``trio`` TCP streams + length-prefixed msgpack
|
||||
framing.
|
||||
|
||||
UDS: same-host, creds included
|
||||
******************************
|
||||
|
||||
Pass ``enable_transports=['uds']`` and actors instead talk over
|
||||
unix-domain sockets, with socket files placed in the per-user
|
||||
runtime dir (``$XDG_RUNTIME_DIR/tractor/`` on linux, the
|
||||
``platformdirs`` equivalent elsewhere). Two perks over tcp on a
|
||||
single host:
|
||||
|
||||
- no ports to fight over; addrs are just file paths,
|
||||
- the kernel snitches on your peer for free: the listening side
|
||||
reads the connector's ``pid`` (plus ``uid``/``gid`` on linux)
|
||||
straight off the socket via ``SO_PEERCRED`` /
|
||||
``LOCAL_PEERPID`` — no extra handshake msgs required B)
|
||||
|
||||
.. warning::
|
||||
|
||||
Socket-file lifetime == listening actor lifetime. On
|
||||
listener teardown the runtime ``os.unlink()``\s the socket
|
||||
file immediately, so any *late* connection attempt (say, a
|
||||
sub-actor racing to deregister with a registrar that's
|
||||
already shutting down) fails with ``FileNotFoundError``.
|
||||
And ofc, UDS is same-host only.
|
||||
|
||||
Here's a full actor tree run entirely over uds:
|
||||
|
||||
.. literalinclude:: ../../examples/uds_transport_actor_tree.py
|
||||
:caption: examples/uds_transport_actor_tree.py
|
||||
:language: python
|
||||
|
||||
Picking a transport
|
||||
*******************
|
||||
|
||||
Transport choice is per-actor via the ``enable_transports``
|
||||
kwarg accepted by :func:`tractor.open_root_actor` (and proxied
|
||||
through ``open_nursery()`` when it implicitly boots the
|
||||
runtime), plus per-child via
|
||||
``ActorNursery.start_actor(enable_transports=...)``. Two rules
|
||||
the runtime enforces today:
|
||||
|
||||
- exactly ONE transport per actor: multi-transport actors are
|
||||
on the roadmap but currently raise ``RuntimeError``;
|
||||
- your ``registry_addrs`` protos must all be in
|
||||
``enable_transports``: mismatches fail fast with
|
||||
``ValueError`` instead of (as in darker times) hanging the
|
||||
registrar handshake forever.
|
||||
|
||||
Spawn backends
|
||||
--------------
|
||||
|
||||
How does an actor actually *become* a process? Via a swappable
|
||||
spawn backend, selected with the ``start_method`` kwarg to
|
||||
:func:`tractor.open_root_actor`:
|
||||
|
||||
``'trio'`` (default)
|
||||
The home-grown spawner: re-exec the child as
|
||||
``python -m tractor._child`` using ``trio``'s subprocess
|
||||
machinery, then bootstrap it over the first IPC exchange
|
||||
(the parent ships a ``SpawnSpec`` msg carrying all init
|
||||
state). Supported on all platforms and the most battle
|
||||
tested choice by far.
|
||||
|
||||
``'mp_spawn'`` / ``'mp_forkserver'``
|
||||
The stdlib :mod:`multiprocessing` start-methods of the same
|
||||
names (forkserver is posix-only). Mostly interesting for
|
||||
ecosystem compat and start-up-latency tuning.
|
||||
|
||||
``'subint'`` (experimental, py3.14+)
|
||||
Each actor runs as a `PEP 734`_ sub-interpreter
|
||||
(``concurrent.interpreters``) driven on its own OS thread
|
||||
*inside the parent process*: interpreter-level
|
||||
shared-nothing isolation with much faster start-up. Yes,
|
||||
this bends the one-actor-one-process rule; the rest of the
|
||||
model is unchanged.
|
||||
|
||||
The ``TRACTOR_SPAWN_METHOD`` env-var beats any caller-passed
|
||||
``start_method``, so you can swap backends under an unmodified
|
||||
app:
|
||||
|
||||
.. code:: bash
|
||||
|
||||
TRACTOR_SPAWN_METHOD=mp_forkserver python my_app.py
|
||||
|
||||
One current limitation worth knowing: ``debug_mode=True`` (the
|
||||
crash-to-REPL machinery) is only supported on backends whose
|
||||
child-side runtime is trio-native, e.g. the default ``'trio'``;
|
||||
see :doc:`/guide/debugging` for the deats.
|
||||
|
||||
The registrar
|
||||
-------------
|
||||
|
||||
Discovery needs a phonebook. Every actor, as part of boot,
|
||||
registers its ``Aid`` and bind-addrs with the *registrar*: an
|
||||
otherwise ordinary actor (a :class:`tractor.Registrar`, subtype
|
||||
of :class:`~tractor.Actor`) that keeps the name -> addrs table
|
||||
for the tree; on graceful exit each actor de-registers itself.
|
||||
|
||||
.. margin:: Default registry addrs
|
||||
|
||||
With no ``registry_addrs`` passed:
|
||||
|
||||
- tcp: ``('127.0.0.1', 1616)``
|
||||
- uds: ``registry@1616.sock``
|
||||
in the runtime dir
|
||||
|
||||
Who *is* the registrar? Decided at root boot, rendezvous style.
|
||||
:func:`tractor.open_root_actor` probes each addr in
|
||||
``registry_addrs`` with a quick connect-ping, then:
|
||||
|
||||
- **somebody answered**: this root is a plain actor; it
|
||||
registers with the existing registrar and binds random
|
||||
same-proto addrs for its own IPC server;
|
||||
- **nobody answered**: this root *becomes* the registrar and
|
||||
binds the registry addrs itself.
|
||||
|
||||
So single-program trees need zero config — the root quietly
|
||||
self-appoints — while multi-program setups share a registrar by
|
||||
pointing every program at the same ``registry_addrs``. Pass
|
||||
``ensure_registry=True`` to demand that *this* call create the
|
||||
registry; it raises if the addrs are already served.
|
||||
|
||||
The lookup APIs — :func:`tractor.find_actor`,
|
||||
:func:`tractor.wait_for_actor`, :func:`tractor.query_actor` and
|
||||
:func:`tractor.get_registry` — all consult it (after first
|
||||
checking already-connected peers):
|
||||
|
||||
.. literalinclude:: ../../examples/service_daemon_discovery.py
|
||||
:caption: examples/service_daemon_discovery.py
|
||||
:language: python
|
||||
|
||||
If you bump into "arbiter" in old issues or posts: that's the
|
||||
legacy name for the same thing, surviving in-code only as the
|
||||
``Arbiter = Registrar`` class alias; all current terminology is
|
||||
"registrar"/"registry". Fair warning per the README: this is
|
||||
still a **very naive** discovery sys (no re-election, no gossip
|
||||
protocol... yet) and a registrar is expected to outlive its
|
||||
registrants.
|
||||
|
||||
Runtime env vars
|
||||
----------------
|
||||
|
||||
A few env-vars let you re-tune a whole tree *without touching
|
||||
app code*; each wins over its corresponding kwarg:
|
||||
|
||||
.. list-table::
|
||||
:header-rows: 1
|
||||
:widths: 30 44 26
|
||||
|
||||
* - env-var
|
||||
- effect
|
||||
- vs. kwarg
|
||||
* - ``TRACTOR_LOGLEVEL``
|
||||
- crank (or silence) console-log verbosity for every actor
|
||||
in the tree
|
||||
- beats ``loglevel``
|
||||
* - ``TRACTOR_SPAWN_METHOD``
|
||||
- swap the process spawn backend
|
||||
- beats ``start_method``
|
||||
* - ``TRACTOR_ENABLE_STACKSCOPE``
|
||||
- install the ``SIGUSR1`` task-tree-dump handler in every
|
||||
actor, even outside ``debug_mode`` (see
|
||||
:doc:`/guide/debugging`)
|
||||
- OR'd with ``enable_stack_on_sig``
|
||||
|
||||
Spotting actors from your shell
|
||||
*******************************
|
||||
|
||||
Every sub-actor sets an OS-level proc-title of the form
|
||||
``_subactor[<name>@<pid>]`` (via ``setproctitle``, silently
|
||||
skipped when not installed) so ``ps``/``htop``/``pstree`` show
|
||||
*which actor is which* at a glance. The README's signature
|
||||
incantation — watch a tree build and self-destruct live:
|
||||
|
||||
.. code:: bash
|
||||
|
||||
$TERM -e watch -n 0.1 "pstree -a $$" \
|
||||
& python examples/nested_actor_tree.py \
|
||||
&& kill $!
|
||||
|
||||
For scripting there are two stable cmdline markers:
|
||||
|
||||
.. code:: bash
|
||||
|
||||
pgrep -fa '_subactor\[' # live, titled sub-actors
|
||||
pgrep -fa 'tractor._child' # 'trio'-backend children not
|
||||
# yet (re)titled
|
||||
|
||||
The title also lands in the kernel ``comm`` (truncated to ~15
|
||||
bytes) which survives into zombie state — that's what
|
||||
``tractor``'s own test-harness reapers key off. To be crystal
|
||||
clear about the contract though: you should never *need* a
|
||||
reaper; if you can create zombie child processes (without using
|
||||
a system signal) it **is a bug** — please report it!
|
||||
|
||||
Logging
|
||||
-------
|
||||
|
||||
The runtime logs through a thin adapter over stdlib
|
||||
:mod:`logging` that stamps every record with actor + task info.
|
||||
Two calls get you going:
|
||||
|
||||
.. code:: python
|
||||
|
||||
from tractor.log import get_console_log, get_logger
|
||||
|
||||
log = get_logger(__name__) # actor/task-aware sub-logger
|
||||
get_console_log('info') # attach console handler @ level
|
||||
|
||||
(or just pass ``loglevel='info'`` to
|
||||
:func:`tractor.open_root_actor` and the console handler comes up
|
||||
with the runtime).
|
||||
|
||||
``tractor`` adds custom levels — and matching logger methods —
|
||||
that slot between the stdlib ones so you can dial in *which
|
||||
runtime subsystem* you want to hear from: ``.transport()`` (5),
|
||||
``.runtime()`` (15), ``.devx()`` (17), ``.cancel()`` (22), plus
|
||||
a ``PDB`` (500) level for debugger chatter. E.g.
|
||||
``loglevel='cancel'`` plays the whole cancellation chorus while
|
||||
staying quiet about transport-layer noise. Beyond that
|
||||
``tractor`` isn't opinionated about how you consume logs: it's
|
||||
all stdlib ``logging`` underneath.
|
||||
|
||||
Where to next?
|
||||
--------------
|
||||
|
||||
.. seealso::
|
||||
|
||||
- :doc:`/guide/context` — the SC-linked cross-actor task API
|
||||
that rides on every ``Channel``.
|
||||
- :doc:`/guide/debugging` — ``debug_mode``, the multi-process
|
||||
REPL and ``stackscope`` task-tree dumps.
|
||||
- :doc:`/explain/sc-distributed` — *why*
|
||||
one-actor-one-process, and what kind of "actor model" this
|
||||
is (and isn't).
|
||||
|
||||
.. _structured concurrency: https://en.wikipedia.org/wiki/Structured_concurrency
|
||||
.. _trio: https://github.com/python-trio/trio
|
||||
.. _actor model: https://en.wikipedia.org/wiki/Actor_model
|
||||
.. _shared nothing architecture: https://en.wikipedia.org/wiki/Shared-nothing_architecture
|
||||
.. _msgspec: https://jcristharif.com/msgspec/
|
||||
.. _PEP 734: https://peps.python.org/pep-0734/
|
||||
|
|
@ -0,0 +1,16 @@
|
|||
Big ideas
|
||||
=========
|
||||
The conceptual core of ``tractor``: what *structured
|
||||
concurrency* (SC) means once your "tasks" are whole
|
||||
processes, and how the runtime is layered to deliver
|
||||
that without (much) magic.
|
||||
|
||||
If you only read one page in these docs make it
|
||||
:doc:`sc-distributed`; if you read two, follow it with
|
||||
:doc:`architecture`.
|
||||
|
||||
.. toctree::
|
||||
:maxdepth: 2
|
||||
|
||||
sc-distributed
|
||||
architecture
|
||||
|
|
@ -0,0 +1,207 @@
|
|||
Structured concurrency, across processes
|
||||
=========================================
|
||||
``tractor`` makes one bet: the discipline that made
|
||||
``trio``'s concurrency *readable* — `structured
|
||||
concurrency`_ (SC) — works just as well when the
|
||||
"tasks" are whole OS processes talking over a wire.
|
||||
This page distills what that means, from first
|
||||
principles, with as little ceremony as possible.
|
||||
|
||||
.. margin:: The canon
|
||||
|
||||
If SC is new to you, the seminal `blog post`_ is
|
||||
still the best hour you'll spend on concurrent
|
||||
programming; the `trio docs`_, wikipedia's SC_
|
||||
page and the diagrams over at libdill-docs_ round
|
||||
it out nicely.
|
||||
|
||||
SC in one breath
|
||||
----------------
|
||||
Structured concurrency is the rule that **concurrency
|
||||
gets a scope**: every task is spawned *inside* a block
|
||||
(a ``trio`` *nursery*) and that block **cannot exit
|
||||
until every task it spawned has finished** — returned,
|
||||
errored, or been cancelled.
|
||||
|
||||
That one rule buys you the properties you already
|
||||
rely on in sequential code,
|
||||
|
||||
- a function call is a *black box*: when it returns,
|
||||
everything it started is **done** — no secret
|
||||
background tasks leaking out the sides,
|
||||
- an exception **always has somewhere to go**: up the
|
||||
(task) tree to a parent which is, by construction,
|
||||
still there waiting,
|
||||
- cancellation has a well defined *shape*: cancel a
|
||||
scope and it flows down to every task inside it,
|
||||
and only those.
|
||||
|
||||
In short: your **runtime task tree matches your source
|
||||
code's indentation**. Concurrency you can read.
|
||||
|
||||
The leap: process-shaped tasks
|
||||
------------------------------
|
||||
Now swap "task" for "process".
|
||||
|
||||
A ``tractor`` *actor* is just a Python process running
|
||||
its own ``trio.run()`` — its own private task tree,
|
||||
sharing **nothing** with its siblings. You spawn
|
||||
actors from an :class:`tractor.ActorNursery`, which
|
||||
behaves exactly the way the name implies,
|
||||
|
||||
.. code:: python
|
||||
|
||||
async with tractor.open_nursery() as an:
|
||||
portal = await an.start_actor(
|
||||
'worker',
|
||||
enable_modules=[__name__],
|
||||
)
|
||||
...
|
||||
# ^ block exit == every spawned process has
|
||||
# completed, errored or been cancelled, and
|
||||
# been **reaped**. No exceptions, no zombies.
|
||||
|
||||
so the whole program becomes a *tree of process-trees*
|
||||
— a `supervision tree`_ in erlang-speak — where every
|
||||
arrow means "spawned by, **waited on by**, and
|
||||
supervised by".
|
||||
|
||||
.. d2:: diagrams/actor_tree.d2
|
||||
:caption: A ``tractor`` program: a process tree of
|
||||
``trio`` task trees; every parent **must wait**
|
||||
on its children.
|
||||
:width: 85%
|
||||
|
||||
Causality: no process outlives its parent
|
||||
-----------------------------------------
|
||||
The stdlib's ``multiprocessing`` (and most "job
|
||||
queue" systems) treat child processes as
|
||||
fire-and-forget by default: orphans, zombies, lost
|
||||
tracebacks and ``kill -9`` cleanup scripts are *your*
|
||||
problem. ``tractor`` instead inherits ``trio``'s
|
||||
`causality`_ discipline,
|
||||
|
||||
- **no spawning willy-nilly**: every actor is born
|
||||
from a nursery block with a known parent,
|
||||
- **lifetimes nest**: a sub-actor's entire process
|
||||
tree lives strictly inside its parent's nursery
|
||||
scope,
|
||||
- **teardown is guaranteed**: when a scope exits (or
|
||||
errors, or is cancelled) the runtime SIGINTs,
|
||||
waits, and (only if it must) hard-kills + reaps
|
||||
everything underneath.
|
||||
|
||||
We take the zombie thing personally: *if you can
|
||||
create orphaned child processes without using a
|
||||
system signal, it* **is a bug** — and there's a test
|
||||
suite to back that sentence up.
|
||||
|
||||
Errors always propagate (yes, across the wire)
|
||||
----------------------------------------------
|
||||
In ``trio``, an exception in any task tears through
|
||||
its nursery to a parent that must handle it —
|
||||
`exceptions always propagate`_. ``tractor`` extends
|
||||
the same guarantee across process boundaries: an
|
||||
uncaught error in a remote task is
|
||||
|
||||
1. captured + serialized in the child,
|
||||
2. shipped home over IPC as a typed ``Error`` msg,
|
||||
3. re-raised in the parent **boxed** as a
|
||||
:class:`tractor.RemoteActorError` carrying the
|
||||
original type (``.boxed_type``), a rendered remote
|
||||
traceback, and the erroring actor's id,
|
||||
|
||||
while the supervising nursery applies its (currently
|
||||
*one-cancels-all*, just like ``trio``) strategy to any
|
||||
sibling actors. A crash three processes deep arrives
|
||||
at your shell as one coherent, causal traceback chain
|
||||
— not a silent dead worker and a stuck queue.
|
||||
|
||||
Cancellation is a request, supervision is the rule
|
||||
--------------------------------------------------
|
||||
Cancellation likewise keeps ``trio``'s semantics
|
||||
*verbatim*, just transported: cancelling an actor
|
||||
nursery (or a single :class:`tractor.Context` between
|
||||
two tasks in different processes) sends an explicit
|
||||
cancel **request** over IPC which the remote runtime
|
||||
translates into a real ``trio`` cancel-scope cancel —
|
||||
then *acks back* so the requester can await
|
||||
confirmation within a bounded time. Nothing is ever
|
||||
"just killed" first; graceful always precedes brutal.
|
||||
|
||||
Because every cross-process dialog is a pair of
|
||||
**linked tasks** — one on each side, each inside its
|
||||
own cancel scope — SC stays *transitive*: supervision
|
||||
doesn't stop at the process boundary, it tunnels
|
||||
through every hop of the tree. The wire protocol that
|
||||
enforces this (a small set of typed msgs:
|
||||
``Start``/``Started``/``Yield``/``Stop``/``Return``/
|
||||
``Error``) is detailed in :doc:`/guide/msging` and
|
||||
:doc:`/guide/context`.
|
||||
|
||||
Hold up, is this an "actor model"?
|
||||
----------------------------------
|
||||
Let's stop and ask how many canon actor model papers
|
||||
you've actually read ;)
|
||||
|
||||
From `the author's mouth`_, the **only** requirement
|
||||
is `adherence to`_ the `3 axioms`_::
|
||||
|
||||
In response to a message, an actor may:
|
||||
|
||||
- send a finite number of new messages
|
||||
- create a finite number of new actors
|
||||
- designate a new behavior to process subsequent
|
||||
messages
|
||||
|
||||
``tractor`` adheres — actors exchange msgs, spawn
|
||||
actors, and swap behaviors — **with no extra API** to
|
||||
learn. What we *don't* copy is the cultural baggage:
|
||||
no visible mailboxes, no untyped fire-and-forget
|
||||
``send()``, no "let it crash" without a supervisor
|
||||
that actually hears about it, and definitely no
|
||||
shared-reference *proxy objects* pretending the
|
||||
network isn't there. If our "actors" don't look like
|
||||
what you expected, that's **intentional**: being an
|
||||
actor model is just one property of the system; being
|
||||
*structured* is the point.
|
||||
|
||||
Why processes at all?
|
||||
---------------------
|
||||
Python has a GIL; an actor model by definition shares
|
||||
no state; so the *process* is the natural runtime
|
||||
unit — you get real multi-core parallelism and hard
|
||||
memory isolation for free. But the deeper win is
|
||||
uniformity: because actors only ever talk via msgs
|
||||
over a :class:`tractor.Channel` (TCP, UDS, more to
|
||||
come), the **same code** runs your laptop's worker
|
||||
pool and a multi-host cluster; "distributed" is a
|
||||
deployment detail, not an API.
|
||||
|
||||
It's just ``trio``
|
||||
------------------
|
||||
If you remember one framing, make it this: ``tractor``
|
||||
**is just** ``trio`` — with nurseries that can spawn
|
||||
processes and streams that can cross them. Same
|
||||
nursery discipline, same cancellation semantics, same
|
||||
"how was this not always the API?" feeling, one level
|
||||
up the process tree.
|
||||
|
||||
.. seealso::
|
||||
|
||||
:doc:`/explain/architecture` for how the runtime
|
||||
layers deliver all of the above, and
|
||||
:doc:`/start/quickstart` to feel it in ~20 lines of
|
||||
code.
|
||||
|
||||
.. _structured concurrency: https://en.wikipedia.org/wiki/Structured_concurrency
|
||||
.. _SC: https://en.wikipedia.org/wiki/Structured_concurrency
|
||||
.. _blog post: https://vorpus.org/blog/notes-on-structured-concurrency-or-go-statement-considered-harmful/
|
||||
.. _trio docs: https://trio.readthedocs.io/en/latest/
|
||||
.. _libdill-docs: https://sustrik.github.io/libdill/structured-concurrency.html
|
||||
.. _supervision tree: https://www.erlang.org/doc/design_principles/des_princ.html
|
||||
.. _causality: https://vorpus.org/blog/some-thoughts-on-asynchronous-api-design-in-a-post-asyncawait-world/#c-c-c-c-causality-breaker
|
||||
.. _exceptions always propagate: https://trio.readthedocs.io/en/latest/design.html#exceptions-always-propagate
|
||||
.. _the author's mouth: https://www.youtube.com/watch?v=7erJ1DV_Tlo&t=162s
|
||||
.. _adherence to: https://www.youtube.com/watch?v=7erJ1DV_Tlo&t=1821s
|
||||
.. _3 axioms: https://en.wikipedia.org/wiki/Actor_model#Fundamental_concepts
|
||||
|
|
@ -0,0 +1,309 @@
|
|||
Infected ``asyncio``
|
||||
====================
|
||||
``tractor`` is "just trio_", but the Python world is packed with
|
||||
libraries that only speak ``asyncio``: websocket stacks, vendor
|
||||
SDKs, that one exchange client you can't route around. Rather than
|
||||
make you rewrite them, ``tractor`` lets you *quarantine* them inside
|
||||
a dedicated subactor which runs both event loops at once, with full
|
||||
`structured concurrency`_ (SC) guarantees maintained across the
|
||||
loop boundary *and* the process tree.
|
||||
|
||||
In the project's own words:
|
||||
|
||||
Yes, we spawn a python process, run ``asyncio``, start ``trio``
|
||||
on the ``asyncio`` loop, then send commands to the ``trio``
|
||||
scheduled tasks to tell ``asyncio`` tasks what to do XD
|
||||
|
||||
We call this "infected ``asyncio``" mode: the subactor's stdlib
|
||||
loop runs as the *host* with ``trio`` embedded on top in `guest`_
|
||||
mode, and your ``trio`` tasks drive ``asyncio`` tasks through
|
||||
a linked, SC-supervised, in-memory channel.
|
||||
|
||||
.. d2:: diagrams/infected_aio.d2
|
||||
:caption: One process, two schedulers: ``trio`` rides the
|
||||
``asyncio`` loop as a guest while the parent speaks plain
|
||||
``tractor`` IPC, none the wiser.
|
||||
:alt: parent actor connected over IPC to a subactor whose
|
||||
asyncio loop hosts trio in guest mode, with a
|
||||
LinkedTaskChannel pairing a trio task to an asyncio task
|
||||
|
||||
.. note::
|
||||
|
||||
Infected ``asyncio`` mode is **experimental**: it works (we
|
||||
beat on it plenty) but parts of the API surface and some
|
||||
edge-case semantics are still settling. Got opinions on the
|
||||
interop design? Feel free to sling them in `#273`_!
|
||||
|
||||
How the infection takes hold
|
||||
----------------------------
|
||||
A normal subactor boots by running the ``tractor`` runtime's task
|
||||
tree directly under ``trio.run()``. Pass ``infect_asyncio=True``
|
||||
at spawn time and the child's entrypoint changes shape entirely:
|
||||
|
||||
1. the process starts the stdlib loop via ``asyncio.run()``,
|
||||
2. the first ``asyncio`` task calls
|
||||
``trio.lowlevel.start_guest_run()``, embedding the ``trio``
|
||||
scheduler *inside* the already running ``asyncio`` loop (the
|
||||
upstream `guest`_-mode feature),
|
||||
3. the regular ``tractor`` runtime then boots on the guest
|
||||
``trio`` side and connects back to its parent like any other
|
||||
subactor.
|
||||
|
||||
.. margin:: Symptoms
|
||||
|
||||
Looks like your stdlib event loop has caught a case of "the
|
||||
trios"! Don't worry, you'll barely notice; and if anything
|
||||
gets too bad, your parents will know about it B)
|
||||
|
||||
Both schedulers interleave in a single thread, no GIL gymnastics
|
||||
required. From the rest of the actor tree the infected child is
|
||||
indistinguishable from any other actor: same IPC protocol, same
|
||||
supervision and cancellation semantics, same zombie-safety
|
||||
guarantees. The difference is purely internal: ``trio`` tasks in
|
||||
that process can start and drive ``asyncio`` tasks through the
|
||||
``tractor.to_asyncio`` API.
|
||||
|
||||
Spawning an infected subactor
|
||||
-----------------------------
|
||||
Just flip the flag on :meth:`tractor.ActorNursery.start_actor`:
|
||||
|
||||
.. code:: python
|
||||
|
||||
async with tractor.open_nursery() as an:
|
||||
portal = await an.start_actor(
|
||||
'aio_side',
|
||||
enable_modules=[__name__],
|
||||
infect_asyncio=True,
|
||||
)
|
||||
|
||||
The one-shot convenience ``ActorNursery.run_in_actor()`` accepts
|
||||
the same flag. The ``to_asyncio`` APIs may **only** be called from
|
||||
tasks inside an infected actor; calling them anywhere else raises
|
||||
a loud ``RuntimeError``. You can introspect at runtime with
|
||||
``tractor.current_actor().is_infected_aio()``.
|
||||
|
||||
Linking tasks with ``open_channel_from()``
|
||||
------------------------------------------
|
||||
The core primitive is :func:`tractor.to_asyncio.open_channel_from`,
|
||||
an async context manager which starts your ``asyncio`` function as
|
||||
a real ``asyncio.Task`` and yields a two-way channel linking it to
|
||||
the calling ``trio`` task:
|
||||
|
||||
.. code:: python
|
||||
|
||||
from tractor import to_asyncio
|
||||
|
||||
async with to_asyncio.open_channel_from(
|
||||
aio_main, # async def aio_main(chan, **kwargs)
|
||||
period=0.5, # extra kwargs are passed through
|
||||
) as (chan, first):
|
||||
await chan.send('tick')
|
||||
|
||||
The semantics deliberately mirror the inter-actor ``Context``
|
||||
handshake from :doc:`/guide/context`:
|
||||
|
||||
- the target fn must declare a parameter literally named ``chan``;
|
||||
the runtime injects the shared
|
||||
:class:`~tractor.to_asyncio.LinkedTaskChannel` by keyword.
|
||||
- the ``trio`` side blocks at entry until the ``asyncio`` task
|
||||
calls ``chan.started_nowait(value)``; that value is delivered as
|
||||
``first``, exactly like the ``(ctx, first)`` pair you get from
|
||||
``Portal.open_context()`` after the child calls
|
||||
``ctx.started()``.
|
||||
- a first value **must** be sent from the ``asyncio`` side or the
|
||||
``trio`` side will never unblock.
|
||||
- on block exit the pair is torn down *together*; neither task can
|
||||
outlive the other (more on this below).
|
||||
|
||||
A full example: the echo server
|
||||
-------------------------------
|
||||
Here's the canonical demo, a round-trip echo service where the
|
||||
``asyncio`` task is told what to do by a ``trio`` task which is in
|
||||
turn driven over IPC by the root actor:
|
||||
|
||||
.. literalinclude:: ../../examples/infected_asyncio_echo_server.py
|
||||
:caption: examples/infected_asyncio_echo_server.py
|
||||
:language: python
|
||||
|
||||
What's going on?
|
||||
|
||||
- there are three task layers: the root actor's pure ``trio``
|
||||
task, the infected child's ``trio``-side ``@tractor.context``
|
||||
endpoint (``trio_to_aio_echo_server()``), and the child's
|
||||
``asyncio`` task (``aio_echo_server()``).
|
||||
- two ``started``-style handshakes compose: the aio task's
|
||||
``chan.started_nowait('start')`` unblocks the child's
|
||||
``open_channel_from()`` entry, then the child relays that same
|
||||
value up via ``await ctx.started(first)`` which unblocks the
|
||||
root's ``open_context()`` entry. Synchronization all the way
|
||||
down, er, up.
|
||||
- each round trip flows: root ``stream.send()`` -> IPC -> child
|
||||
``async for msg in stream`` -> ``chan.send(msg)`` -> aio
|
||||
``await chan.get()`` -> ``chan.send_nowait()`` -> child
|
||||
``chan.receive()`` -> ``stream.send(out)`` -> IPC -> root.
|
||||
- when the root breaks out of its stream loop and exits the
|
||||
context block, the child's stream ends, its channel block exits,
|
||||
and the ``asyncio`` task is reaped along with it; the final
|
||||
``portal.cancel_actor()`` then tears down the whole process. No
|
||||
orphaned ``asyncio`` tasks, no zombie procs; if you manage to
|
||||
create either it **is a bug**.
|
||||
|
||||
``LinkedTaskChannel``: one channel, two sides
|
||||
---------------------------------------------
|
||||
The same channel object is shared by both tasks; which methods you
|
||||
call depends on which loop schedules your task. The ``trio`` side
|
||||
gets a standard ``trio.abc.Channel`` interface while the
|
||||
``asyncio`` side gets queue-flavored, mostly-sync methods:
|
||||
|
||||
.. list-table::
|
||||
:header-rows: 1
|
||||
:widths: 14 36 50
|
||||
|
||||
* - side
|
||||
- call
|
||||
- what it does
|
||||
* - ``trio``
|
||||
- ``await chan.send(item)``
|
||||
- ship ``item`` to the ``asyncio`` task (enqueues onto an
|
||||
internal ``asyncio.Queue``).
|
||||
* - ``trio``
|
||||
- ``await chan.receive()``
|
||||
- wait for the next value from the ``asyncio`` side; the
|
||||
channel also supports ``async for``.
|
||||
* - ``trio``
|
||||
- ``await chan.wait_for_result()``
|
||||
- block until the ``asyncio`` task completes; return its
|
||||
final result or raise its (translated) error.
|
||||
* - ``trio``
|
||||
- ``chan.subscribe()``
|
||||
- acm yielding a ``BroadcastReceiver`` so N local tasks can
|
||||
each consume a copy of the inbound stream (see below).
|
||||
* - ``trio``
|
||||
- ``chan.cancel_asyncio_task()``
|
||||
- explicitly request cancellation of the linked ``asyncio``
|
||||
task.
|
||||
* - ``asyncio``
|
||||
- ``chan.started_nowait(value)``
|
||||
- deliver the "first" value; unblocks the ``trio`` side's
|
||||
``open_channel_from()`` entry (mirrors ``ctx.started()``).
|
||||
* - ``asyncio``
|
||||
- ``await chan.get()``
|
||||
- wait for the next value sent from the ``trio`` side.
|
||||
* - ``asyncio``
|
||||
- ``chan.send_nowait(item)``
|
||||
- push a value to the ``trio`` side without blocking.
|
||||
|
||||
Fan-out with ``.subscribe()``
|
||||
*****************************
|
||||
Just like :meth:`tractor.MsgStream.subscribe` does for IPC
|
||||
streams, ``chan.subscribe()`` lets multiple local ``trio`` tasks
|
||||
each receive *every* value sent from the single ``asyncio`` task:
|
||||
|
||||
.. code:: python
|
||||
|
||||
async with chan.subscribe() as bcast:
|
||||
async for msg in bcast:
|
||||
...
|
||||
|
||||
The underlying broadcast machinery is lazily allocated on first
|
||||
use and is *not* reversible for the channel's remaining lifetime,
|
||||
so only reach for it when you actually want the fan-out.
|
||||
|
||||
One-shot calls with ``run_task()``
|
||||
----------------------------------
|
||||
When you just want a single ``asyncio`` result and no streaming
|
||||
dialog, skip the channel ceremony and use
|
||||
:func:`tractor.to_asyncio.run_task`:
|
||||
|
||||
.. code:: python
|
||||
|
||||
import asyncio
|
||||
from tractor import to_asyncio
|
||||
|
||||
async def aio_fetch(url: str) -> str:
|
||||
await asyncio.sleep(0.3) # pretend-IO, aio style
|
||||
return f'<html>sup {url}</html>'
|
||||
|
||||
# from any trio task inside the infected actor:
|
||||
page = await to_asyncio.run_task(aio_fetch, url='https://x.io')
|
||||
|
||||
It schedules the fn as an ``asyncio.Task``, waits for completion
|
||||
and hands the return value back to ``trio``; think of it as the
|
||||
cross-loop sibling of ``ActorNursery.run_in_actor()``. Errors and
|
||||
cancellation are translated exactly as for channels.
|
||||
|
||||
Cross-loop errors and cancellation
|
||||
----------------------------------
|
||||
The paired tasks are *SC linked*: exception and cancel handling
|
||||
tears down **both** sides on any unexpected error or cancellation,
|
||||
in either loop. There is no fire-and-forget mode; a
|
||||
``LinkedTaskChannel`` is a supervision scope just like a
|
||||
``Context`` is across processes.
|
||||
|
||||
Because each loop has its own (incompatible) cancellation and exit
|
||||
machinery, boundary crossings are translated into dedicated
|
||||
exception types, all importable from ``tractor.to_asyncio``:
|
||||
|
||||
.. list-table::
|
||||
:header-rows: 1
|
||||
:widths: 26 22 52
|
||||
|
||||
* - exception
|
||||
- raised in
|
||||
- meaning
|
||||
* - ``AsyncioCancelled``
|
||||
- the ``trio`` task
|
||||
- the linked ``asyncio`` task was cancelled by itself or
|
||||
a 3rd party (i.e. *not* by the ``trio`` side).
|
||||
* - ``AsyncioTaskExited``
|
||||
- the ``trio`` task
|
||||
- the ``asyncio`` task returned/exited early while the
|
||||
``trio`` side still held the link open.
|
||||
* - ``TrioCancelled``
|
||||
- the ``asyncio`` task
|
||||
- the ``trio`` side was cancelled (or crashed) so the
|
||||
``asyncio`` task is being torn down per SC rules.
|
||||
* - ``TrioTaskExited``
|
||||
- the ``asyncio`` task
|
||||
- the ``trio`` side exited gracefully while the ``asyncio``
|
||||
task was still running; a "clean shutdown" signal much
|
||||
like closing a ``trio`` mem-chan.
|
||||
|
||||
By default ``open_channel_from(suppress_graceful_exits=True)``
|
||||
absorbs the two ``*TaskExited`` signals so happy-path teardown
|
||||
stays silent; pass ``False`` when your app wants to handle early
|
||||
peer-exit explicitly.
|
||||
|
||||
Past the task pair, everything composes with the normal actor
|
||||
story: an unhandled ``asyncio`` error is translated into the
|
||||
``trio`` side, propagates out of your ``@tractor.context``
|
||||
endpoint, and arrives at the parent boxed as
|
||||
a :class:`tractor.RemoteActorError`. One SC discipline,
|
||||
end-to-end, across loops *and* processes.
|
||||
|
||||
Breakpoints in ``asyncio`` tasks
|
||||
--------------------------------
|
||||
Yes, the multi-actor REPL works here too. With
|
||||
``debug_mode=True`` enabled on your tree the ``trio`` side of an
|
||||
infected actor can ``await tractor.pause()`` as usual, and with
|
||||
greenback enabled (``maybe_enable_greenback=True``) even the
|
||||
builtin ``breakpoint()`` works from *inside* ``asyncio`` tasks;
|
||||
see ``examples/debugging/asyncio_bp.py`` for the full tour. The
|
||||
root-TTY locking dance behind all this is covered in
|
||||
:doc:`/guide/debugging`.
|
||||
|
||||
Where to next?
|
||||
--------------
|
||||
.. seealso::
|
||||
|
||||
- :doc:`/guide/context` for the inter-actor handshake and
|
||||
streaming APIs which this whole interop layer mirrors.
|
||||
- :doc:`/guide/msging` for typing the payloads you shuttle
|
||||
between actors (and loops).
|
||||
- :doc:`/guide/debugging` for the multi-process REPL that
|
||||
keeps working even when your loop has "the trios".
|
||||
|
||||
.. _trio: https://github.com/python-trio/trio
|
||||
.. _structured concurrency: https://en.wikipedia.org/wiki/Structured_concurrency
|
||||
.. _guest: https://trio.readthedocs.io/en/stable/reference-lowlevel.html?highlight=guest%20mode#using-guest-mode-to-run-trio-on-top-of-other-event-loops
|
||||
.. _#273: https://github.com/goodboy/tractor/issues/273
|
||||
|
|
@ -0,0 +1,285 @@
|
|||
Cancellation and error propagation
|
||||
==================================
|
||||
|
||||
``tractor`` supports ``trio``'s cancellation_ system *verbatim*,
|
||||
then extends it across process boundaries. If you know how to
|
||||
cancel a task in ``trio`` you already know how to cancel an actor —
|
||||
and its whole subtree — in ``tractor``; the runtime's job is making
|
||||
that statement hold over IPC with every structured concurrency (SC)
|
||||
guarantee intact.
|
||||
|
||||
The ground rules,
|
||||
|
||||
- a remote actor is **never** cancelled unless explicitly requested
|
||||
(by a parent or peer), unless supervision demands it (an error
|
||||
triggered one-cancels-all teardown), or unless there's a bug in
|
||||
``tractor`` itself (please report it!),
|
||||
- (remote) errors `always propagate`_ back to the parent
|
||||
supervisor; nothing is silently dropped on the floor,
|
||||
- every spawned process gets reaped no matter how it dies; if you
|
||||
can create a zombie child process (without using a system signal)
|
||||
it **is a bug**.
|
||||
|
||||
``trio`` cancellation, across the wire
|
||||
--------------------------------------
|
||||
|
||||
Locally everything is bog-standard ``trio``: nurseries, cancel
|
||||
scopes, timeouts. ``tractor`` adds exactly one twist: a cancel
|
||||
scope can't physically reach into another process, so the runtime
|
||||
*relays cancellation as messages*. Concretely,
|
||||
|
||||
- cancelling an *actor* means sending it a runtime-cancel request
|
||||
msg; the target then runs its own graceful teardown — cancelling
|
||||
RPC tasks, closing channels, exiting its :func:`trio.run` — and
|
||||
acks the request back to the canceller,
|
||||
- cancelling a single *cross-actor task* works through the
|
||||
:class:`tractor.Context` layer: each ``ctx`` task-pair is
|
||||
cancel-scope-linked over IPC such that either side erroring or
|
||||
cancelling relays an equivalent error to the other side (see
|
||||
:doc:`/guide/context` for the gory details),
|
||||
- a cancel is therefore always a *request with an ack*: the
|
||||
canceller does a **bounded wait** for confirmation and escalates
|
||||
if the peer is unresponsive (see the teardown ladder below).
|
||||
|
||||
One-cancels-all supervision
|
||||
---------------------------
|
||||
|
||||
An :class:`tractor.ActorNursery` supervises subactors `exactly like
|
||||
trio`_ nurseries supervise tasks: when one child errors, the error
|
||||
propagates to the supervising block and **all** sibling subactors
|
||||
get cancelled before the error continues bubbling up the (process)
|
||||
tree.
|
||||
|
||||
.. d2:: diagrams/error_propagation.d2
|
||||
:caption: One-cancels-all: no zombies, no lost errors.
|
||||
:alt: error propagation up a subactor tree
|
||||
:width: 80%
|
||||
|
||||
.. literalinclude:: ../../examples/remote_error_propagation.py
|
||||
:caption: examples/remote_error_propagation.py
|
||||
:language: python
|
||||
|
||||
What's going on here?
|
||||
|
||||
- three healthy actors are spawned as daemons via
|
||||
:meth:`tractor.ActorNursery.start_actor`; left alone they'd
|
||||
happily idle forever,
|
||||
- a fourth actor runs ``assert_err()`` via ``.run_in_actor()`` and
|
||||
promptly trips its ``assert 0``,
|
||||
- the resulting ``AssertionError`` ships back over IPC as a
|
||||
serialized error msg and re-raises *boxed* inside the nursery
|
||||
block as a :class:`tractor.RemoteActorError`,
|
||||
- the nursery reacts like any ``trio`` nursery would: it cancels
|
||||
the three healthy siblings (graceful runtime-cancel requests,
|
||||
acks awaited), reaps all four processes, then re-raises,
|
||||
- ``trio.run(main)`` sees that same ``RemoteActorError`` in the
|
||||
parent-most process — propagation is end-to-end or bust.
|
||||
|
||||
This one-cancels-all style is currently the *only* supervision
|
||||
strategy offered (it's the one ``trio`` gives you); more
|
||||
`erlang strategies`_ are roadmap, see the bottom of this page.
|
||||
|
||||
The boxed-error bestiary
|
||||
------------------------
|
||||
|
||||
All remote failures arrive locally as one of a small set of
|
||||
exception types, each carrying enough metadata to work out *who*
|
||||
failed, *where*, and *why*.
|
||||
|
||||
``RemoteActorError``
|
||||
********************
|
||||
|
||||
The workhorse: a "boxed" exception relayed over IPC from another
|
||||
actor. The original error's type, traceback string and msgdata are
|
||||
preserved so you can pattern-match on what actually went wrong
|
||||
remotely,
|
||||
|
||||
- ``.boxed_type``: the reconstructed **type** of the original
|
||||
remote exception (``ValueError``, ``NameError``, what have you),
|
||||
- ``.src_uid``: the ``(name, uuid)`` pair of the actor where the
|
||||
error *originated*,
|
||||
- ``.relay_uid`` / ``.relay_path``: when an error crosses more than
|
||||
one actor boundary (grandchild -> child -> root) every relaying
|
||||
actor is recorded; multi-hop boxings are lovingly referred to as
|
||||
"inceptions" in the runtime internals,
|
||||
- ``.pformat()``: a rich "tb box" rendering of the remote traceback
|
||||
for your logs or REPL.
|
||||
|
||||
.. code:: python
|
||||
|
||||
try:
|
||||
async with portal.open_context(ep) as (ctx, first):
|
||||
...
|
||||
except tractor.RemoteActorError as rae:
|
||||
if rae.boxed_type is ValueError:
|
||||
... # the remote task raised `ValueError`
|
||||
|
||||
``ContextCancelled``
|
||||
********************
|
||||
|
||||
The cancel-ack for a cross-actor task pair: raised when a
|
||||
:class:`tractor.Context` task is cancelled *by request*. Its
|
||||
``.canceller`` attr is the uid of the actor which **requested** the
|
||||
cancel, which powers the key rule,
|
||||
|
||||
- if **you** requested it (you called
|
||||
:meth:`tractor.Context.cancel`) the resulting ctxc is *absorbed*
|
||||
at ``open_context()`` exit: an expected outcome, not an error,
|
||||
- if **anyone else** did — the peer task, or some third-party actor
|
||||
— it *raises* locally so your code always hears about it.
|
||||
|
||||
The full self- vs. cross-cancel semantics are a core teaching point
|
||||
of :doc:`/guide/context`; go read them there.
|
||||
|
||||
``MsgTypeError``
|
||||
****************
|
||||
|
||||
An IPC-payload "type error": a msg violated the dialog's declared
|
||||
payload spec. See :doc:`/guide/msging` for the typed-messaging
|
||||
system which enforces it.
|
||||
|
||||
``TransportClosed``
|
||||
*******************
|
||||
|
||||
The underlying IPC transport (TCP stream, UDS socket, ...) died or
|
||||
closed out from under a channel. You'll normally only see this
|
||||
surface when a peer hard-exits without any graceful runtime
|
||||
teardown; the supervision machinery treats unexpected transport
|
||||
loss on a busy channel as a failure and tears down accordingly.
|
||||
|
||||
Pick your blast radius
|
||||
----------------------
|
||||
|
||||
Three cancel surfaces, three scopes of effect; choose the smallest
|
||||
hammer that does the job.
|
||||
|
||||
.. list-table::
|
||||
:header-rows: 1
|
||||
:widths: 36 34 30
|
||||
|
||||
* - surface
|
||||
- cancels
|
||||
- typical use
|
||||
* - :meth:`tractor.ActorNursery.cancel`
|
||||
- every subactor in the nursery
|
||||
- whole-tree teardown
|
||||
* - :meth:`tractor.Portal.cancel_actor`
|
||||
- one actor: full runtime + proc
|
||||
- daemon teardown
|
||||
* - :meth:`tractor.Context.cancel`
|
||||
- exactly one remote task
|
||||
- surgical task cancel
|
||||
|
||||
``ActorNursery.cancel()``
|
||||
*************************
|
||||
|
||||
The big red button: gracefully cancel every subactor supervised by
|
||||
the nursery, in parallel, with the escalation discipline below
|
||||
applied per-child. It's invoked for you whenever an error hits the
|
||||
nursery block (one-cancels-all); call it yourself for an orderly
|
||||
early shutdown. Passing ``hard_kill=True`` skips the graceful phase
|
||||
and goes straight to OS-level process termination — rarely what you
|
||||
want outside tests.
|
||||
|
||||
``Portal.cancel_actor()``
|
||||
*************************
|
||||
|
||||
Cancel one **whole actor**: its entire runtime, every task it's
|
||||
scheduled, and (for subactors) the OS process, via a graceful
|
||||
runtime-cancel request,
|
||||
|
||||
.. code:: python
|
||||
|
||||
await portal.cancel_actor() # bounded wait, bool result
|
||||
await portal.cancel_actor(
|
||||
raise_on_timeout=True, # no ack in time?
|
||||
) # -> `ActorTooSlowError`
|
||||
|
||||
The wait for the peer's ack is *bounded* (default
|
||||
``Portal.cancel_timeout = 0.5`` seconds, tunable per call via
|
||||
``timeout=``). By default a missed ack just returns ``False``; with
|
||||
``raise_on_timeout=True`` you instead get an ``ActorTooSlowError``
|
||||
(from ``tractor._exceptions``) so *your* code can escalate per SC
|
||||
discipline — exactly what the nursery's own teardown does
|
||||
internally before resorting to OS-level signalling.
|
||||
|
||||
Note the granularity: this cancels an **actor**, not a task. For
|
||||
one remote task use the ``Context`` layer instead.
|
||||
|
||||
``Context.cancel()``
|
||||
********************
|
||||
|
||||
Request cancellation of exactly one remote task: the peer task of
|
||||
an open :class:`tractor.Context`. Two things to keep straight,
|
||||
|
||||
- it cancels the **remote** side only; a ``Context`` is *not* a
|
||||
:class:`trio.CancelScope` and your local task keeps running until
|
||||
you exit the ``open_context()`` block,
|
||||
- the resulting :class:`tractor.ContextCancelled` is absorbed
|
||||
locally (you asked for it, after all) per the self- vs.
|
||||
cross-cancel rule above.
|
||||
|
||||
Again, :doc:`/guide/context` covers this dance in depth.
|
||||
|
||||
Graceful first, hard as a last resort
|
||||
-------------------------------------
|
||||
|
||||
.. margin:: REPL-safe by design
|
||||
|
||||
The hard-kill path is *skipped* whenever an actor in the tree
|
||||
holds the debug-REPL lock (``debug_mode=True`` flavors):
|
||||
SIGTERM raining down on a tree mid-``pdb`` session would
|
||||
clobber your prompt. See :doc:`/guide/debugging`.
|
||||
|
||||
Every process teardown in ``tractor`` walks the same escalation
|
||||
ladder, top rung first,
|
||||
|
||||
1. **graceful cancel request**: a runtime-cancel msg over IPC; the
|
||||
target actor cancels its tasks, closes its channels and exits
|
||||
its :func:`trio.run` cleanly,
|
||||
2. **soft wait**: the parent waits (bounded) for the child process
|
||||
to exit on its own,
|
||||
3. **SIGTERM**: no ack within the bounded wait (internally an
|
||||
``ActorTooSlowError``) escalates to ``proc.terminate()``,
|
||||
4. **SIGKILL ultimatum**: still alive after the hard-kill timeout
|
||||
(~1.6s)? The runtime logs that the "T-800" has been deployed to
|
||||
collect the zombie and issues ``proc.kill()``. No survivors.
|
||||
|
||||
The result is the **no-zombies guarantee**: ``tractor`` tries to
|
||||
protect you from zombies, no matter what. Quoting the project
|
||||
manifesto,
|
||||
|
||||
If you can create zombie child processes (without using
|
||||
a system signal) it **is a bug**.
|
||||
|
||||
Run the quickstart's self-destructing process-tree demo
|
||||
(``examples/parallelism/we_are_processes.py``, walked through in
|
||||
:doc:`/start/quickstart`) under a ``pstree`` watcher and try to
|
||||
catch a
|
||||
straggler; we'll wait B)
|
||||
|
||||
Roadmap: ``erlang``-style strategies
|
||||
------------------------------------
|
||||
|
||||
One-cancels-all is ``trio``'s strategy and, for now, the only one
|
||||
``tractor`` ships. Pluggable `erlang strategies`_ — one-for-one
|
||||
restarts, rest-for-one, transient/permanent child specs and friends
|
||||
(see the `supervision strategies`_ canon) — are a long-standing
|
||||
roadmap item tracked in `#22`_. If supervisors are your jam that
|
||||
issue is the place to sling opinions.
|
||||
|
||||
.. seealso::
|
||||
|
||||
- :doc:`/guide/context` — the cross-actor task layer where
|
||||
per-task cancellation actually lives,
|
||||
- :doc:`/guide/msging` — the typed msg layer that raises
|
||||
:class:`tractor.MsgTypeError`,
|
||||
- :doc:`/guide/debugging` — what cancellation does (and very
|
||||
carefully does *not* do) while a REPL is up.
|
||||
|
||||
.. _cancellation: https://trio.readthedocs.io/en/latest/reference-core.html#cancellation-and-timeouts
|
||||
.. _exactly like trio: https://trio.readthedocs.io/en/latest/reference-core.html#cancellation-semantics
|
||||
.. _always propagate: https://trio.readthedocs.io/en/latest/design.html#exceptions-always-propagate
|
||||
.. _erlang strategies: https://learnyousomeerlang.com/supervisors
|
||||
.. _supervision strategies: https://www.erlang.org/doc/system/sup_princ.html
|
||||
.. _#22: https://github.com/goodboy/tractor/issues/22
|
||||
|
|
@ -0,0 +1,127 @@
|
|||
Higher-level cluster APIs
|
||||
=========================
|
||||
|
||||
Sometimes you don't want a hand-crafted supervision tree; you want
|
||||
"a pile of workers, one per core, now please". For that there's
|
||||
:func:`tractor.open_actor_cluster`: a convenience wrapper which
|
||||
spawns a *flat* cluster of subactors and hands you back a portal to
|
||||
each,
|
||||
|
||||
.. code:: python
|
||||
|
||||
@acm
|
||||
async def open_actor_cluster(
|
||||
modules: list[str], # RPC allowlist for workers
|
||||
count: int = cpu_count(), # one per core by default
|
||||
names: list[str]|None = None, # default: 'worker_{i}'
|
||||
hard_kill: bool = False, # fwd to `an.cancel()`
|
||||
**runtime_kwargs, # fwd to `open_root_actor()`
|
||||
) -> AsyncGenerator[dict[str, tractor.Portal], None]:
|
||||
|
||||
A cluster in one block
|
||||
----------------------
|
||||
|
||||
.. literalinclude:: ../../examples/quick_cluster.py
|
||||
:caption: examples/quick_cluster.py
|
||||
:language: python
|
||||
|
||||
Walkthrough,
|
||||
|
||||
- ``open_actor_cluster(modules=[__name__])`` concurrently spawns
|
||||
one subactor per detected core (per
|
||||
:func:`multiprocessing.cpu_count`); the ``modules`` list is the
|
||||
usual ``enable_modules``-style capability allowlist so workers
|
||||
may run functions defined in this module,
|
||||
- it yields a ``dict[str, tractor.Portal]`` mapping worker name to
|
||||
portal; note the keys get prefixed with the *spawning* actor's
|
||||
name, so from the root you'll see ``'root.worker_0'``,
|
||||
``'root.worker_1'``, etc.,
|
||||
- a plain :class:`trio.Nursery` then fans out one
|
||||
``portal.run(sleepy_jane)`` per worker; each prints its actor
|
||||
``.uid`` from inside its own process then naps forever — what
|
||||
runs *inside* each worker (and how many tasks you point at it)
|
||||
is entirely yours to compose,
|
||||
- ``tractor.trionics.collapse_eg()`` un-nests the strict
|
||||
``ExceptionGroup`` wrapping so the demo's ``KeyboardInterrupt``
|
||||
surfaces as itself instead of arriving eg-boxed,
|
||||
- on block exit the whole fleet is torn down for you via
|
||||
:meth:`tractor.ActorNursery.cancel`; pass ``hard_kill=True`` at
|
||||
open time to skip straight to OS-level termination instead of
|
||||
the graceful ladder described in :doc:`/guide/cancellation`.
|
||||
|
||||
Sizing, naming, fleet-wide options
|
||||
----------------------------------
|
||||
|
||||
``count`` doesn't have to be core-count and the auto-generated
|
||||
``'worker_{i}'`` names are just the default; pass your own (the
|
||||
length must match ``count`` or you get a ``ValueError``). Any
|
||||
extra ``**runtime_kwargs`` pass through verbatim to
|
||||
:func:`tractor.open_root_actor`, so fleet-wide runtime options are
|
||||
one kwarg away,
|
||||
|
||||
.. code:: python
|
||||
|
||||
async with tractor.open_actor_cluster(
|
||||
modules=['mylib.workers'],
|
||||
count=4,
|
||||
names=['scout', 'miner', 'smelter', 'smith'],
|
||||
debug_mode=True, # whole-fleet crash-to-REPL
|
||||
) as portal_map:
|
||||
...
|
||||
|
||||
From here the composition patterns are the usual ``tractor`` fare:
|
||||
``portal.run()`` for one-shot calls (as in the demo), or — for a
|
||||
persistent bidirectional dialog per worker — concurrently enter N
|
||||
``portal.open_context()`` blocks with
|
||||
``tractor.trionics.gather_contexts()``; see :doc:`/guide/context`
|
||||
for that whole layer.
|
||||
|
||||
Clusters vs. nurseries
|
||||
----------------------
|
||||
|
||||
.. d2:: diagrams/actor_tree.d2
|
||||
:margin:
|
||||
:caption: The general shape: arbitrary nesting. A cluster is
|
||||
this, minus the nesting.
|
||||
:alt: a nested supervision tree of subactors
|
||||
|
||||
``open_actor_cluster()`` is sugar, not a new primitive: under the
|
||||
hood it's just :func:`tractor.open_nursery` plus N concurrent
|
||||
``start_actor()`` calls plus a ``.cancel()`` on the way out. Reach
|
||||
for it when,
|
||||
|
||||
- you want a *flat*, homogeneous fleet (classic worker-pool or
|
||||
map-style fan-out shapes),
|
||||
- "one per core" — or a fixed ``count`` — is the right sizing
|
||||
story,
|
||||
- every child can share the same spawn options.
|
||||
|
||||
Drop down to a raw :class:`tractor.ActorNursery` when the topology
|
||||
gets any fancier: nested trees, heterogeneous children, per-child
|
||||
``debug_mode``/transport/module options, daemons mixed with
|
||||
one-shot workers, and so on (see :doc:`/guide/parallelism` for a
|
||||
hand-rolled pool). Either way the supervision semantics are
|
||||
identical: one-cancels-all error propagation and the no-zombies
|
||||
guarantee from :doc:`/guide/cancellation` apply to clusters too.
|
||||
|
||||
Provisional, by design
|
||||
----------------------
|
||||
|
||||
.. note::
|
||||
|
||||
APIs in this section are considered **provisional**: the
|
||||
signature and semantics of :func:`tractor.open_actor_cluster`
|
||||
may shift as higher-level supervision machinery lands. We
|
||||
encourage you to try it and provide feedback — the
|
||||
`matrix channel`_ is the place to say hi, and `#22`_ tracks the
|
||||
broader supervisor-strategy roadmap.
|
||||
|
||||
.. seealso::
|
||||
|
||||
- :doc:`/guide/parallelism` — worker pools built "by hand" with
|
||||
plain actor nurseries (and why that's easy peasy),
|
||||
- :doc:`/guide/cancellation` — the teardown machinery a cluster
|
||||
inherits for free.
|
||||
|
||||
.. _matrix channel: https://matrix.to/#/!tractor:matrix.org
|
||||
.. _#22: https://github.com/goodboy/tractor/issues/22
|
||||
|
|
@ -0,0 +1,344 @@
|
|||
The ``Context``: a cross-actor task pair
|
||||
=========================================
|
||||
|
||||
If you've written any trio_ you already know the contract: every
|
||||
task lives in a nursery, errors always propagate, cancellation is
|
||||
scoped, and nothing leaks. ``tractor`` extends that exact contract
|
||||
*across processes* — the same guarantees from the seminal
|
||||
`blog post`_, just with the nursery split across two memory
|
||||
domains. The primitive that does it is :class:`tractor.Context`: a
|
||||
**linked pair of tasks**, one in each of two actors, supervised as
|
||||
a single `structured concurrency`_ (SC) scope over IPC.
|
||||
|
||||
.. d2:: diagrams/context_handshake.d2
|
||||
:caption: The SC-transitive supervision protocol, msg by msg.
|
||||
:alt: sequence diagram of the context handshake msg flow
|
||||
|
||||
Pretty much everything else is (or is slated to be) built on this
|
||||
one primitive: ``ActorNursery.run_in_actor()`` is a convenience
|
||||
for "spawn, open a context, await the result, tear down"; plain
|
||||
``Portal.run()`` RPC is planned to be re-implemented on top of it;
|
||||
the multi-process debugger's tree-wide REPL lock rides one. Grok
|
||||
this page and the rest of the library reads as convenience
|
||||
wrappers B)
|
||||
|
||||
The endpoint contract
|
||||
---------------------
|
||||
|
||||
A context endpoint is an async function decorated with
|
||||
:func:`tractor.context` which declares **a param annotated**
|
||||
``tractor.Context`` — any param name you like, the annotation is
|
||||
what's required:
|
||||
|
||||
.. code:: python
|
||||
|
||||
@tractor.context
|
||||
async def trainer(
|
||||
ctx: tractor.Context,
|
||||
model: str,
|
||||
) -> str:
|
||||
await ctx.started('ready')
|
||||
return f'trained {model}'
|
||||
|
||||
.. margin:: Who am I talking to?
|
||||
|
||||
Inside any context task
|
||||
:func:`tractor.current_ipc_ctx` returns the
|
||||
``Context`` bound to the current task; handy
|
||||
in helpers that don't take ``ctx`` explicitly.
|
||||
|
||||
The parent (aka "opener") side invokes it through a
|
||||
:class:`tractor.Portal` using ``Portal.open_context()``, passing
|
||||
any extra kwargs which are shipped over the wire as the remote
|
||||
task's arguments. Since the target fn is referenced by module
|
||||
path, that module must be listed in the peer actor's
|
||||
``enable_modules`` allowlist — RPC capability is always opt-in.
|
||||
|
||||
The decorator also accepts a ``pld_spec``: a type (union) which
|
||||
every payload in the dialog is validated against, upgrading your
|
||||
msgs to a typed contract enforced via :exc:`tractor.MsgTypeError`.
|
||||
Validation strictness follows the "`cheap or nasty`_"
|
||||
`(un)protocol`_ pattern: the one-shot ``Started`` payload gets the
|
||||
nasty treatment (stringently round-trip checked before it's even
|
||||
sent) while high-rate stream payloads stay cheap (checked only
|
||||
receiver side).
|
||||
|
||||
The handshake, on the wire
|
||||
--------------------------
|
||||
|
||||
Every context runs one instance of ``tractor``'s "SC-transitive
|
||||
supervision protocol": a tiny fixed grammar of msgspec_-typed msgs
|
||||
encapsulating *all* RPC dialogs between actors. *Transitive*
|
||||
because each IPC link obeys the same rules a local nursery does —
|
||||
starts are acked, completion is awaited, errors and cancels always
|
||||
relay — so chaining links across a process tree composes into one
|
||||
tree-wide SC scope.
|
||||
|
||||
The figure up top shows a full dialog; in order:
|
||||
|
||||
``Start``
|
||||
sent by ``Portal.open_context()``: "schedule a task running
|
||||
this function with these kwargs".
|
||||
|
||||
``StartAck``
|
||||
the peer runtime confirms the task is scheduled and that the
|
||||
endpoint really is a context-style fn.
|
||||
|
||||
``Started``
|
||||
emitted when the child task calls
|
||||
:meth:`tractor.Context.started`; carries the first payload
|
||||
and unblocks the parent's entry of ``open_context()``.
|
||||
|
||||
``Yield``
|
||||
one per :meth:`tractor.MsgStream.send`, flowing in *either*
|
||||
direction while a stream is open.
|
||||
|
||||
``Stop``
|
||||
graceful end-of-stream: the far side's ``async for``
|
||||
terminates cleanly.
|
||||
|
||||
``Return``
|
||||
the child fn returned; its value becomes the context's final
|
||||
result. If the child raised instead, an ``Error`` msg takes
|
||||
this slot carrying the boxed traceback.
|
||||
|
||||
``ctx.started()``: just like ``task_status.started()``
|
||||
*******************************************************
|
||||
|
||||
The startup phase is a deliberate clone of
|
||||
:meth:`trio.Nursery.start` semantics: the child decides when it's
|
||||
"up", optionally handing back a first value, and the parent stays
|
||||
blocked until that moment:
|
||||
|
||||
.. code:: python
|
||||
|
||||
# trio, in-process
|
||||
first = await nursery.start(child_fn)
|
||||
|
||||
# tractor, cross-process
|
||||
async with portal.open_context(child_fn) as (ctx, first):
|
||||
...
|
||||
|
||||
The ``as (ctx, first)`` tuple is exactly that pair: the
|
||||
:class:`tractor.Context` handle plus whatever value the child
|
||||
passed to ``await ctx.started(value)``. And readiness is not
|
||||
optional — for instance opening a stream before ``.started()``
|
||||
has been called raises a ``RuntimeError``; handshake first, then
|
||||
dialog.
|
||||
|
||||
Bidirectional streaming over a context
|
||||
--------------------------------------
|
||||
|
||||
The canonical ping-pong (design history: `#53`_, `#223`_) — a
|
||||
full-duplex msg stream between a parent and its spawned peer:
|
||||
|
||||
.. literalinclude:: ../../examples/rpc_bidir_streaming.py
|
||||
:caption: examples/rpc_bidir_streaming.py
|
||||
:language: python
|
||||
|
||||
What's going on?
|
||||
|
||||
- ``start_actor()`` spawns the daemon-style subactor
|
||||
``'rpc_server'`` with this very module in its allowlist.
|
||||
|
||||
- ``portal.open_context(simple_rpc, data=10)`` fires the
|
||||
``Start`` msg then blocks until the child task calls
|
||||
``await ctx.started(data + 1)`` — hence ``sent == 11``.
|
||||
|
||||
- both tasks enter ``ctx.open_stream()``: a stream dialog is only
|
||||
fully open once *each* side has entered its block.
|
||||
|
||||
- the parent seeds the first ``'ping'``; each side then echoes
|
||||
the other, one ``Yield`` msg per ``stream.send()``.
|
||||
|
||||
- after the 9th pong the parent ``break``\ s (10 pings sent in
|
||||
total) and exits its stream block, which sends ``Stop``; the
|
||||
child's ``async for`` completes gracefully and its ``else``
|
||||
clause asserts all 10 pings arrived.
|
||||
|
||||
- the 10th in-transit pong? Discarded by the implicit drain at
|
||||
``open_context()`` exit, which runs the dialog down to the
|
||||
child's ``Return`` (here ``None``).
|
||||
|
||||
- daemon actors live until told otherwise:
|
||||
``portal.cancel_actor()`` reaps the subactor explicitly.
|
||||
|
||||
Results: the ``Return`` leg
|
||||
---------------------------
|
||||
|
||||
Every context resolves to a final outcome. Wait on it explicitly
|
||||
from the parent side:
|
||||
|
||||
.. code:: python
|
||||
|
||||
async with portal.open_context(ep) as (ctx, first):
|
||||
...
|
||||
result = await ctx.wait_for_result()
|
||||
|
||||
or just exit the block — ``__aexit__`` implicitly drains the msg
|
||||
flow until the ``Return`` (or ``Error``) arrives, discarding any
|
||||
in-transit ``Yield``\ s on the way. Either way the rule of
|
||||
`causality`_ holds exactly as in a local nursery: **the opener
|
||||
never unblocks before the remote task is done**.
|
||||
|
||||
For post-hoc inspection (think supervision/restart logic) the ctx
|
||||
also exposes ``Context.outcome``, ``.maybe_error`` and
|
||||
``.has_outcome`` — where a "result" might well be the error the
|
||||
dialog ended with.
|
||||
|
||||
Cancellation semantics
|
||||
----------------------
|
||||
|
||||
The part you actually came for; read it twice B)
|
||||
|
||||
A context's two tasks are **cancel-scope-linked across the IPC
|
||||
boundary**: whatever ends one side — error, cancellation, plain
|
||||
old return — is relayed such that the other side ends
|
||||
equivalently. No silent half-open dialogs, no orphaned remote
|
||||
tasks, ever.
|
||||
|
||||
``ctx.cancel()`` cancels the *remote* task
|
||||
*******************************************
|
||||
|
||||
:meth:`tractor.Context.cancel` requests cancellation of the
|
||||
**remote** task only:
|
||||
|
||||
.. code:: python
|
||||
|
||||
async with portal.open_context(ep) as (ctx, first):
|
||||
await accomplish_things(ctx)
|
||||
await ctx.cancel() # remote task, NOT me
|
||||
|
||||
A :class:`tractor.Context` is **not** a :class:`trio.CancelScope`:
|
||||
the call doesn't (and can't) cancel your local task. It sends the
|
||||
cancel request and waits a bounded ``timeout`` for the peer
|
||||
runtime's ``CancelAck``, then your code proceeds to the block exit
|
||||
as normal.
|
||||
|
||||
Compare scopes here: ``Portal.cancel_actor()`` is the big hammer
|
||||
which cancels the peer's **entire runtime** (and thus process);
|
||||
``ctx.cancel()`` is the per-dialog scalpel.
|
||||
|
||||
``ContextCancelled`` and the absorption rule
|
||||
*********************************************
|
||||
|
||||
When a context task gets cancelled *by request* the requestee's
|
||||
runtime reports back with a :exc:`tractor.ContextCancelled`
|
||||
("ctxc") whose ``.canceller`` field holds the uid of the actor
|
||||
which asked. That one field decides what you observe:
|
||||
|
||||
**you requested it**
|
||||
i.e. ``ctxc.canceller == tractor.current_actor().uid``: the
|
||||
ctxc is **absorbed** at ``open_context()`` exit — nothing
|
||||
raises in your block. You asked for a graceful stop and got
|
||||
it; if you care, ``await ctx.wait_for_result()`` hands the
|
||||
ctxc back as a plain *value* for inspection.
|
||||
|
||||
**anyone else requested it**
|
||||
the peer cancelling itself, or some third actor cancelling it
|
||||
from the side: the ctxc **is raised** in your block. From
|
||||
your scope's perspective a task you depend on was killed out
|
||||
from under you and SC demands you hear about it — exactly
|
||||
like a sibling crash in a `nursery`_.
|
||||
|
||||
In code:
|
||||
|
||||
.. code:: python
|
||||
|
||||
try:
|
||||
async with portal.open_context(ep) as (ctx, first):
|
||||
...
|
||||
except tractor.ContextCancelled as ctxc:
|
||||
# can only be a peer- or third-party cancel;
|
||||
# self-requested cancels are absorbed at exit.
|
||||
assert ctxc.canceller != tractor.current_actor().uid
|
||||
|
||||
This self- vs cross-cancel split is what makes explicit teardown
|
||||
*composable*: a supervisor cancels its dialogs without try/except
|
||||
noise, while unexpected cancellation anywhere in the tree still
|
||||
propagates loudly like any other failure.
|
||||
|
||||
.. warning::
|
||||
|
||||
Once ``ctx.cancel()`` has been called the dialog is done: a
|
||||
subsequent ``ctx.open_stream()`` raises ``RuntimeError``.
|
||||
|
||||
For introspection the ctx exposes trio-flavored status props:
|
||||
``.cancel_called`` (this side requested), ``.cancel_acked`` (peer
|
||||
confirmed), ``.cancelled_caught`` and ``.canceller`` —
|
||||
deliberately mirroring :class:`trio.CancelScope` naming.
|
||||
|
||||
Errors propagate, both ways
|
||||
---------------------------
|
||||
|
||||
A crash on either end tears down the pair, SC style:
|
||||
|
||||
- **child raises**: the exception ships back as an ``Error`` msg
|
||||
and re-raises in the parent block boxed as a
|
||||
:exc:`tractor.RemoteActorError`; the original class rides along
|
||||
as ``.boxed_type`` with ``.src_uid`` naming the crashed actor.
|
||||
|
||||
- **parent raises** (or is cancelled) inside the block: an
|
||||
equivalent error/cancel is relayed to the child task so it can
|
||||
never outlive the dialog.
|
||||
|
||||
.. code:: python
|
||||
|
||||
try:
|
||||
async with portal.open_context(ep) as (ctx, first):
|
||||
...
|
||||
except tractor.RemoteActorError as rae:
|
||||
if rae.boxed_type is ValueError:
|
||||
... # remote ValueError, type preserved
|
||||
|
||||
Errors that hop through intermediary actors on their way up the
|
||||
tree ("inceptions" XD) keep the full relay trail in
|
||||
``.relay_uid`` / ``.relay_path``. Payloads violating your declared
|
||||
``pld_spec`` surface as the IPC analog of a ``TypeError``:
|
||||
:exc:`tractor.MsgTypeError`.
|
||||
|
||||
Overruns and backpressure
|
||||
-------------------------
|
||||
|
||||
Stream msgs land in a bounded per-context buffer on the receiver
|
||||
side. A sender that outpaces a non-consuming receiver *overruns*
|
||||
it and the runtime raises :exc:`tractor.StreamOverrun` (also a
|
||||
:exc:`trio.TooSlowError`) instead of buffering without bound — SC
|
||||
discipline applies to memory too.
|
||||
|
||||
Your knobs:
|
||||
|
||||
- ``msg_buffer_size`` on ``ctx.open_stream()`` sizes the buffer.
|
||||
|
||||
- ``allow_overruns=True`` (on ``Portal.open_context()`` and/or
|
||||
``ctx.open_stream()``) opts in to absorbing overflow instead of
|
||||
erroring — reasonable for bursty telemetry-ish feeds, just know
|
||||
you're trading the error for extra buffering.
|
||||
|
||||
One context, one stream
|
||||
-----------------------
|
||||
|
||||
A ``MsgStream`` is strictly **one-shot use**: once it closes —
|
||||
gracefully or not, from either side — it can never be re-opened
|
||||
on the same ctx. Want another round with the same peer? Open a
|
||||
fresh context; they're cheap. The full close-vs-cancel teardown
|
||||
story lives in :doc:`/guide/streaming`.
|
||||
|
||||
.. rubric:: Where to next?
|
||||
|
||||
:doc:`/guide/streaming` covers the rest of the msg-moving story:
|
||||
the legacy one-way API, multi-actor pipelines and in-actor
|
||||
broadcast fan-out. For exhaustive API detail see
|
||||
:class:`tractor.Context`, :class:`tractor.MsgStream` and
|
||||
:exc:`tractor.ContextCancelled`.
|
||||
|
||||
.. _trio: https://github.com/python-trio/trio
|
||||
.. _structured concurrency: https://en.wikipedia.org/wiki/Structured_concurrency
|
||||
.. _blog post: https://vorpus.org/blog/notes-on-structured-concurrency-or-go-statement-considered-harmful/
|
||||
.. _nursery: https://trio.readthedocs.io/en/latest/reference-core.html#nurseries-and-spawning
|
||||
.. _causality: https://vorpus.org/blog/some-thoughts-on-asynchronous-api-design-in-a-post-asyncawait-world/#c-c-c-c-causality-breaker
|
||||
.. _cheap or nasty: https://zguide.zeromq.org/docs/chapter7/#The-Cheap-or-Nasty-Pattern
|
||||
.. _(un)protocol: https://zguide.zeromq.org/docs/chapter7/#Unprotocols
|
||||
.. _msgspec: https://jcristharif.com/msgspec/
|
||||
.. _#53: https://github.com/goodboy/tractor/issues/53
|
||||
.. _#223: https://github.com/goodboy/tractor/issues/223
|
||||
|
|
@ -0,0 +1,545 @@
|
|||
.. _debugging:
|
||||
|
||||
================================
|
||||
"Native" multi-process debugging
|
||||
================================
|
||||
|
||||
``tractor`` ships the thing every ``multiprocessing`` user has
|
||||
wished for and quietly assumed was impossible: a multi-process
|
||||
debugger that *just works*.
|
||||
|
||||
Drop ``await tractor.pause()`` — or, with `greenback`_ installed,
|
||||
a plain builtin ``breakpoint()`` — anywhere in any actor: the
|
||||
root, a child, a grandchild, a sync helper function, even an
|
||||
``asyncio`` task inside an "infected" actor. A full-featured
|
||||
`pdbp`_ REPL opens *in that process*, with syntax-highlighted
|
||||
source listings, tab completion and sticky mode, attached to your
|
||||
one terminal.
|
||||
|
||||
Under the hood every REPL entry acquires a tree-global tty mutex
|
||||
via an IPC request to the root actor, so prompts from concurrent
|
||||
pauses and crashes never interleave. ``ctrl-c`` is shielded while
|
||||
any REPL is live, so a stray ``SIGINT`` can't vaporize the tree
|
||||
out from under you. And in debug mode any uncaught error drops
|
||||
you into a crash REPL *first in the failing child*, then again at
|
||||
each parent as the boxed :class:`~tractor.RemoteActorError` climbs
|
||||
the supervision tree.
|
||||
|
||||
No remote-pdb sockets, no ``set_trace()`` port juggling, no
|
||||
``ptrace`` attach dance: the debugger semantics you already know,
|
||||
transparently extended across an entire process tree. Because
|
||||
``tractor`` is a `structured concurrency`_ (SC) runtime, the
|
||||
debugger composes with supervision instead of fighting it — quit
|
||||
a REPL and errors keep propagating exactly like `trio`_ taught
|
||||
you, ending in clean, zombie-free teardown.
|
||||
|
||||
We're pretty sure it's the (first ever?) "native" debugging UX
|
||||
for multi-process Python B)
|
||||
|
||||
Enabling debug mode
|
||||
-------------------
|
||||
|
||||
Pass ``debug_mode=True`` to your runtime entrypoint, either
|
||||
:func:`tractor.open_nursery` (which forwards it to the implicitly
|
||||
opened root actor) or :func:`tractor.open_root_actor` directly:
|
||||
|
||||
.. code:: python
|
||||
|
||||
async with tractor.open_nursery(
|
||||
debug_mode=True, # arm the whole actor tree
|
||||
) as an:
|
||||
...
|
||||
|
||||
This arms the debug machinery *tree-wide*:
|
||||
|
||||
- crash handling is enabled in every actor: uncaught errors enter
|
||||
a REPL before they propagate,
|
||||
- the internal tty-lock module is auto-exposed over RPC to every
|
||||
subactor (this is what makes the one-terminal handoff work),
|
||||
- console logging is bumped to include ``PDB``-level status msgs
|
||||
so you can see REPL acquire/release events as they happen.
|
||||
|
||||
You can instead flip it on for just one child, letting its
|
||||
siblings crash-and-burn the normal way:
|
||||
|
||||
.. code:: python
|
||||
|
||||
portal = await an.start_actor(
|
||||
'sketchy_worker',
|
||||
debug_mode=True, # OR-ed with the tree-wide flag
|
||||
)
|
||||
|
||||
See ``examples/debugging/per_actor_debug.py`` for a runnable
|
||||
proof of the selective style.
|
||||
|
||||
.. note::
|
||||
|
||||
Debug mode requires the child-side runtime to be
|
||||
``trio``-native so that the tty-lock IPC dialog works; it's
|
||||
currently supported on the ``'trio'`` (default) and
|
||||
``'main_thread_forkserver'`` spawn backends and raises
|
||||
``RuntimeError`` for any other ``start_method``.
|
||||
|
||||
Your first pause point
|
||||
----------------------
|
||||
|
||||
:func:`tractor.pause` is the SC-aware, multi-process spelling of
|
||||
the stdlib's ``breakpoint()``. In the root actor it looks almost
|
||||
boring:
|
||||
|
||||
.. literalinclude:: ../../examples/debugging/root_actor_breakpoint.py
|
||||
:caption: examples/debugging/root_actor_breakpoint.py
|
||||
:language: python
|
||||
|
||||
Run it and you get a ``(Pdb+)`` prompt parked on the ``pause()``
|
||||
line; type ``c`` (continue) and the program finishes normally.
|
||||
|
||||
The exact same call works from *any* subactor, no matter how deep
|
||||
in the tree:
|
||||
|
||||
.. literalinclude:: ../../examples/debugging/subactor_breakpoint.py
|
||||
:caption: examples/debugging/subactor_breakpoint.py
|
||||
:language: python
|
||||
|
||||
Each loop iteration the child actor requests the terminal from
|
||||
the root over IPC, REPLs you, then releases it on ``c``. Pause
|
||||
points are re-entrant-safe: repeat calls from the same task are
|
||||
no-op'd and other local tasks queue politely for the REPL.
|
||||
|
||||
When you get bored, type ``q`` (quit): the resulting
|
||||
``bdb.BdbQuit`` is boxed and shipped to the parent like any other
|
||||
remote error XD — causality is preserved even for your debugging
|
||||
mistakes.
|
||||
|
||||
Crash REPLs: errors climb the tree
|
||||
----------------------------------
|
||||
|
||||
Pause points are only half the story. With debug mode armed, any
|
||||
*uncaught* error anywhere in the tree triggers what we call crash
|
||||
handling mode:
|
||||
|
||||
.. literalinclude:: ../../examples/debugging/subactor_error.py
|
||||
:caption: examples/debugging/subactor_error.py
|
||||
:language: python
|
||||
|
||||
What happens when the child hits that (very intentional)
|
||||
``NameError``:
|
||||
|
||||
1. a REPL opens **in the crashed child first** — you inspect the
|
||||
raising frame, its locals, the works, right inside the failed
|
||||
process,
|
||||
2. when you quit, the error is boxed into a
|
||||
:class:`~tractor.RemoteActorError` and relayed to the parent,
|
||||
3. the parent (here the root) gets *its own* crash REPL with the
|
||||
rendered remote traceback,
|
||||
4. quit again and the nursery tears the tree down — errors keep
|
||||
propagating per SC rules, no zombies left behind.
|
||||
|
||||
You debug the failure at every hop of the supervision tree, which
|
||||
for multi-hop trees means you can chase an error from the leaf
|
||||
that raised it all the way up to the root that supervises it.
|
||||
|
||||
Need to skip REPL entry for certain exceptions? Pass a predicate
|
||||
via ``open_root_actor(debug_filter=...)``; by default
|
||||
cancellation-only exception (groups) don't engage the REPL.
|
||||
|
||||
One terminal, many actors
|
||||
-------------------------
|
||||
|
||||
So how do N processes share one tty without garbling it? The root
|
||||
actor owns stdio for the whole tree and guards it with a FIFO
|
||||
mutex; every subactor REPL entry is an IPC lock request to the
|
||||
root. Exactly one actor-task in the entire tree can own the
|
||||
terminal at a time, so prompts never interleave — ever.
|
||||
|
||||
.. d2:: diagrams/debug_lock.d2
|
||||
:caption: Every REPL entry serializes through the root actor's
|
||||
tty lock; ``continue``-ing one REPL hands the terminal to
|
||||
the next waiter, FIFO style.
|
||||
:alt: sequence diagram of two subactors serializing pdb REPL
|
||||
access through the root actor's tty lock
|
||||
|
||||
The runtime's teardown paths cooperate too: a cancelling parent
|
||||
always waits for any live REPL to release before reaping
|
||||
children, so the debugger never gets yanked out from under you
|
||||
mid-keystroke.
|
||||
|
||||
.. margin:: Watch the tree live
|
||||
|
||||
Run any of these examples with a process-tree watcher in a
|
||||
second terminal and watch actors come and go::
|
||||
|
||||
watch -n 0.1 "pstree -a $$"
|
||||
|
||||
Here's the showpiece: one daemon child re-entering
|
||||
``tractor.pause()`` forever inside a stream, while its sibling
|
||||
repeatedly raises a ``NameError``:
|
||||
|
||||
.. literalinclude:: ../../examples/debugging/multi_daemon_subactors.py
|
||||
:caption: examples/debugging/multi_daemon_subactors.py
|
||||
:language: python
|
||||
|
||||
What you'll actually see
|
||||
************************
|
||||
|
||||
Running it looks *roughly* like this (uids, tracebacks and source
|
||||
listings elided; REPL order can vary with who wins the lock
|
||||
race)::
|
||||
|
||||
$ python examples/debugging/multi_daemon_subactors.py
|
||||
|
||||
Opening a pdb REPL in paused actor: ('bp_forever', '<uuid>')
|
||||
<highlighted source around the `await tractor.pause()` line>
|
||||
(Pdb+) c
|
||||
|
||||
Opening a pdb REPL in crashed actor: ('name_error', '<uuid>')
|
||||
<live traceback: NameError: name 'doggypants' is not defined>
|
||||
(Pdb+) q
|
||||
|
||||
Opening a pdb REPL in crashed actor: ('root', '<uuid>')
|
||||
<boxed RemoteActorError traceback relayed from 'name_error'>
|
||||
(Pdb+) q
|
||||
|
||||
Two (then three) processes, one terminal, zero confusion:
|
||||
``c``-ing out of the paused daemon's REPL releases the tty lock,
|
||||
which immediately hands the prompt to the crashed sibling; quit
|
||||
that and the error propagates as a fully-rendered
|
||||
:class:`~tractor.RemoteActorError` to the parent where one final
|
||||
crash REPL catches it before clean, zombie-free teardown.
|
||||
|
||||
For maximum drama run
|
||||
``multi_nested_subactors_error_up_through_nurseries.py`` (under
|
||||
``examples/debugging/``) which pulls the same trick across a
|
||||
*three-deep* process tree — the tty lock keeps every prompt
|
||||
orderly the whole way up.
|
||||
|
||||
Post-mortem, on demand
|
||||
----------------------
|
||||
|
||||
Crash handling is automatic, but you can also enter a REPL on
|
||||
a live exception *manually* with :func:`tractor.post_mortem` —
|
||||
the actor-aware equivalent of ``pdb.post_mortem()`` — from inside
|
||||
any ``except`` block in any actor (kwargs: ``tb=`` for an
|
||||
explicit traceback, plus ``shield=`` and ``hide_tb=``):
|
||||
|
||||
.. literalinclude:: ../../examples/debugging/pm_in_subactor.py
|
||||
:caption: examples/debugging/pm_in_subactor.py
|
||||
:language: python
|
||||
|
||||
This example demos three REPL entries from one error:
|
||||
|
||||
- the child's manual ``post_mortem()`` inside its ``except``,
|
||||
- the runtime's automatic crash handler in the same child once
|
||||
the error re-raises out of the RPC task,
|
||||
- a manual ``post_mortem()`` in the parent on the received
|
||||
:class:`~tractor.RemoteActorError`, whose ``.boxed_type``
|
||||
faithfully reports the original ``NameError``.
|
||||
|
||||
Pausing from sync code
|
||||
----------------------
|
||||
|
||||
No ``await``? No problem. :func:`tractor.pause_from_sync` brings
|
||||
the same tree-aware REPL to plain synchronous functions — handy
|
||||
when the suspect code is three helpers deep and decidedly not
|
||||
async.
|
||||
|
||||
It's powered by `greenback`_, which is optional, so you need to:
|
||||
|
||||
1. install it (it ships in ``tractor``'s ``sync_pause``
|
||||
dependency group),
|
||||
2. enable it at runtime entry:
|
||||
|
||||
.. code:: python
|
||||
|
||||
async with tractor.open_nursery(
|
||||
debug_mode=True,
|
||||
maybe_enable_greenback=True,
|
||||
) as an:
|
||||
...
|
||||
|
||||
With that armed, sync code can pause from three different caller
|
||||
environments: the main ``trio`` thread, ``trio.to_thread`` bg
|
||||
threads, and (see the next section) ``asyncio`` tasks in infected
|
||||
actors. The greenback "portal" hops back into the ``trio`` loop
|
||||
to do the lock/REPL dance on your behalf:
|
||||
|
||||
.. literalinclude:: ../../examples/debugging/sync_bp.py
|
||||
:caption: examples/debugging/sync_bp.py (the sync fn, excerpt)
|
||||
:language: python
|
||||
:pyobject: sync_pause
|
||||
|
||||
.. literalinclude:: ../../examples/debugging/sync_bp.py
|
||||
:caption: examples/debugging/sync_bp.py (called in a subactor,
|
||||
excerpt)
|
||||
:language: python
|
||||
:pyobject: start_n_sync_pause
|
||||
|
||||
The full script also exercises the hairier root-actor bg-thread
|
||||
cases (and documents their remaining sharp edges) if you want the
|
||||
deep lore.
|
||||
|
||||
The builtin ``breakpoint()`` override
|
||||
*************************************
|
||||
|
||||
When debug mode boots with greenback available, ``tractor`` wires
|
||||
Python's `PEP 553`_ hook so the *builtin* ``breakpoint()`` becomes
|
||||
the actor-aware sync pause, by exporting::
|
||||
|
||||
PYTHONBREAKPOINT=tractor.devx.debug._sync_pause_from_builtin
|
||||
|
||||
That means third-party and legacy code containing bare
|
||||
``breakpoint()`` calls debugs correctly inside your actor tree
|
||||
with zero edits (the override even forwards kwargs like
|
||||
``hide_tb`` to the underlying pause machinery, as shown in the
|
||||
excerpt above).
|
||||
|
||||
.. warning::
|
||||
|
||||
Without greenback (or with ``maybe_enable_greenback=False``,
|
||||
the default), ``debug_mode=True`` instead *blocks* the builtin
|
||||
``breakpoint()``: ``sys.breakpointhook`` is swapped for a
|
||||
raiser and ``PYTHONBREAKPOINT=0`` is set. A naive
|
||||
``breakpoint()`` from some random process would clobber the
|
||||
shared tty, so we'd rather hand you a loud ``RuntimeError``
|
||||
with install instructions.
|
||||
|
||||
Both the hook and the env var are restored to their prior values
|
||||
on runtime exit — see
|
||||
``examples/debugging/restore_builtin_breakpoint.py`` for the
|
||||
proof.
|
||||
|
||||
Breakpoints inside ``asyncio`` tasks
|
||||
------------------------------------
|
||||
|
||||
Yes, even "infected ``asyncio``" actors get the goods. Spawn a
|
||||
child with ``infect_asyncio=True`` (``trio`` runs as a guest on
|
||||
the ``asyncio`` loop inside it) and, with debug mode + greenback
|
||||
armed, every ``asyncio`` task started via ``tractor.to_asyncio``
|
||||
is automatically granted a greenback portal — so a plain builtin
|
||||
``breakpoint()`` (or ``tractor.pause_from_sync()``) inside an
|
||||
``asyncio.Task`` joins the same single-terminal, tree-locked REPL
|
||||
flow:
|
||||
|
||||
.. literalinclude:: ../../examples/debugging/asyncio_bp.py
|
||||
:caption: examples/debugging/asyncio_bp.py
|
||||
:language: python
|
||||
|
||||
Note the interleave: a ``breakpoint()`` on the ``asyncio`` side,
|
||||
``tractor.pause()`` on the ``trio`` side of the same actor, and
|
||||
another pause up in the root — all serialized through the one tty
|
||||
lock with no cross-actor (or cross-event-loop!) clobbering.
|
||||
|
||||
One catch: ``asyncio`` tasks spawned *out-of-band* — i.e. not via
|
||||
``tractor.to_asyncio``, typically by some third-party aio lib —
|
||||
have no portal bestowed, so a sync pause from one raises a loud
|
||||
``RuntimeError`` telling you to ``greenback.ensure_portal()``
|
||||
first. See :ref:`the caveats <debugging-caveats>` below.
|
||||
|
||||
Teardown debugging: the shielded pause
|
||||
--------------------------------------
|
||||
|
||||
`Cancellation`_ is ``trio``'s bread and butter, which raises an
|
||||
awkward question: how do you REPL inside an *already-cancelled*
|
||||
scope, say while debugging some teardown sequence? A bare
|
||||
``pause()`` would itself be cancelled at its next checkpoint.
|
||||
|
||||
The answer is ``await tractor.pause(shield=True)``, which wraps
|
||||
the lock acquisition and REPL session in a shielded cancel scope
|
||||
(``post_mortem(shield=True)`` works the same way):
|
||||
|
||||
.. literalinclude:: ../../examples/debugging/shielded_pause.py
|
||||
:caption: examples/debugging/shielded_pause.py
|
||||
:language: python
|
||||
|
||||
If you forget, ``tractor`` has your back: an unshielded
|
||||
``pause()`` from a cancelled scope fails fast with a hint
|
||||
suggesting ``await tractor.pause(shield=True)`` instead of
|
||||
silently never REPL-ing.
|
||||
|
||||
Go ahead, mash ctrl-c
|
||||
---------------------
|
||||
|
||||
While any REPL is live the runtime installs a custom ``SIGINT``
|
||||
handler tree-wide so that a reflexive ``ctrl-c`` (or five) can't
|
||||
nuke your debug session:
|
||||
|
||||
- the actor that owns the REPL ignores the interrupt and simply
|
||||
re-flushes the prompt — keep mashing, it's fine,
|
||||
- the root actor ignores ``SIGINT`` while a still-IPC-connected
|
||||
child holds the tty lock, so the supervisor won't tear down the
|
||||
tree out from under the debugger,
|
||||
- if the lock state has gone *stale* — the locking child died or
|
||||
its IPC channel dropped — the root cancels the stale lock scope
|
||||
and restores ``trio``'s default handler, so ``ctrl-c`` works
|
||||
again exactly when it should.
|
||||
|
||||
The handler is uninstalled and ``trio``'s own ``SIGINT``
|
||||
semantics restored every time a REPL releases (on ``continue`` /
|
||||
``quit``).
|
||||
|
||||
Live task-tree dumps
|
||||
--------------------
|
||||
|
||||
Sometimes there's no error to catch — the tree is just *hung* and
|
||||
you want to know where. For that ``tractor`` integrates
|
||||
`stackscope`_: send a signal, get a full ``trio`` task-tree dump
|
||||
from every actor in the tree.
|
||||
|
||||
Enable it any of three ways:
|
||||
|
||||
- ``open_root_actor(enable_stack_on_sig=True)`` (or via
|
||||
``open_nursery()`` which forwards it),
|
||||
- set ``TRACTOR_ENABLE_STACKSCOPE=1`` in the env — it's inherited
|
||||
through the process tree so every (sub)actor arms the handler
|
||||
at boot,
|
||||
- call ``tractor.devx.enable_stack_on_sig()`` directly.
|
||||
|
||||
It's intentionally *not* gated on ``debug_mode`` so you can leave
|
||||
it armed in plain runs. Then, when the hang strikes, signal the
|
||||
tree with ``SIGUSR1``.
|
||||
|
||||
.. tip::
|
||||
|
||||
No need to hunt down pids — pattern-match the original cmdline
|
||||
with ``pkill``::
|
||||
|
||||
$ pkill --signal SIGUSR1 -f "python example_script.py"
|
||||
|
||||
Each actor dumps its entire ``trio`` task tree (full nursery
|
||||
recursion via ``stackscope.extract()``) to its tty *and* tees it
|
||||
to ``/tmp/tractor-stackscope-<pid>.log`` — so the trace survives
|
||||
even under captured-stdio harnesses — then relays the signal on
|
||||
to its children, parent-before-child, until the whole tree has
|
||||
reported in.
|
||||
|
||||
Try it yourself with the demo script, which deliberately hangs a
|
||||
subactor in a shielded sleep:
|
||||
|
||||
.. literalinclude:: ../../examples/debugging/shield_hang_in_sub.py
|
||||
:caption: examples/debugging/shield_hang_in_sub.py
|
||||
:language: python
|
||||
|
||||
(That ``trio.CancelScope(shield=True)`` hang also shows off the
|
||||
zombie reaper: ``ctrl-c`` the root and the un-cancellable child
|
||||
still gets hard-reaped — if you can create a zombie it **is a
|
||||
bug**.)
|
||||
|
||||
Crash handling for sync and CLI code
|
||||
------------------------------------
|
||||
|
||||
All of the above rides on the actor runtime, but crashes don't
|
||||
politely wait for ``trio.run()``. For plain sync code — think
|
||||
``typer``/``click`` CLI endpoints, config parsing, anything
|
||||
pre-runtime — there's a sync context manager that wraps the same
|
||||
``pdbp`` post-mortem UX:
|
||||
|
||||
.. code:: python
|
||||
|
||||
from tractor.devx import open_crash_handler
|
||||
|
||||
def main(): # any sync code, no runtime required
|
||||
with open_crash_handler() as boxed:
|
||||
run_my_cli_thing()
|
||||
|
||||
By default any ``BaseException`` (minus an ``ignore`` set
|
||||
defaulting to ``KeyboardInterrupt`` and ``trio.Cancelled``)
|
||||
enters the REPL then re-raises on exit; pass
|
||||
``raise_on_exit=False`` to suppress instead and introspect the
|
||||
``boxed.value`` afterward. The ``catch``/``ignore`` sets and a
|
||||
``repl_fixture`` are all tweakable.
|
||||
|
||||
For the classic ``--pdb`` CLI-flag pattern use the conditional
|
||||
variant:
|
||||
|
||||
.. code:: python
|
||||
|
||||
from tractor.devx import maybe_open_crash_handler
|
||||
|
||||
@app.command() # a `typer` (or `click`) endpoint
|
||||
def cmd(pdb: bool = False):
|
||||
with maybe_open_crash_handler(pdb=pdb):
|
||||
...
|
||||
|
||||
REPL niceties and hooks
|
||||
-----------------------
|
||||
|
||||
Every REPL in this guide is a `pdbp`_ instance (the maintained
|
||||
fork-and-fix of `pdb++`_) pre-configured by ``tractor``:
|
||||
|
||||
- pygments syntax highlighting in listings and tracebacks,
|
||||
- tab completion — including an automatic fixup for
|
||||
libedit-compiled CPythons (e.g. ``uv``-distributed pythons),
|
||||
- sticky mode available via the ``sticky`` command (off by
|
||||
default),
|
||||
- no long-line truncation (terminal resizes behave),
|
||||
- the ``(Pdb+)`` prompt, ``ll``, hidden-frames support and the
|
||||
rest of the ``pdb++`` goodies you may already know.
|
||||
|
||||
Internal runtime frames are traceback-hidden so the REPL lands
|
||||
exactly on *your* ``pause()``-call or crash frame, never on
|
||||
``tractor`` guts.
|
||||
|
||||
Finally, if your app owns the terminal (TUIs, fullscreen
|
||||
dashboards) pass ``repl_fixture=<your ctx mngr>`` to ``pause()``,
|
||||
``post_mortem()`` or ``open_crash_handler()``: it's entered just
|
||||
before the REPL engages (return ``False`` to skip entry entirely)
|
||||
and exited on release — perfect for suspending and restoring your
|
||||
screen around a debug session.
|
||||
|
||||
.. _debugging-caveats:
|
||||
|
||||
Caveats and platform notes
|
||||
--------------------------
|
||||
|
||||
An honest list of the current rough edges:
|
||||
|
||||
- **Windows**: the debugger has no CI coverage on windows at all
|
||||
(the entire test module is skipped there); manual testing has
|
||||
shown it *can* work, but you're in uncharted territory —
|
||||
reports welcome!
|
||||
- **macOS**: supported but with rough edges: special-cased prompt
|
||||
re-flushing for ``bash``-on-darwin, a few tooling tests skipped
|
||||
on CI, and the AF_UNIX ~104-char socket-path limit forces some
|
||||
examples (like the stackscope demo above) to fall back from
|
||||
``'uds'`` to ``'tcp'`` transport. Wonder if all of it'll work
|
||||
on OS X? So do we.
|
||||
- **CPython 3.14**: ``greenback`` (via ``greenlet``) doesn't
|
||||
support 3.14 yet, so ``pause_from_sync()`` and the builtin
|
||||
``breakpoint()`` override are effectively 3.13-only for now.
|
||||
The async APIs — ``pause()`` and ``post_mortem()`` — need no
|
||||
greenback and work everywhere.
|
||||
- **out-of-band** ``asyncio`` **tasks**: sync pauses from aio
|
||||
tasks *not* spawned via ``tractor.to_asyncio`` raise a
|
||||
``RuntimeError`` (no greenback portal was bestowed); run
|
||||
``await greenback.ensure_portal()`` inside such a task first.
|
||||
- **nested-tree ctrl-c edges**: ``SIGINT`` relay through
|
||||
intermediary parents that aren't themselves in debug mode still
|
||||
has known rough edges — see `#320`_.
|
||||
- **captured stdio**: ``pytest``-style output capture can hang a
|
||||
``pause()``; use a real terminal (or a pty à la ``pexpect``,
|
||||
which is how ``tractor``'s own suite drives every one of these
|
||||
examples).
|
||||
|
||||
Where to next?
|
||||
--------------
|
||||
|
||||
.. seealso::
|
||||
|
||||
- :doc:`/guide/context` — the SC-linked cross-actor task API
|
||||
that all the crash-propagation semantics above ride on.
|
||||
- :func:`tractor.pause`, :func:`tractor.post_mortem` and
|
||||
:func:`tractor.pause_from_sync` in the API reference.
|
||||
- ``examples/debugging/`` — 20-odd runnable scripts, nearly
|
||||
every one exercised by the test suite through a real pty.
|
||||
|
||||
.. _structured concurrency:
|
||||
https://en.wikipedia.org/wiki/Structured_concurrency
|
||||
.. _trio: https://github.com/python-trio/trio
|
||||
.. _cancellation: https://trio.readthedocs.io/en/latest/
|
||||
reference-core.html#cancellation-and-timeouts
|
||||
.. _pdbp: https://github.com/mdmintz/pdbp
|
||||
.. _pdb++: https://github.com/pdbpp/pdbpp
|
||||
.. _greenback: https://github.com/oremanj/greenback
|
||||
.. _stackscope: https://github.com/oremanj/stackscope
|
||||
.. _PEP 553: https://peps.python.org/pep-0553/
|
||||
.. _#320: https://github.com/goodboy/tractor/issues/320
|
||||
|
|
@ -0,0 +1,255 @@
|
|||
Actor discovery
|
||||
===============
|
||||
|
||||
So you've spawned a tree of trio-"actors"; now their tasks need to
|
||||
*find* each other to start a dialog. ``tractor`` ships a (self
|
||||
admittedly) **very naive** discovery system which is nonetheless
|
||||
mighty handy for wiring up service-style apps: a built-in
|
||||
*registrar* actor plus a small set of lookup APIs that deliver
|
||||
a live, connected ``Portal`` to whichever peer you're after.
|
||||
|
||||
.. d2:: diagrams/actor_tree.d2
|
||||
:margin:
|
||||
:caption: The root actor doubles as the *registrar* by
|
||||
default; every spawned actor registers itself with it.
|
||||
:alt: actor tree with root acting as registrar
|
||||
|
||||
Because ``tractor`` is built on structured concurrency (SC), the
|
||||
discovery layer is *not* some external etcd/consul-shaped service
|
||||
you have to babysit; it's just another actor — normally the root
|
||||
of your tree — doing a bit of bookkeeping as part of the runtime.
|
||||
|
||||
Every actor phones home
|
||||
-----------------------
|
||||
|
||||
On runtime boot **every** actor self-registers with the registrar:
|
||||
it submits its unique ``(name, uuid)`` identity pair (aka its
|
||||
``uid``) mapped to the list of transport addresses its IPC server
|
||||
is bound to. On graceful teardown it likewise *un*-registers, so
|
||||
the registry tracks the live tree as it grows and shrinks.
|
||||
|
||||
.. note::
|
||||
Actor names are **not** enforced unique — the registry is keyed
|
||||
by the full ``(name, uuid)`` pair. Name-based lookups simply
|
||||
resolve to the *last* registered match, so if you boot five
|
||||
actors all named ``'bob'``, you get the freshest ``'bob'`` B)
|
||||
|
||||
First boot: who's the registrar?
|
||||
--------------------------------
|
||||
|
||||
By default the **root actor** *is* the registrar; subactors
|
||||
inherit the tree's ``registry_addrs`` at spawn time so the whole
|
||||
clan shares one registry with zero config on your part.
|
||||
|
||||
The bootstrap rule inside ``open_root_actor()`` is delightfully
|
||||
simple:
|
||||
|
||||
- on boot, ping every socket addr in ``registry_addrs``; when none
|
||||
are passed the per-transport defaults are used: for TCP the
|
||||
loopback ``('127.0.0.1', 1616)``, for UDS a
|
||||
``registry@1616.sock`` file,
|
||||
|
||||
- if a registrar answers, you boot as a plain (non-registrar) root
|
||||
actor and register with the *existing* registry; your own IPC
|
||||
server binds random same-transport addrs instead,
|
||||
|
||||
- if **nothing answers, congratulations: you just became the
|
||||
registrar**. Your transport server binds the registry addrs
|
||||
themselves and you start serving lookups for everyone else.
|
||||
|
||||
Pass ``ensure_registry=True`` when your program *requires* being
|
||||
the one-and-only registrar; boot then fails loudly with a
|
||||
``RuntimeError`` if some other process already bound the registry
|
||||
socket(s).
|
||||
|
||||
Looking up actors
|
||||
-----------------
|
||||
|
||||
All lookup APIs are async context managers, so the SC rule you
|
||||
already know from the rest of ``tractor`` holds here too: any
|
||||
delivered portal (and its underlying IPC channel) is scoped to
|
||||
your ``async with`` block — no dangling connections.
|
||||
|
||||
``find_actor()``
|
||||
****************
|
||||
|
||||
The workhorse: ask the registrar for ``name`` and connect a portal
|
||||
to the match, or get ``None`` back when nobody's home:
|
||||
|
||||
.. code:: python
|
||||
|
||||
async with tractor.find_actor('data_feed') as portal:
|
||||
if portal is None:
|
||||
... # not registered anywhere; maybe spawn it?
|
||||
else:
|
||||
await portal.run(do_stuff)
|
||||
|
||||
Knobs worth knowing:
|
||||
|
||||
- ``registry_addrs=[...]``: query specific (possibly multiple,
|
||||
possibly remote) registrars instead of your tree's default,
|
||||
|
||||
- ``only_first=False``: deliver a ``list[Portal]`` of *all*
|
||||
matches found across the queried registrars instead of just the
|
||||
first,
|
||||
|
||||
- ``raise_on_none=True``: raise a ``RuntimeError`` instead of
|
||||
yielding ``None`` when no match is found — for when absence is
|
||||
a hard error in your app.
|
||||
|
||||
``wait_for_actor()``
|
||||
********************
|
||||
|
||||
Blocks until *someone* registers under ``name``, then yields a
|
||||
portal to that registree. Perfect for "wait for my sibling service
|
||||
to come up" sequencing:
|
||||
|
||||
.. code:: python
|
||||
|
||||
async with tractor.wait_for_actor('service') as portal:
|
||||
await portal.run(some_fn)
|
||||
|
||||
``query_actor()``
|
||||
*****************
|
||||
|
||||
A lookup *without* connecting to the target: yields an
|
||||
``(addr, reg_portal)`` pair where ``addr`` is the peer's preferred
|
||||
transport address, or ``None`` when nothing is registered under
|
||||
that name. Use it for liveness peeks or to log where a service
|
||||
lives without actually dialing it up.
|
||||
|
||||
``get_registry()``
|
||||
******************
|
||||
|
||||
Yields a portal straight to the registrar actor itself — or a
|
||||
``LocalPortal`` shim when the calling actor *is* the registrar
|
||||
(no IPC required to talk to yourself, hopefully).
|
||||
|
||||
Fast paths and address preference
|
||||
---------------------------------
|
||||
|
||||
Before doing any RPC to the registrar, every lookup first scans
|
||||
the calling actor's *already-connected peers*: if you have a live
|
||||
channel to an actor named ``name`` you get a portal over it
|
||||
immediately, no registrar round-trip at all.
|
||||
|
||||
When a registry entry holds *multiple* addresses (a multihomed
|
||||
actor) the "best" one is chosen by locality:
|
||||
|
||||
1. UDS — same-host guaranteed, lowest overhead,
|
||||
|
||||
2. local TCP — loopback or any of this host's own interface
|
||||
addrs,
|
||||
|
||||
3. remote TCP — the only option when actually distributed.
|
||||
|
||||
Within a tier the most recently registered addr wins. Stale
|
||||
entries (an addr that no longer accepts connections) are detected
|
||||
on use and deleted from the registrar's table on your behalf.
|
||||
|
||||
Demo: register and find a service
|
||||
---------------------------------
|
||||
|
||||
The simplest possible spin: start a subactor, ask the registrar
|
||||
where it lives, and wait on its registration:
|
||||
|
||||
.. literalinclude:: ../../examples/service_discovery.py
|
||||
:caption: examples/service_discovery.py
|
||||
:language: python
|
||||
|
||||
The daemon-service pattern
|
||||
--------------------------
|
||||
|
||||
The classic deployment shape: a long-lived daemon actor serves
|
||||
RPC, later-running code discovers it by name, calls in, and
|
||||
gracefully cancels it when the job is done:
|
||||
|
||||
.. literalinclude:: ../../examples/service_daemon_discovery.py
|
||||
:caption: examples/service_daemon_discovery.py
|
||||
:language: python
|
||||
|
||||
Note the teardown ordering — *graceful cancel* of the daemon via
|
||||
its portal is part of the pattern; under SC a "service" is still
|
||||
somebody's child and somebody is responsible for reaping it.
|
||||
|
||||
Joining an existing tree from outside
|
||||
-------------------------------------
|
||||
|
||||
Discovery isn't limited to a single program: any standalone script
|
||||
can join a running tree by booting its *own* root actor pointed at
|
||||
the existing registrar:
|
||||
|
||||
.. code:: python
|
||||
|
||||
import trio
|
||||
import tractor
|
||||
|
||||
async def main():
|
||||
async with (
|
||||
# contact the live tree's registrar
|
||||
tractor.open_root_actor(
|
||||
registry_addrs=[('127.0.0.1', 1616)],
|
||||
),
|
||||
tractor.find_actor('data_feed') as portal,
|
||||
):
|
||||
... # RPC away like you were born here
|
||||
|
||||
trio.run(main)
|
||||
|
||||
Per the bootstrap rules above, if the registrar at those addrs is
|
||||
*not* reachable this process simply becomes its own (registrar)
|
||||
root — so the same code works standalone and as a tree-joiner.
|
||||
|
||||
"Arbiter"? A legacy naming note
|
||||
-------------------------------
|
||||
|
||||
In older releases (and many an old blog post or issue thread) the
|
||||
registrar actor was called the *arbiter*, with matching APIs like
|
||||
``get_arbiter()`` and an ``arbiter_addr`` argument. All of that
|
||||
terminology is retired: it's *registrar*/*registry* everywhere now
|
||||
(``registry_addrs``, ``get_registry()``, ...) and the
|
||||
``tractor.Arbiter`` export survives only as a back-compat alias of
|
||||
``tractor.Registrar``. If you see "arbiter" somewhere, mentally
|
||||
substitute "registrar" and you're up to date.
|
||||
|
||||
.. note::
|
||||
Multihoming nerds: ``tractor.discovery`` also ships
|
||||
libp2p-style *multiaddr* helpers — ``mk_maddr()`` and
|
||||
``parse_maddr()`` — for describing transport endpoints as
|
||||
structured strings.
|
||||
|
||||
Very naive, very honest
|
||||
-----------------------
|
||||
|
||||
To be clear, this is a **very naive** discovery system: one
|
||||
process-tree-local registrar holding a dict, no replication, no
|
||||
re-election when it dies, no cross-host propagation. That's
|
||||
intentional (for now); it covers the "wire up my services on this
|
||||
host" case without dragging in a consensus protocol.
|
||||
|
||||
On the roadmap (issue `#216`_ tracks a chunk of it):
|
||||
|
||||
- registrar high(er)-availability: staying up past tree teardown
|
||||
and re-election,
|
||||
|
||||
- a `gossip protocol`_ for decentralized cross-host discovery (the
|
||||
zguide's `discovery`_ chapter is the spiritual reference),
|
||||
|
||||
- `modern protocol`_ (rendezvous) style meet-up points.
|
||||
|
||||
If any of that scratches your itch, the issue tracker would love
|
||||
to hear from you.
|
||||
|
||||
.. seealso::
|
||||
- :doc:`/guide/testing` — watching live actor trees (and their
|
||||
registrar) while the test suite or your app runs.
|
||||
- API refs: :func:`tractor.find_actor`,
|
||||
:func:`tractor.wait_for_actor`,
|
||||
:func:`tractor.query_actor`,
|
||||
:func:`tractor.get_registry`,
|
||||
:class:`tractor.Registrar`.
|
||||
|
||||
.. _gossip protocol: https://en.wikipedia.org/wiki/Gossip_protocol
|
||||
.. _modern protocol: https://en.wikipedia.org/wiki/Rendezvous_protocol
|
||||
.. _discovery: https://zguide.zeromq.org/docs/chapter8/#Discovery
|
||||
.. _#216: https://github.com/goodboy/tractor/issues/216
|
||||
|
|
@ -0,0 +1,52 @@
|
|||
Guides
|
||||
======
|
||||
Task-focused walkthroughs of every major ``tractor``
|
||||
subsystem, each built around real, *test-suite
|
||||
verified* example scripts from the repo's
|
||||
``examples/`` dir (we never copy-paste code into
|
||||
docs; what you read is what CI runs).
|
||||
|
||||
Roughly in "first date to long term relationship"
|
||||
order,
|
||||
|
||||
- :doc:`spawning` — actor nurseries, daemons +
|
||||
one-shot workers, process lifetimes.
|
||||
- :doc:`rpc` — portals: calling into another
|
||||
process like it's a local ``await``.
|
||||
- :doc:`context` — the cross-actor task-pair
|
||||
primitive at the heart of modern ``tractor``.
|
||||
- :doc:`streaming` — one-way and bidirectional
|
||||
msg streams between actors.
|
||||
- :doc:`cancellation` — supervision, error
|
||||
boxing + propagation, teardown discipline.
|
||||
- :doc:`debugging` — the multi-process native
|
||||
REPL debugger; our flagship DX feature B)
|
||||
- :doc:`discovery` — the registrar, finding
|
||||
actors by name, service patterns.
|
||||
- :doc:`clustering` — quick flat process
|
||||
clusters via one ``async with``.
|
||||
- :doc:`parallelism` — worker pools without
|
||||
pools; a ``concurrent.futures`` re-think.
|
||||
- :doc:`asyncio` — "infected asyncio" mode:
|
||||
SC-supervise ``asyncio`` tasks from ``trio``.
|
||||
- :doc:`msging` — typed IPC payloads, the wire
|
||||
msg-spec and custom codecs.
|
||||
- :doc:`testing` — running + monitoring the
|
||||
test suite (and testing your own actor apps).
|
||||
|
||||
.. toctree::
|
||||
:hidden:
|
||||
:maxdepth: 1
|
||||
|
||||
spawning
|
||||
rpc
|
||||
context
|
||||
streaming
|
||||
cancellation
|
||||
debugging
|
||||
discovery
|
||||
clustering
|
||||
parallelism
|
||||
asyncio
|
||||
msging
|
||||
testing
|
||||
|
|
@ -0,0 +1,260 @@
|
|||
Typed messaging
|
||||
===============
|
||||
Every value that crosses an actor boundary rides inside a typed
|
||||
msg. ``tractor`` ships a small, fixed family of msg types, the
|
||||
"SC-transitive supervision protocol", which encapsulates *all*
|
||||
RPC dialogs in the tree such that `structured concurrency`_ (SC)
|
||||
semantics -- parent-child task linkage, error propagation,
|
||||
graceful cancellation -- hold across every process hop. On top of
|
||||
that
|
||||
protocol you can layer **your own** payload type contracts,
|
||||
per-endpoint, and have them enforced at runtime by the codec.
|
||||
|
||||
.. note::
|
||||
|
||||
Older posts and readmes claim ``tractor`` "uses
|
||||
``msgpack``(-python)" on the wire. The wire *encoding* is still
|
||||
msgpack, but since ``0.1.0a5`` all codec work is done by
|
||||
msgspec_ against a strictly-typed, tagged-union msg-spec;
|
||||
neither ``msgpack-python`` nor ``u-msgpack`` are involved.
|
||||
|
||||
The wire format
|
||||
---------------
|
||||
Each protocol msg is a :class:`msgspec.Struct` subtype declared
|
||||
with ``tag=True, tag_field='msg_type'``, so the full set decodes
|
||||
as a `tagged union`__ with zero dispatch code of our own. The
|
||||
payload-carrying msgs all inherit from ``PayloadMsg`` which boxes:
|
||||
|
||||
__ https://jcristharif.com/msgspec/structs.html#tagged-unions
|
||||
|
||||
- ``.cid`` -- the "context id" identifying which dialog (i.e.
|
||||
which ``Context``) the msg belongs to,
|
||||
- ``.pld`` -- the *payload*, aka your app's actual data.
|
||||
|
||||
Decoding is deliberately two-layered:
|
||||
|
||||
- the **transport codec** decodes only the protocol *envelope*,
|
||||
intentionally leaving ``.pld`` as raw bytes
|
||||
(:class:`msgspec.Raw`),
|
||||
- a **per-context payload-receiver** (the internal ``PldRx``) then
|
||||
decodes each ``.pld`` against *that* dialog's user-defined type
|
||||
spec.
|
||||
|
||||
This split is what lets every ``Context`` carry its own msg-spec
|
||||
without reconfiguring the shared transport, keeps the runtime's
|
||||
own traffic immune to your app's spec choices, and makes any
|
||||
validation failure attributable to exactly one dialog (and thus
|
||||
one task pair) instead of nuking the whole channel.
|
||||
|
||||
The protocol family
|
||||
-------------------
|
||||
The entire msg-spec is ten types, all importable from
|
||||
``tractor.msg`` (defined in ``tractor.msg.types``):
|
||||
|
||||
.. list-table::
|
||||
:header-rows: 1
|
||||
:widths: 18 82
|
||||
|
||||
* - msg type
|
||||
- role
|
||||
* - ``Aid``
|
||||
- actor-identity handshake; the first thing two peers
|
||||
exchange on connect (name, uuid, pid).
|
||||
* - ``SpawnSpec``
|
||||
- parent -> child runtime config sent right after ``Aid``:
|
||||
enabled modules, registry/bind addrs, runtime vars.
|
||||
* - ``Start``
|
||||
- request to remotely schedule an RPC task: target
|
||||
namespace + func name, kwargs and the caller's uid.
|
||||
* - ``StartAck``
|
||||
- the callee's ack declaring the endpoint's "functype":
|
||||
``asyncfunc``, ``asyncgen`` or ``context``.
|
||||
* - ``Started``
|
||||
- the first value passed to ``ctx.started()``; completes
|
||||
the context handshake.
|
||||
* - ``Yield``
|
||||
- one streamed value per ``MsgStream.send()`` call.
|
||||
* - ``Stop``
|
||||
- graceful stream termination; the IPC rendition of
|
||||
``StopAsyncIteration``.
|
||||
* - ``Return``
|
||||
- the final return value of the remote task fn.
|
||||
* - ``CancelAck``
|
||||
- ``bool`` result of a runtime cancel-request; always
|
||||
decodable so graceful cancellation can never be broken
|
||||
by a custom msg-spec.
|
||||
* - ``Error``
|
||||
- a boxed remote exception (src uid, relay path, tb str,
|
||||
..) relayed for local re-raise as
|
||||
:class:`tractor.RemoteActorError`.
|
||||
|
||||
Squint and you'll see an SC task scope serialized onto the wire:
|
||||
every dialog opens with ``Start``/``StartAck`` (plus ``Started``
|
||||
for ``@tractor.context`` endpoints), optionally streams
|
||||
``Yield``-s until a ``Stop``, and **always** terminates with
|
||||
exactly one of ``Return``, ``Error`` or ``CancelAck``. That 1:1
|
||||
mapping of msg sequence onto a cross-process task pair is why we
|
||||
call the protocol *SC-transitive*: supervision semantics survive
|
||||
every hop of the tree. In `(un)protocol`_ terms it's our "SC
|
||||
dialog un-protocol".
|
||||
|
||||
For introspection the union alias ``tractor.msg.MsgType``, the
|
||||
list ``__msg_types__`` and the spec alias ``__msg_spec__`` are
|
||||
all exported.
|
||||
|
||||
Payload typing with ``pld_spec``
|
||||
--------------------------------
|
||||
By default ``.pld`` may be any msgspec-supported type, i.e. the
|
||||
spec is ``Any``. To constrain a single endpoint's dialog, pass
|
||||
a type (union) to the decorator:
|
||||
``@tractor.context(pld_spec=MyStruct|None)``. The spec then
|
||||
applies to all payload-carrying msgs of that dialog --
|
||||
``Started``, ``Yield`` and ``Return`` -- on both sides of the
|
||||
IPC. Pro tip: keep ``None`` in your union since most endpoints
|
||||
implicitly ``return None`` and a bare ``ctx.started()`` ships
|
||||
``None`` too.
|
||||
|
||||
.. literalinclude:: ../../examples/typed_payloads.py
|
||||
:caption: examples/typed_payloads.py
|
||||
:language: python
|
||||
|
||||
What's going on?
|
||||
|
||||
- the payload schema is just a :class:`msgspec.Struct` subtype;
|
||||
anything msgspec can tag and decode works, including unions
|
||||
of structs, builtins and containers.
|
||||
- decorating with ``@tractor.context(pld_spec=...)`` attaches the
|
||||
spec to the endpoint; both peers' payload-receivers now decode
|
||||
this dialog's payloads against it. No spec sharing files, no
|
||||
IDL compiler, the contract *is* the Python type.
|
||||
- the happy path looks identical to untyped code: the child calls
|
||||
``await ctx.started(<conforming value>)``, streams or returns
|
||||
more conforming values, and the parent receives fully decoded
|
||||
struct instances (not dicts!) on its side.
|
||||
- the sad path is the point: shipping a value *outside* the spec
|
||||
raises :class:`tractor.MsgTypeError`, which the example catches
|
||||
to show off the failure mode; see the anatomy section below for
|
||||
exactly where it gets raised.
|
||||
|
||||
Where validation happens: cheap-or-nasty
|
||||
----------------------------------------
|
||||
A naive impl would validate every payload on both send *and*
|
||||
receive, doubling your codec bill exactly where throughput
|
||||
matters most. Instead ``tractor`` follows the 0mq lords'
|
||||
"`cheap or nasty`_" pattern: be **nasty** (strict, eager,
|
||||
expensive) on the rare control msgs and **cheap** (lazy, fast) on
|
||||
the high-rate stream path.
|
||||
|
||||
- ``Started`` is the *only* payload that gets the full nasty
|
||||
treatment: ``ctx.started(value)`` stringently
|
||||
**roundtrip-checks** the encoded msg against the dialog's spec
|
||||
*before* sending, so a non-conforming first value raises
|
||||
:class:`tractor.MsgTypeError` immediately in the child and
|
||||
never even hits the wire. (You can opt out per-call with
|
||||
``ctx.started(..., validate_pld_spec=False)`` if you measure
|
||||
a real cost.)
|
||||
- ``Yield`` payloads are **never** checked inside
|
||||
``MsgStream.send()``; they're validated receiver-side on each
|
||||
``MsgStream.receive()``. A violation raises a ``MsgTypeError``
|
||||
in the receiver *and* relays an ``Error`` msg back so the
|
||||
offending sender gets one raised too.
|
||||
- the remaining control msgs (``Start``, ``Return``) are likewise
|
||||
validated such that violations raise in the **sending** actor,
|
||||
pointing the traceback at the code that actually goofed.
|
||||
|
||||
Anatomy of a ``MsgTypeError``
|
||||
-----------------------------
|
||||
:class:`tractor.MsgTypeError` is the IPC equivalent of a builtin
|
||||
``TypeError``: a ``RemoteActorError`` subtype raised whenever
|
||||
a msg fails to decode against the active spec. The useful bits:
|
||||
|
||||
- ``.bad_msg`` -- the offending msg instance (reconstructed from
|
||||
its wire form when necessary) so you can inspect the actual
|
||||
``.pld`` that broke the contract.
|
||||
- ``.expected_msg_type`` -- the protocol msg type the bad msg was
|
||||
(supposed to be) decoded as, e.g. ``Started[Point]``.
|
||||
- plus the standard ``RemoteActorError`` goodies: ``.boxed_type``,
|
||||
``.src_uid``, ``.ipc_msg`` and the fancy ``.pformat()`` tb-box
|
||||
rendering.
|
||||
|
||||
Practical reading guide: a *sender-side* MTE (``Started``,
|
||||
``Return``) points straight at your offending ``await
|
||||
ctx.started()`` or ``return`` statement, while a *receiver-side*
|
||||
MTE (``Yield``) surfaces from the consumer's ``receive()`` call
|
||||
with the relay copy delivered back to the producer. Either way
|
||||
the failure is scoped to that one dialog; sibling contexts on the
|
||||
same channel keep right on trucking.
|
||||
|
||||
Custom wire types: ``mk_codec()`` and friends
|
||||
---------------------------------------------
|
||||
msgspec covers a wide set of `builtin types`__ natively; for
|
||||
anything else you teach the codec via extension hooks. The
|
||||
easiest path is per-endpoint: ``@tractor.context()`` accepts
|
||||
``enc_hook``/``dec_hook`` params right alongside ``pld_spec``.
|
||||
For full control build and apply a codec yourself; encode-side:
|
||||
|
||||
__ https://jcristharif.com/msgspec/supported-types.html
|
||||
|
||||
.. code:: python
|
||||
|
||||
from tractor.msg import mk_codec, apply_codec
|
||||
|
||||
codec = mk_codec(
|
||||
enc_hook=nsp_to_str, # your-type -> wire-type
|
||||
ext_types=[NamespacePath],
|
||||
)
|
||||
with apply_codec(codec): # ContextVar-scoped override
|
||||
... # msgs sent by this task now encode NSPs
|
||||
|
||||
and decode-side, scoped to an open context (note the import from
|
||||
``tractor.msg._ops``, not yet re-exported):
|
||||
|
||||
.. code:: python
|
||||
|
||||
from tractor.msg._ops import limit_plds
|
||||
|
||||
with limit_plds(
|
||||
NamespacePath,
|
||||
dec_hook=str_to_nsp, # wire-type -> your-type
|
||||
ext_types=[NamespacePath],
|
||||
):
|
||||
... # this dialog's payloads decode as NSPs
|
||||
|
||||
``apply_codec()`` is ``ContextVar``-scoped: it overrides the
|
||||
codec for the current task (and only that task), not the whole
|
||||
process. For complete working flows, including hook pairing rules
|
||||
and roundtrip cases, see ``tests/msg/test_ext_types_msgspec.py``
|
||||
and ``tests/msg/test_pldrx_limiting.py``.
|
||||
|
||||
The runtime dogfoods this pattern with
|
||||
:class:`tractor.msg.NamespacePath`: a ``str``-subtype shaped like
|
||||
``'module.path:obj_name'`` used for every RPC target reference.
|
||||
It ships over the wire as a plain string yet ``.load_ref()``-s
|
||||
back to the actual object in the receiving actor's memory domain;
|
||||
a minimal "pointer type" for shared-nothing systems.
|
||||
|
||||
Toward capability-based msging
|
||||
------------------------------
|
||||
The ``pld_spec`` + codec-hook layer is the foundation for the
|
||||
long-game: **capability-based msging** where each dialog's
|
||||
type contract doubles as a capability grant, negotiated as part
|
||||
of the protocol itself. That work is tracked in `#196`_ (with the
|
||||
original typed-proto epic in `#36`_); if strongly-typed
|
||||
distributed systems get you going, we'd love your input.
|
||||
|
||||
Where to next?
|
||||
--------------
|
||||
.. seealso::
|
||||
|
||||
- :doc:`/guide/context` for the dialog API these msgs
|
||||
implement: ``started()``, streams and results.
|
||||
- :doc:`/guide/asyncio` for shuttling (typed) payloads into
|
||||
``asyncio``-land via an infected subactor.
|
||||
- the msgspec_ docs for everything your payload types can be.
|
||||
|
||||
.. _structured concurrency: https://en.wikipedia.org/wiki/Structured_concurrency
|
||||
.. _msgspec: https://jcristharif.com/msgspec/
|
||||
.. _cheap or nasty: https://zguide.zeromq.org/docs/chapter7/#The-Cheap-or-Nasty-Pattern
|
||||
.. _(un)protocol: https://zguide.zeromq.org/docs/chapter7/#Unprotocols
|
||||
.. _#196: https://github.com/goodboy/tractor/issues/196
|
||||
.. _#36: https://github.com/goodboy/tractor/issues/36
|
||||
|
|
@ -0,0 +1,176 @@
|
|||
Parallelism and worker pools
|
||||
============================
|
||||
|
||||
The initial ask is almost always the same: *"how do i make a worker
|
||||
pool?"* — i.e. the thing :mod:`multiprocessing` and
|
||||
:class:`concurrent.futures.ProcessPoolExecutor` get reached for
|
||||
once the GIL becomes the enemy.
|
||||
|
||||
Here's the structured concurrency (SC) answer: ``tractor`` is built
|
||||
to handle any SC process tree you can imagine; a "worker pool"
|
||||
pattern is a trivial special case. So instead of shipping a pool
|
||||
*class* with knobs bolted on, you compose one from the same two
|
||||
ingredients used everywhere else in ``tractor``: an actor nursery
|
||||
and some IPC.
|
||||
|
||||
The stdlib baseline
|
||||
-------------------
|
||||
|
||||
For a fair comparison, start from the canonical
|
||||
:class:`~concurrent.futures.ProcessPoolExecutor` primes example
|
||||
straight out of the Python docs,
|
||||
|
||||
.. literalinclude:: ../../examples/parallelism/concurrent_futures_primes.py
|
||||
:caption: examples/parallelism/concurrent_futures_primes.py
|
||||
:language: python
|
||||
|
||||
Synchronous code, a hidden thread + IPC machine under the hood, and
|
||||
an API surface (executors, futures, ``.map()``) invented to paper
|
||||
over the fact that the pool isn't part of your program's task tree.
|
||||
Keep an eye on three things for the rewrite: how work is submitted,
|
||||
how results come back, and what happens when a worker dies.
|
||||
|
||||
The ``tractor`` way
|
||||
-------------------
|
||||
|
||||
Now the same workload as a ``tractor`` program,
|
||||
|
||||
.. literalinclude:: ../../examples/parallelism/concurrent_actors_primes.py
|
||||
:caption: examples/parallelism/concurrent_actors_primes.py
|
||||
:language: python
|
||||
|
||||
What's different (and what isn't),
|
||||
|
||||
- ``worker_pool()`` is ~30 lines of *your* code: an actor nursery
|
||||
spawning ``workers`` subactors — each a full process running its
|
||||
own ``trio`` task tree — kept alive and ready for work until the
|
||||
block exits; ``enable_modules=[__name__]`` is the capability
|
||||
allowlist letting them run this module's functions,
|
||||
- jobs are "submitted" by just... calling the function:
|
||||
``portal.run(is_prime, n=value)`` runs ``is_prime()`` in a
|
||||
worker and hands back its result like any local ``await``,
|
||||
- results stream back through a plain
|
||||
:func:`trio.open_memory_channel` *as they complete* — no futures
|
||||
and no polling,
|
||||
- teardown is one ``await tn.cancel()``
|
||||
(:meth:`tractor.ActorNursery.cancel`), and any worker crash
|
||||
triggers the one-cancels-all machinery from
|
||||
:doc:`/guide/cancellation` — a dead worker can never strand the
|
||||
pool.
|
||||
|
||||
This uses no extra threads, fancy semaphores or futures; all we
|
||||
need is ``tractor``'s IPC! The full scorecard,
|
||||
|
||||
.. list-table::
|
||||
:header-rows: 1
|
||||
:widths: 50 50
|
||||
|
||||
* - ``concurrent.futures``
|
||||
- ``tractor``
|
||||
* - ``ProcessPoolExecutor()``
|
||||
- ``worker_pool()`` — yours, ~30 lines
|
||||
* - ``executor.map(is_prime, PRIMES)``
|
||||
- ``actor_map(is_prime, PRIMES)`` async-gen
|
||||
* - ``Future`` + internal result queue
|
||||
- :func:`trio.open_memory_channel`
|
||||
* - results in input order
|
||||
- results as they complete
|
||||
* - worker crash -> ``BrokenProcessPool``
|
||||
- boxed :class:`tractor.RemoteActorError`
|
||||
* - pool teardown on ``with`` exit
|
||||
- one-cancels-all nursery teardown
|
||||
|
||||
.. margin:: How many workers?
|
||||
|
||||
Same calculus as any process pool: about core-count for
|
||||
CPU-bound work (the default sizing in
|
||||
:doc:`/guide/clustering`); more only if workers block on I/O —
|
||||
though at that point you likely want plain ``trio`` tasks, not
|
||||
processes.
|
||||
|
||||
And because the pool is just SC code, every variation — bounded
|
||||
submission, per-worker state, streaming partial results (see
|
||||
:doc:`/guide/streaming`), nested pools — is a local edit to your
|
||||
pool, not a feature request against an executor class B)
|
||||
|
||||
An *async* pool, though?
|
||||
************************
|
||||
|
||||
Yep: RPC targets must be async functions — the runtime rejects a
|
||||
plain ``def`` with ``TypeError: ... must be an async function!``.
|
||||
That's not zealotry, it's cancel-responsiveness: each worker is a
|
||||
full ``trio`` runtime whose msg loop is what hears graceful cancel
|
||||
requests, and a hot loop that never yields can't be (politely)
|
||||
interrupted.
|
||||
|
||||
Two practical consequences,
|
||||
|
||||
- CPU-bound loops should checkpoint once in a while; note how
|
||||
``burn_cpu()`` in the next example sprinkles ``await
|
||||
trio.sleep()`` calls so the worker stays responsive while still
|
||||
pegging a core,
|
||||
- if some sync call blocks a worker anyway you're still covered:
|
||||
an unresponsive actor just rides the graceful-then-hard teardown
|
||||
ladder from :doc:`/guide/cancellation` instead of acking its
|
||||
cancel — slower, but never a zombie.
|
||||
|
||||
Run a func in a process
|
||||
-----------------------
|
||||
|
||||
Even a pool can be overkill; "run this one async func in a
|
||||
subprocess and give me the result" is a one-liner via
|
||||
:meth:`tractor.ActorNursery.run_in_actor`,
|
||||
|
||||
.. literalinclude:: ../../examples/parallelism/single_func.py
|
||||
:caption: examples/parallelism/single_func.py
|
||||
:language: python
|
||||
|
||||
``run_in_actor()`` is a *convenience wrapper* — spawn an actor, run
|
||||
exactly one task in it, reap on result — not the core spawning
|
||||
model (that's :meth:`tractor.ActorNursery.start_actor` plus
|
||||
:meth:`tractor.Portal.open_context`; see :doc:`/guide/context`).
|
||||
But for this fire-and-collect shape it's exactly the right amount
|
||||
of typing.
|
||||
|
||||
As the module docstring suggests, run it under a process-tree
|
||||
monitor to watch the child appear and get reaped,
|
||||
|
||||
.. code:: bash
|
||||
|
||||
$TERM -e watch -n 0.1 "pstree -a $$" \
|
||||
& python examples/parallelism/single_func.py \
|
||||
&& kill $!
|
||||
|
||||
You'll see a core get burned in both parent and child — real
|
||||
parallelism, no GIL sharing, since these are processes (i.e.
|
||||
*non-shared-memory threads*).
|
||||
|
||||
When all you have is sync code
|
||||
------------------------------
|
||||
|
||||
Honesty corner: if your workload is purely *synchronous* functions
|
||||
and you've zero need for IPC dialogs, streaming, daemons or
|
||||
supervision trees — i.e. you really do just want
|
||||
"``ProcessPoolExecutor`` but ``trio``-native" — the smaller,
|
||||
focused `trio-parallel`_ project may serve you better. ``tractor``
|
||||
happily covers the use case (as above) but brings a whole runtime
|
||||
along for the ride. (And when blocking I/O — not the GIL — is the
|
||||
actual problem, plain in-process :func:`trio.to_thread.run_sync`
|
||||
may be all you ever needed.)
|
||||
|
||||
And to *see* that runtime's process-management story — a per-core
|
||||
fleet self-destructing with zero zombies left behind — go run
|
||||
``examples/parallelism/we_are_processes.py``, walked through in
|
||||
the :doc:`/start/quickstart`.
|
||||
|
||||
.. seealso::
|
||||
|
||||
- :doc:`/guide/clustering` — the one-liner flat-cluster
|
||||
convenience (``open_actor_cluster()``) for when even a
|
||||
hand-rolled pool is too much typing,
|
||||
- :doc:`/guide/cancellation` — why pool teardown is bulletproof
|
||||
(graceful-then-hard escalation, no zombies),
|
||||
- :doc:`/guide/context` — the core per-task API your pool
|
||||
workers can graduate to.
|
||||
|
||||
.. _trio-parallel: https://github.com/richardsheridan/trio-parallel
|
||||
|
|
@ -0,0 +1,177 @@
|
|||
RPC: calling into other actors
|
||||
==============================
|
||||
Every spawn call from :doc:`/guide/spawning` hands you back
|
||||
a :class:`~tractor.Portal`: a live handle for calling into
|
||||
another actor's **memory domain**. The name is borrowed from
|
||||
``trio``'s portal concept — an object you use to submit work
|
||||
*into* a separate concurrency domain — except here that domain
|
||||
is a whole other process.
|
||||
|
||||
.. d2:: diagrams/runtime_stack.d2
|
||||
:margin:
|
||||
:caption: The layers a ``portal.run()`` request rides through.
|
||||
:alt: app, tractor runtime, IPC channel and OS process layers
|
||||
|
||||
There are **no proxy objects** and no special calling
|
||||
conventions: you pass a plain function reference plus keyword
|
||||
args, and Python's normal ``await``-able semantics apply. The
|
||||
function just happens to *run somewhere else*; from the calling
|
||||
task it looks as though it was called locally. And since this is
|
||||
all structured concurrency (SC) under the hood, the remote task
|
||||
runs inside the callee's supervised task tree while its result
|
||||
— or its failure, as a boxed
|
||||
:exc:`~tractor.RemoteActorError` — always comes back to *you*.
|
||||
|
||||
``Portal.run()``: pass the function, not a string
|
||||
-------------------------------------------------
|
||||
:meth:`~tractor.Portal.run` schedules an async function as
|
||||
a **new task** in the remote actor and waits on its result:
|
||||
|
||||
.. code:: python
|
||||
|
||||
async with tractor.open_nursery() as an:
|
||||
portal = await an.start_actor(
|
||||
'service',
|
||||
enable_modules=[__name__],
|
||||
)
|
||||
answer = await portal.run(movie_theatre_question)
|
||||
|
||||
The rules of engagement:
|
||||
|
||||
- the target must be an **async function** and its defining
|
||||
module must be in the callee's ``enable_modules`` allowlist,
|
||||
else an :exc:`~tractor.ModuleNotExposed` error is relayed
|
||||
back (see :doc:`/guide/spawning` for the capability-allowlist
|
||||
story).
|
||||
- arguments are passed **by keyword only**; they ride the IPC
|
||||
layer as msgspec_-encoded msgs, so keep them serializable.
|
||||
- every call schedules a *fresh* task remotely — call it twice
|
||||
and the callee runs two tasks, each supervised in its own
|
||||
right.
|
||||
- remote exceptions re-raise locally as
|
||||
:exc:`~tractor.RemoteActorError` with the original type
|
||||
preserved via ``.boxed_type``.
|
||||
|
||||
.. note::
|
||||
|
||||
Passing dotted-path *strings* to ``run()`` is an ancient,
|
||||
deprecated form; always pass the function reference. If you
|
||||
really need name-based addressing use ``run_from_ns()``
|
||||
below.
|
||||
|
||||
Namespaced daemons: ``run_from_ns()``
|
||||
-------------------------------------
|
||||
Sometimes the calling process can't (or shouldn't) import the
|
||||
target function — think a long-running rpc-daemon serving
|
||||
modules your client never loads. For that,
|
||||
:meth:`~tractor.Portal.run_from_ns` takes the explicit
|
||||
namespace path:
|
||||
|
||||
.. code:: python
|
||||
|
||||
await portal.run_from_ns('mypkg.service', 'ping')
|
||||
|
||||
This is literally how ``.run()`` works underneath: the pair is
|
||||
encoded as a ``'mod.path:func'`` style msg and resolved against
|
||||
the callee's enabled modules.
|
||||
|
||||
One special namespace exists: ``'self'`` resolves to the remote
|
||||
:class:`~tractor.Actor` instance, i.e. the runtime itself. It's
|
||||
how internal machinery (cancel requests, registry ops) travels;
|
||||
don't build your app on it.
|
||||
|
||||
One-shot results: ``wait_for_result()``
|
||||
---------------------------------------
|
||||
A portal returned from
|
||||
:meth:`~tractor.ActorNursery.run_in_actor` has exactly one
|
||||
"main" task running remotely; that task's ``return`` value is
|
||||
delivered as the portal's *final result*:
|
||||
|
||||
.. code:: python
|
||||
|
||||
portal = await an.run_in_actor(fib, n=10)
|
||||
final = await portal.wait_for_result()
|
||||
|
||||
Semantics worth knowing:
|
||||
|
||||
- it blocks until the remote task returns, re-raising any
|
||||
remote error in the usual boxed form.
|
||||
- once resolved it's idempotent: later calls return the same
|
||||
cached value.
|
||||
- a *daemon* portal (from ``start_actor()``) has no main task,
|
||||
so there's no final result to wait for: you'll get a warning
|
||||
plus a ``NoResult`` sentinel. Results of individual daemon
|
||||
calls come straight back from each ``await portal.run()``.
|
||||
|
||||
Pure RPC daemons: ``run_daemon()``
|
||||
----------------------------------
|
||||
When a process's *only* job is to sit at the root of its own
|
||||
tree and serve RPC, skip the boilerplate with
|
||||
:func:`tractor.run_daemon`:
|
||||
|
||||
.. code:: python
|
||||
|
||||
import tractor
|
||||
|
||||
tractor.run_daemon(
|
||||
['mypkg.service'],
|
||||
name='service',
|
||||
)
|
||||
|
||||
It's a blocking convenience (it calls ``trio.run()`` for you):
|
||||
boot a root actor with the given modules enabled for RPC, then
|
||||
sleep until cancelled. Pair it with the discovery system —
|
||||
:func:`tractor.find_actor` / :func:`tractor.wait_for_actor`
|
||||
from a *separate* program — and you've got a tiny service
|
||||
architecture with zero framework ceremony; see
|
||||
``examples/service_daemon_discovery.py`` for the full pattern.
|
||||
|
||||
Fan-out: RPC through nested trees
|
||||
---------------------------------
|
||||
Portals compose. An RPC task is just a ``trio`` task, so it can
|
||||
open its own :class:`~tractor.ActorNursery` and portal into
|
||||
*its* children — one inbound call fanning out into a whole
|
||||
sub-tree of work. The mid-tier function from the nested-tree
|
||||
example:
|
||||
|
||||
.. literalinclude:: ../../examples/nested_actor_tree.py
|
||||
:caption: examples/nested_actor_tree.py (supervisor fan-out)
|
||||
:language: python
|
||||
:pyobject: fan_out_squares
|
||||
|
||||
The root portals into the ``supervisor`` actor; the
|
||||
supervisor's RPC task spawns the leaf workers, portals into
|
||||
each, and returns the combined result back up. Failures at any
|
||||
depth relay hop-by-hop as boxed errors, and cancelling the root
|
||||
call tears down the entire sub-tree — SC, transitively.
|
||||
|
||||
When to graduate to ``Context``
|
||||
-------------------------------
|
||||
``portal.run()`` is great for one-shot, request-response calls.
|
||||
Reach for :meth:`~tractor.Portal.open_context` with an
|
||||
``@tractor.context`` endpoint as soon as you want:
|
||||
|
||||
- a long-lived dialog with state held on both sides,
|
||||
- bidirectional streaming via ``ctx.open_stream()``,
|
||||
- typed payload contracts (``pld_spec``) enforced at the msg
|
||||
layer,
|
||||
- or *task-scoped* cancellation: ``Context.cancel()`` cancels
|
||||
just the linked remote task, whereas
|
||||
:meth:`~tractor.Portal.cancel_actor` nukes the **entire**
|
||||
remote runtime and its process.
|
||||
|
||||
In fact the source plans for ``Portal.run()`` itself to be
|
||||
rebuilt on top of ``open_context()`` — contexts *are* the core
|
||||
inter-actor protocol. Take the full tour in
|
||||
:doc:`/guide/context`.
|
||||
|
||||
.. seealso::
|
||||
|
||||
- :doc:`/guide/spawning` — where portals come from and how
|
||||
their actors are supervised.
|
||||
- :doc:`/guide/context` — the structured cross-actor task
|
||||
API: handshake, streaming, typed payloads.
|
||||
- :doc:`/guide/cancellation` — what happens to in-flight RPC
|
||||
when trees get torn down.
|
||||
|
||||
.. _msgspec: https://jcristharif.com/msgspec/
|
||||
|
|
@ -0,0 +1,299 @@
|
|||
Spawning actors
|
||||
===============
|
||||
If you know trio_ you know the drill: you don't get to launch
|
||||
a task off into the void, you open a nursery_, the nursery owns
|
||||
the task, and the block can't exit until every child is done.
|
||||
That discipline is `structured concurrency`_ (SC) — see the
|
||||
seminal `blog post`_ if you haven't yet — and it's the whole
|
||||
religion around here.
|
||||
|
||||
``tractor`` applies that exact discipline to **processes**: an
|
||||
:class:`~tractor.ActorNursery` is a *process nursery*. Every
|
||||
"task" it starts is a fresh Python process running its own
|
||||
``trio.run()``-scheduled task tree; we call each one a
|
||||
``trio``-"*actor*". Parents must wait on (and clean up after)
|
||||
their children, transitively, all the way down the tree.
|
||||
|
||||
.. d2:: diagrams/actor_tree.d2
|
||||
:caption: A process tree of ``trio``-task-trees.
|
||||
:alt: a nested actor tree where every parent supervises its children
|
||||
|
||||
Though a "process nursery" differs in complexity (and slightly
|
||||
in semantics) from a single-threaded task nursery, most of the
|
||||
interface is the same. The main difference is that each spawned
|
||||
child contains a full, *parallel-executing* ``trio`` task tree.
|
||||
The following super powers ensue:
|
||||
|
||||
- tasks started in a child actor are completely independent of
|
||||
tasks started in the current process; they execute in
|
||||
**parallel** and are scheduled by their own actor's ``trio``
|
||||
run loop.
|
||||
- tasks scheduled in a remote process still maintain an SC
|
||||
protocol *across memory boundaries* using a so called
|
||||
"SC dialogue protocol" which keeps task-hierarchy lifetimes
|
||||
linked across the IPC layer.
|
||||
- a remote task can fail and have that failure relayed back to
|
||||
the caller task (living in some other actor) as a serialized
|
||||
:exc:`~tractor.RemoteActorError`; no spawned process or RPC
|
||||
task can ever just go off on its own.
|
||||
|
||||
Opening a (process) nursery
|
||||
---------------------------
|
||||
:func:`tractor.open_nursery` is the entrypoint:
|
||||
|
||||
.. code:: python
|
||||
|
||||
async def main():
|
||||
async with tractor.open_nursery() as an:
|
||||
... # spawn some actors B)
|
||||
|
||||
trio.run(main)
|
||||
|
||||
Notice there's no runtime-boot ceremony: if no actor runtime is
|
||||
up yet (i.e. you're in a plain old Python process),
|
||||
``open_nursery()`` *implicitly* enters
|
||||
:func:`tractor.open_root_actor` for you, making this process the
|
||||
**root actor** of a new tree. Any extra keyword args you pass
|
||||
are proxied straight through to ``open_root_actor()``, so the
|
||||
runtime config lives wherever you open your first nursery:
|
||||
|
||||
.. code:: python
|
||||
|
||||
async with tractor.open_nursery(
|
||||
loglevel='info',
|
||||
debug_mode=True, # crash-to-REPL for the whole tree
|
||||
) as an:
|
||||
...
|
||||
|
||||
If you want the runtime up *without* spawning anything (or you
|
||||
prefer the config to be loudly explicit) enter
|
||||
``open_root_actor()`` yourself first; the nursery will detect
|
||||
the running runtime and skip the implicit boot. Either way,
|
||||
nesting a second root inside an existing tree is an error.
|
||||
|
||||
Inside a *subactor* the same call just works: any actor may open
|
||||
nurseries of its own, which is how you get arbitrarily deep
|
||||
trees (more on that below).
|
||||
|
||||
``start_actor()``: daemons that live until cancelled
|
||||
----------------------------------------------------
|
||||
:meth:`~tractor.ActorNursery.start_actor` is **the** core
|
||||
spawning primitive. It starts a *daemon* actor: a process with
|
||||
no designated "main task" besides the runtime itself. It boots,
|
||||
registers with its parent, and then sits there serving RPC
|
||||
requests until somebody cancels it. You get back a
|
||||
:class:`~tractor.Portal` for doing exactly that kind of
|
||||
somebody-ing:
|
||||
|
||||
.. literalinclude:: ../../examples/actor_spawning_and_causality_with_daemon.py
|
||||
:caption: examples/actor_spawning_and_causality_with_daemon.py
|
||||
:language: python
|
||||
|
||||
What's going on here?
|
||||
|
||||
- ``start_actor('frank', enable_modules=[__name__])`` forks off
|
||||
a new process, boots a ``tractor`` runtime inside it, and
|
||||
allows it to serve functions from the current module (see the
|
||||
allowlist section below).
|
||||
- each ``await portal.run(...)`` schedules a *new* task in
|
||||
frank's task tree and waits on its result — the full RPC story
|
||||
lives in :doc:`/guide/rpc`.
|
||||
- frank has no main task to complete, so without the final
|
||||
``await portal.cancel_actor()`` the nursery block would wait
|
||||
on him **forever**. Daemon lifetimes are *yours* to end; that
|
||||
explicitness is the point.
|
||||
|
||||
``run_in_actor()``: quick one-shot parallelism
|
||||
----------------------------------------------
|
||||
:meth:`~tractor.ActorNursery.run_in_actor` is the convenience
|
||||
wrapper: spawn an actor, run exactly one async function in it,
|
||||
then reap the process as soon as the result arrives.
|
||||
|
||||
.. code:: python
|
||||
|
||||
async with tractor.open_nursery() as an:
|
||||
portal = await an.run_in_actor(burn_cpu)
|
||||
# burn rubber in the parent too...
|
||||
await burn_cpu()
|
||||
total = await portal.wait_for_result()
|
||||
|
||||
A few details worth knowing:
|
||||
|
||||
- the actor is named after the function unless you pass
|
||||
``name='something_cuter'``.
|
||||
- the function's module is auto-added to the child's
|
||||
``enable_modules`` allowlist.
|
||||
- extra ``**kwargs`` are forwarded to the function itself.
|
||||
- the child is *auto-cancelled* once its "main" result lands;
|
||||
at nursery exit these run-once children are always reaped
|
||||
first (causality_ is paramount!).
|
||||
|
||||
.. note::
|
||||
|
||||
``run_in_actor()`` is a convenience, **not** the core model.
|
||||
The source literally marks it for an eventual rebuild as
|
||||
a thin "hilevel" wrapper on top of
|
||||
:meth:`~tractor.Portal.open_context` (the modern inter-actor
|
||||
task API). Teach your fingers to use it for quick
|
||||
fire-and-collect parallelism — think a per-function
|
||||
trio-parallel_ style one-shot — and reach for
|
||||
``start_actor()`` + ``open_context()`` for anything
|
||||
long-lived, stateful or streaming
|
||||
(:doc:`/guide/context`).
|
||||
|
||||
Actor lifetimes and teardown order
|
||||
----------------------------------
|
||||
So we have two lifetime flavors:
|
||||
|
||||
- **run-once** (``run_in_actor()``): lives exactly as long as
|
||||
its single task; reaped the moment its result (or error)
|
||||
arrives.
|
||||
- **daemon** (``start_actor()``): lives until *someone* cancels
|
||||
it — an explicit ``await portal.cancel_actor()``, a bulk
|
||||
``await an.cancel()``, or the one-cancels-all strategy kicking
|
||||
in on error.
|
||||
|
||||
On a clean exit of the nursery block the teardown order is:
|
||||
|
||||
1. the nursery waits on every run-once actor's final result;
|
||||
any errors from these are raised immediately so your code
|
||||
(acting as supervisor) gets first crack at handling them.
|
||||
2. then it waits on daemon actors — **indefinitely**. If you
|
||||
spawned a daemon, you own its lifetime.
|
||||
|
||||
When a child *is* cancelled, teardown is graceful-first per SC
|
||||
discipline: the runtime sends an IPC cancel request and gives
|
||||
the child a bounded window to ack; only when a child is too
|
||||
slow does the nursery escalate to an OS-level hard kill of the
|
||||
process. There is no path where a child is silently left
|
||||
running:
|
||||
|
||||
``tractor`` tries to protect you from zombies, no matter
|
||||
what. If you can create zombie child processes (without
|
||||
using a system signal) it **is a bug**.
|
||||
|
||||
Per-process cleanup hooks
|
||||
*************************
|
||||
Need something torn down when an actor's runtime exits, no
|
||||
matter how it exits? Every actor carries
|
||||
a process-global :class:`contextlib.ExitStack` at
|
||||
``Actor.lifetime_stack`` which is closed at the very end of
|
||||
runtime teardown:
|
||||
|
||||
.. code:: python
|
||||
|
||||
db = await connect_db()
|
||||
tractor.current_actor().lifetime_stack.callback(db.close)
|
||||
|
||||
(A so-far under-advertised api — expect it to get more love.)
|
||||
|
||||
When things blow up: one-cancels-all
|
||||
------------------------------------
|
||||
The default (and currently only) supervision strategy is the
|
||||
same one ``trio`` nurseries use: **one-cancels-all**. If your
|
||||
nursery-block body errors, every child actor is cancelled. If
|
||||
a child errors, the failure is relayed to the nursery as a
|
||||
boxed :exc:`~tractor.RemoteActorError` (original type preserved
|
||||
via ``.boxed_type``), all *other* children are cancelled, and
|
||||
the error(s) re-raise locally — exactly like ``trio``, just
|
||||
process-wide. Erlang-style alternative strategies are a long
|
||||
standing roadmap item.
|
||||
|
||||
The full story — how cancel requests relay across the tree, who
|
||||
``.canceller`` was, debugging mid-teardown — lives in
|
||||
:doc:`/guide/cancellation`.
|
||||
|
||||
The module allowlist: ``enable_modules``
|
||||
----------------------------------------
|
||||
A subactor will only serve functions from modules its parent
|
||||
*explicitly* enabled at spawn time:
|
||||
|
||||
.. code:: python
|
||||
|
||||
portal = await an.start_actor(
|
||||
'service',
|
||||
enable_modules=['mypkg.service'], # or [__name__]
|
||||
)
|
||||
|
||||
At child boot the runtime imports each listed module so inbound
|
||||
RPC requests can resolve function references against it. Ask
|
||||
a peer to run something from any *other* module and you get an
|
||||
:exc:`~tractor.ModuleNotExposed` error relayed back — the child
|
||||
never even looks the function up.
|
||||
|
||||
Think of it as the first, deliberately coarse layer of
|
||||
capability-style permissioning: if you don't hand an actor
|
||||
a module, no peer can invoke anything inside it. (Finer-grained
|
||||
capability-based messaging protocols are on the roadmap.)
|
||||
|
||||
The ``enable_modules=[__name__]`` idiom — "let the child run
|
||||
functions from the *current* module" — is what you'll use in
|
||||
most scripts; bigger apps tend to pass dedicated service-module
|
||||
paths instead.
|
||||
|
||||
Per-child knobs
|
||||
---------------
|
||||
Both spawn methods accept per-child config so one weird child
|
||||
doesn't have to drag the whole tree along:
|
||||
|
||||
- ``loglevel='cancel'`` — crank console logging for just this
|
||||
subactor (the ``TRACTOR_LOGLEVEL`` env var overrides whatever
|
||||
the *root* was passed, handy for test runs).
|
||||
- ``debug_mode=True`` — arm the crash-handling REPL machinery
|
||||
for just this child instead of tree-wide, i.e. the selective
|
||||
flavor of ``open_nursery(debug_mode=True)``; see
|
||||
:doc:`/guide/debugging` for the multi-process debugger tour.
|
||||
- ``infect_asyncio=True`` — run the child with ``trio`` as an
|
||||
``asyncio`` guest, aka "infected asyncio" mode.
|
||||
- ``enable_transports=['uds']`` — pick the IPC transport this
|
||||
child should listen on (default ``'tcp'``).
|
||||
|
||||
Trees all the way down
|
||||
----------------------
|
||||
Since any actor can open an ``ActorNursery``, supervision trees
|
||||
compose to arbitrary depth: a subactor can be a supervisor of
|
||||
*its own* subactors, with every level holding the same SC
|
||||
guarantees — error relay up, cancellation down, no orphans.
|
||||
|
||||
.. literalinclude:: ../../examples/nested_actor_tree.py
|
||||
:caption: examples/nested_actor_tree.py
|
||||
:language: python
|
||||
|
||||
Here the root spawns a ``supervisor`` actor whose RPC task opens
|
||||
its *own* nursery and spawns the leaf workers; one call from the
|
||||
root fans out through the middle layer and the aggregate comes
|
||||
back up. Teardown ripples in reverse: the leaves are reaped when
|
||||
the supervisor's nursery exits, the supervisor when the root
|
||||
cancels it.
|
||||
|
||||
Watching your tree grow
|
||||
-----------------------
|
||||
Actors are real processes, so your favorite system tools just
|
||||
work. The house incantation runs any example beside a live
|
||||
process-tree monitor::
|
||||
|
||||
$TERM -e watch -n 0.1 "pstree -a $$" \
|
||||
& python examples/nested_actor_tree.py \
|
||||
&& kill $!
|
||||
|
||||
Every subactor also sets its OS process title to a stable
|
||||
``_subactor[<name>@<uuid-prefix>]`` marker, so ``htop``,
|
||||
``ps`` and friends show *which actor is which* at a glance::
|
||||
|
||||
pgrep -af '_subactor\['
|
||||
|
||||
.. seealso::
|
||||
|
||||
- :doc:`/guide/rpc` — actually invoking functions through
|
||||
all these portals you've been collecting.
|
||||
- :doc:`/guide/context` — the structured, streaming-capable
|
||||
inter-actor task API.
|
||||
- :doc:`/guide/cancellation` — cross-actor cancellation and
|
||||
error propagation semantics in depth.
|
||||
|
||||
.. _trio: https://github.com/python-trio/trio
|
||||
.. _nursery: https://trio.readthedocs.io/en/latest/reference-core.html#nurseries-and-spawning
|
||||
.. _structured concurrency: https://en.wikipedia.org/wiki/Structured_concurrency
|
||||
.. _blog post: https://vorpus.org/blog/notes-on-structured-concurrency-or-go-statement-considered-harmful/
|
||||
.. _causality: https://vorpus.org/blog/some-thoughts-on-asynchronous-api-design-in-a-post-asyncawait-world/#c-c-c-c-causality-breaker
|
||||
.. _trio-parallel: https://github.com/richardsheridan/trio-parallel
|
||||
|
|
@ -0,0 +1,244 @@
|
|||
Cross-process streaming
|
||||
=======================
|
||||
|
||||
Spawning processes is the boring half of ``tractor``: the **real
|
||||
cool stuff** is the native support for cross-process *streaming*.
|
||||
Yes, you saw it here first — 2-way msg streams with reliable,
|
||||
transitive setup/teardown semantics, wired straight into the
|
||||
runtime's `structured concurrency`_ (SC) supervision machinery so
|
||||
that *how* a stream ends is part of the protocol.
|
||||
|
||||
No broker, no topic exchange, no IDL compiler. The IPC layer is a
|
||||
deliberately "`cheap or nasty`_" `(un)protocol`_: a tiny set of
|
||||
msgspec_-typed msgs over a transport (TCP or UDS today) with
|
||||
payload typing opt-in per dialog — handshake msgs get the *nasty*
|
||||
treatment (strict validation) while high-rate stream payloads
|
||||
stay *cheap* (receiver-side checks only). See
|
||||
:doc:`/guide/context` for the typed ``pld_spec`` contract bits.
|
||||
|
||||
Two ways to stream
|
||||
------------------
|
||||
|
||||
.. margin:: It's a ``trio.abc.Channel``
|
||||
|
||||
:class:`tractor.MsgStream` implements
|
||||
:class:`trio.abc.Channel` — ``send()``,
|
||||
``receive()``, async-iteration, ``aclose()`` —
|
||||
so trio-generic channel code drives an IPC
|
||||
stream unchanged.
|
||||
|
||||
- **Bidirectional, context-based**: open a
|
||||
:class:`tractor.Context` to a peer task then enter
|
||||
``ctx.open_stream()`` for a full-duplex
|
||||
:class:`tractor.MsgStream`. This is the modern core API, taught
|
||||
end-to-end in :doc:`/guide/context`; we won't re-teach it here.
|
||||
|
||||
- **One-way, portal-based**: point
|
||||
:meth:`tractor.Portal.open_stream_from` at a plain async
|
||||
generator fn in the peer actor. Legacy, but perfectly fine for
|
||||
simple produce/consume pipelines — and it powers the classic
|
||||
examples below.
|
||||
|
||||
Rule of thumb: if the consumer ever needs to *talk back* — acks,
|
||||
control msgs, a final result — use a context. If it's a pure
|
||||
pipeline stage, either works and the one-way form is less typing.
|
||||
|
||||
One-way streaming from an async generator
|
||||
-----------------------------------------
|
||||
|
||||
The OG api. Write an async generator in the target actor's
|
||||
module; iterate its yields from the spawning side:
|
||||
|
||||
.. literalinclude:: ../../examples/asynchronous_generators.py
|
||||
:caption: examples/asynchronous_generators.py
|
||||
:language: python
|
||||
|
||||
Each ``yield`` crosses the process boundary as one msg and feeds
|
||||
the parent's ``async for``. When the consumer ``break``\ s out
|
||||
and exits the ``open_stream_from()`` block the far-end generator
|
||||
task is cancelled for you: the producer's lifetime is *coupled to
|
||||
the consumer's scope* so a one-way stream can never leak a remote
|
||||
task.
|
||||
|
||||
Any extra kwargs (``stream_data, seed=100`` style) are forwarded
|
||||
to the remote generator's call, and a non-async-gen target is
|
||||
rejected up front with a ``TypeError``.
|
||||
|
||||
.. note::
|
||||
|
||||
No decorator required — any plain async-gen fn works. You may
|
||||
still meet ``@tractor.stream`` in the wild; it's the legacy
|
||||
marker for one-way endpoints and sticks around only for
|
||||
compat (heads up: the param name ``ctx`` is reserved for
|
||||
``@context`` endpoints nowadays, so legacy fns should call
|
||||
theirs ``stream``). New code wanting anything fancier than a
|
||||
one-way pipe should use :func:`tractor.context` +
|
||||
``ctx.open_stream()``.
|
||||
|
||||
.. warning::
|
||||
|
||||
One-way means one way: there's no sending *to* the generator
|
||||
side and no graceful consumer-to-producer stop msg — the
|
||||
teardown above is cancel-based. Needing upstream control flow
|
||||
is the sign you've outgrown this API.
|
||||
|
||||
A full-fledged streaming service
|
||||
--------------------------------
|
||||
|
||||
Now let's get fancy: compose one-way streams through a nested
|
||||
actor tree and you've got yourself a fan-in pipeline.
|
||||
|
||||
.. d2:: diagrams/streaming_pipeline.d2
|
||||
:caption: Four actors, three streams, one deduped feed.
|
||||
:alt: two streamer actors fan in to an aggregator then root
|
||||
|
||||
.. literalinclude:: ../../examples/full_fledged_streaming_service.py
|
||||
:caption: examples/full_fledged_streaming_service.py
|
||||
:language: python
|
||||
|
||||
What's going on?
|
||||
|
||||
- the root actor spawns ``'aggregator'`` which opens its *own*
|
||||
actor nursery and spawns ``'streamer_1'`` + ``'streamer_2'``: 4
|
||||
processes total, supervision nested two levels deep with zero
|
||||
special casing.
|
||||
|
||||
- ``aggregate()`` opens a one-way stream from each streamer and
|
||||
fans both into a single :func:`trio.open_memory_channel` via
|
||||
one local trio task per portal — in-actor fan-in riding trio's
|
||||
built-in backpressure end-to-end.
|
||||
|
||||
- duplicates get dropped via a ``set`` and the deduped sequence
|
||||
is *re-yielded* upward: ``aggregate()`` is itself an async gen
|
||||
being consumed over IPC by the root. Streams compose.
|
||||
|
||||
- when the seed runs out the streamer gens finish, the memory
|
||||
channel drains closed, the aggregator's gen returns and the
|
||||
root's ``async for`` ends; ``await an.cancel()`` then reaps the
|
||||
subtree. Every exit is awaited — if you can produce a zombie
|
||||
process from this, it **is a bug**.
|
||||
|
||||
Watch the tree breathe while it runs, using the README's
|
||||
signature process-monitor incantation::
|
||||
|
||||
$TERM -e watch -n 0.1 "pstree -a $$" \
|
||||
& python examples/full_fledged_streaming_service.py \
|
||||
&& kill $!
|
||||
|
||||
No extra threads, no fancy semaphores, no futures; all we need is
|
||||
``tractor``'s IPC.
|
||||
|
||||
Two streams, one portal
|
||||
-----------------------
|
||||
|
||||
Every ``open_stream_from()`` call starts its *own* remote task —
|
||||
even through the same portal — so two local consumer tasks can
|
||||
independently stream the same generator fn concurrently, both
|
||||
dialogs multiplexed over the single underlying IPC channel:
|
||||
|
||||
.. literalinclude:: ../../examples/multiple_streams_one_portal.py
|
||||
:caption: examples/multiple_streams_one_portal.py
|
||||
:language: python
|
||||
|
||||
The add-else-remove trick on the shared ``consumed`` list is the
|
||||
proof: each value arrives in *both* streams, getting appended by
|
||||
whichever task sees it first and removed by the other, so the
|
||||
list always ends up empty. Two streams, same data, zero
|
||||
interference.
|
||||
|
||||
This works because every dialog is keyed by its own context id
|
||||
(``Context.cid``) — any number of concurrent streams, contexts
|
||||
and one-shot RPCs share a single underlying
|
||||
:class:`tractor.Channel` per peer pair.
|
||||
|
||||
Fan-out inside an actor: ``MsgStream.subscribe()``
|
||||
--------------------------------------------------
|
||||
|
||||
The inverse pattern: *one* IPC stream feeding *many* local tasks.
|
||||
Instead of paying for N redundant cross-process streams, call
|
||||
:meth:`tractor.MsgStream.subscribe` to get a
|
||||
``BroadcastReceiver`` — a tokio-style broadcast channel from
|
||||
``tractor.trionics`` — which copies every received value to each
|
||||
subscribed task:
|
||||
|
||||
.. literalinclude:: ../../examples/streaming_broadcast_fanout.py
|
||||
:caption: examples/streaming_broadcast_fanout.py
|
||||
:language: python
|
||||
|
||||
Each task entering ``stream.subscribe()`` receives its own copy
|
||||
of everything sent from that point on. The underlying stream
|
||||
keeps pace with the *fastest* subscriber; a task falling more
|
||||
than the buffered window behind has its next receive raise
|
||||
``tractor.trionics.Lagged`` to say it lost data.
|
||||
|
||||
The broadcast handle stays duplex btw: it proxies ``send()``
|
||||
through to the underlying stream, so each subscriber task can
|
||||
keep talking upstream while consuming its fan-out copy.
|
||||
|
||||
.. warning::
|
||||
|
||||
``.subscribe()`` is **idempotent and non-reversible**: the
|
||||
first call permanently swaps the stream's receive machinery
|
||||
over to the internally allocated broadcaster. There's no
|
||||
un-subscribing back to the raw stream, so make sure you're ok
|
||||
with the (theoretical) overhead before opting in.
|
||||
|
||||
Consuming: ``async for`` and friends
|
||||
------------------------------------
|
||||
|
||||
``async for msg in stream:`` is just sugar over repeated
|
||||
``await stream.receive()``. The receive-side surface:
|
||||
|
||||
- ``receive()`` — next msg, or raises :exc:`trio.EndOfChannel`
|
||||
on a graceful far-end close (``async for`` translates that
|
||||
into a clean loop exit for you).
|
||||
|
||||
- ``receive_nowait()`` — opportunistic, non-blocking drain.
|
||||
|
||||
- ``closed`` — property flagging an already-ended stream.
|
||||
|
||||
Send-side it's just ``await stream.send(data)`` — one ``Yield``
|
||||
msg per call carrying any msgspec_-encodable payload (or
|
||||
whatever your ``pld_spec`` permits, see :doc:`/guide/context`).
|
||||
|
||||
End-of-stream: close vs. cancel
|
||||
-------------------------------
|
||||
|
||||
How a stream ends is part of the protocol; the runtime keeps the
|
||||
polite case and the violent case distinct:
|
||||
|
||||
- **graceful close**: the far side exits its stream block, its
|
||||
async gen returns, or it calls ``await stream.aclose()``. A
|
||||
``Stop`` msg is sent so your ``async for`` simply ends
|
||||
(``StopAsyncIteration``, via :exc:`trio.EndOfChannel` under the
|
||||
hood). A normal, non-error ending — the dialog's result phase
|
||||
proceeds as usual.
|
||||
|
||||
- **cancel or error**: no ``Stop`` is sent. Instead the
|
||||
cancel/error itself is relayed so the far end *knows* the
|
||||
dialog did not end on purpose and raises accordingly — a
|
||||
:exc:`tractor.ContextCancelled`, a boxed
|
||||
:exc:`tractor.RemoteActorError`, etc. See the cancellation
|
||||
section of :doc:`/guide/context` for exactly who raises what.
|
||||
|
||||
Tying it together: every ``MsgStream`` is **one-shot use**. Both
|
||||
endings are final — once closed a stream can't be re-opened and
|
||||
the supported "retry" is opening a fresh :class:`tractor.Context`
|
||||
(they're cheap).
|
||||
|
||||
.. seealso::
|
||||
|
||||
- :doc:`/guide/context` — the full ``Context`` lifecycle: the
|
||||
handshake, results, cancellation semantics and the
|
||||
overrun/backpressure knobs.
|
||||
|
||||
- :class:`tractor.MsgStream` and
|
||||
:meth:`tractor.Portal.open_stream_from` API docs.
|
||||
|
||||
- The zguide chapters our wire philosophy is named after:
|
||||
"`cheap or nasty`_" and `(un)protocol`_\ s.
|
||||
|
||||
.. _structured concurrency: https://en.wikipedia.org/wiki/Structured_concurrency
|
||||
.. _cheap or nasty: https://zguide.zeromq.org/docs/chapter7/#The-Cheap-or-Nasty-Pattern
|
||||
.. _(un)protocol: https://zguide.zeromq.org/docs/chapter7/#Unprotocols
|
||||
.. _msgspec: https://jcristharif.com/msgspec/
|
||||
|
|
@ -0,0 +1,256 @@
|
|||
Testing tips
|
||||
============
|
||||
|
||||
``tractor``'s test suite is a different kind of beast than your
|
||||
average single-proc pytest run: nearly every test spawns a real
|
||||
**process tree**, hammers on cancellation under structured
|
||||
concurrency (SC), and tears the whole thing down again — hundreds
|
||||
of times per session. This page collects the tips, knobs and
|
||||
one-liners that make hacking on (and with) the suite pleasant.
|
||||
|
||||
Running the suite
|
||||
-----------------
|
||||
|
||||
This is a uv_-managed project, so after cloning it's just::
|
||||
|
||||
uv sync --dev
|
||||
uv run pytest tests/
|
||||
|
||||
Expect a *lot* of process churn; the suite is effectively a
|
||||
rolling chaos exercise for the runtime.
|
||||
|
||||
The classic fix-iterate loop when something breaks::
|
||||
|
||||
# stop at the first failure
|
||||
uv run pytest tests/ -x
|
||||
|
||||
# then iterate on just the failures til green
|
||||
uv run pytest --lf -x
|
||||
|
||||
``--lf`` (last-failed) re-runs only what failed previously, so
|
||||
combined with ``-x`` you get a tight one-test-at-a-time repair
|
||||
loop.
|
||||
|
||||
Suite-specific flags
|
||||
********************
|
||||
|
||||
The repo auto-loads the bundled ``tractor._testing.pytest`` plugin
|
||||
(via ``addopts`` in ``pyproject.toml``) which adds a few extra
|
||||
flags:
|
||||
|
||||
- ``--spawn-backend <key>``: pick the process spawn backend for
|
||||
the session (default ``'trio'``); same keys as the
|
||||
``start_method`` runtime argument,
|
||||
|
||||
- ``--tpt-proto <key> [...]``: which IPC transport(s) opting-in
|
||||
suites should run against, eg. ``--tpt-proto uds``,
|
||||
|
||||
- ``--tpdb`` / ``--debug-mode``: flip on the ``debug_mode``
|
||||
fixture so debugger-aware tests boot their trees with the
|
||||
crash-REPL enabled,
|
||||
|
||||
- ``--enable-stackscope``: install the ``SIGUSR1`` task-tree dump
|
||||
handler in pytest *and* every spawned subactor — much lighter
|
||||
than a full debug-mode run when you only need stack visibility
|
||||
during a hang hunt,
|
||||
|
||||
- ``--ll <level>`` / ``--tl <level-or-spec>``: console loglevels;
|
||||
``--tl`` targets the ``tractor``-as-runtime logger and accepts
|
||||
a per-subsystem spec like ``'devx:runtime,trionics:cancel'``.
|
||||
|
||||
Watch the tree grow
|
||||
-------------------
|
||||
|
||||
The single most useful trick while the suite (or any ``tractor``
|
||||
app) runs: keep a live ``pstree`` view going in a side terminal::
|
||||
|
||||
watch -n 0.1 "pstree -a $(pgrep -f pytest)"
|
||||
|
||||
You'll see actor processes pop in and out of existence as each
|
||||
test builds and reaps its tree. Launch it *after* pytest is up
|
||||
(the pid is substituted once, at ``watch`` startup).
|
||||
|
||||
Every subactor also sets its OS process title (via
|
||||
``setproctitle``) to ``_subactor[<name>@<uuid-prefix>]`` so the
|
||||
tree view shows *which actor is which* at a glance — and targeted
|
||||
greps stay easy::
|
||||
|
||||
pgrep -af '_subactor\['
|
||||
|
||||
For a single example script, the repo's signature incantation
|
||||
spawns the watcher alongside your program and cleans it up after::
|
||||
|
||||
$TERM -e watch -n 0.1 "pstree -a $$" \
|
||||
& python examples/parallelism/single_func.py \
|
||||
&& kill $!
|
||||
|
||||
Env-var knobs
|
||||
-------------
|
||||
|
||||
Two env-vars override their corresponding runtime arguments
|
||||
*globally* — no application (or test) code changes required:
|
||||
|
||||
``TRACTOR_SPAWN_METHOD``
|
||||
Wins over any caller-passed ``start_method`` so you can drive
|
||||
the whole suite (or any app) under a different spawn backend::
|
||||
|
||||
TRACTOR_SPAWN_METHOD=mp_spawn uv run pytest tests/ -x
|
||||
|
||||
``TRACTOR_LOGLEVEL``
|
||||
Wins over any caller-passed ``loglevel``; crank (or silence)
|
||||
runtime console verbosity wholesale::
|
||||
|
||||
TRACTOR_LOGLEVEL=cancel uv run pytest tests/ -x -s
|
||||
|
||||
``TRACTOR_ENABLE_STACKSCOPE``
|
||||
Force-install the ``SIGUSR1`` task-tree dump handler in every
|
||||
actor, debug-mode or not; then
|
||||
``pkill --signal SIGUSR1 -f <part-of-cmd>`` dumps every
|
||||
actor's live ``trio`` task tree.
|
||||
|
||||
Debug mode vs. pytest capture
|
||||
-----------------------------
|
||||
|
||||
The tree-wide crash-to-REPL experience (``debug_mode=True`` plus
|
||||
``await tractor.pause()``) requires a **real tty**, and pytest's
|
||||
default output capturing swallows exactly that. When you want to
|
||||
interact with the REPL from inside a test run, disable capture::
|
||||
|
||||
uv run pytest tests/test_foo.py -x -s
|
||||
|
||||
(``-s`` is shorthand for ``--capture=no``.)
|
||||
|
||||
Tests should request the ``debug_mode`` fixture (driven by the
|
||||
``--tpdb`` flag) rather than hard-coding it, so that normal CI
|
||||
runs stay non-interactive.
|
||||
|
||||
For *automated* REPL interaction — asserting on prompt output,
|
||||
sending debugger commands — you can't just turn capture off;
|
||||
instead do what ``tests/devx/`` does: drive a child Python program
|
||||
through pexpect_ on a real pseudo-tty and pattern-match the
|
||||
``(Pdb+)`` prompts. See ``tests/devx/test_debugger.py`` for many
|
||||
worked patterns.
|
||||
|
||||
Examples *are* tests
|
||||
--------------------
|
||||
|
||||
Every script under ``examples/`` is run as a subprocess by
|
||||
``tests/test_docs_examples.py``; since these docs
|
||||
``literalinclude`` those same scripts, the code you read here is
|
||||
CI-verified on every push and can never silently rot B)
|
||||
|
||||
Conventions when adding a new example:
|
||||
|
||||
- make it a standalone runnable script with the usual guard::
|
||||
|
||||
if __name__ == '__main__':
|
||||
trio.run(main)
|
||||
|
||||
- it must exit cleanly (returncode ``0``) within the per-example
|
||||
timeout (~16s locally, with headroom auto-added in CI and under
|
||||
cpu-freq scaling) — keep sleeps short,
|
||||
|
||||
- any stderr line containing ``Error`` fails the test, so silence
|
||||
or assert-around expected error output,
|
||||
|
||||
- don't crank ``tractor`` logging inside an example: subprocess
|
||||
pipe **backpressure can deadlock** the run (ask us how we
|
||||
know..),
|
||||
|
||||
- filenames starting with ``_`` are skipped (the WIP convention),
|
||||
as are the special subdirs (``debugging/``, ``integration/``,
|
||||
``advanced_faults/``, ``trio/``) which are driven by their own
|
||||
dedicated suites instead.
|
||||
|
||||
Drop your script in, run the example suite, profit::
|
||||
|
||||
uv run pytest tests/test_docs_examples.py -x
|
||||
|
||||
Zombie cleanup
|
||||
--------------
|
||||
|
||||
First, the contract: ``tractor`` **always** reaps its children —
|
||||
if you can create a zombie process (without resorting to
|
||||
untrappable signals) it **is a bug**, please report it!
|
||||
|
||||
That said, while hacking on the *runtime itself* you can
|
||||
definitely wedge things — a ``SIGKILL``-ed pytest, a half-broken
|
||||
spawn backend — and strand subactor procs plus their shm segments
|
||||
and UDS socket files. The repo ships a dedicated cleanup tool::
|
||||
|
||||
uv run scripts/tractor-reap --shm --uds
|
||||
|
||||
It's SC-polite even as a reaper: matched processes get ``SIGINT``
|
||||
first with a bounded grace window — so actor runtimes can run
|
||||
their ``trio`` teardown paths — escalating to ``SIGKILL`` only as
|
||||
a last resort. The ``--shm`` sweep unlinks ``/dev/shm/`` segments
|
||||
that no live process has open (it leans on psutil_, already in
|
||||
your dev venv, to check live mappings and fds) and ``--uds``
|
||||
clears socket files whose binder pid is dead.
|
||||
|
||||
Testing your own ``tractor`` app
|
||||
--------------------------------
|
||||
|
||||
The same plugin the suite uses ships in the package, so your
|
||||
project can load it too::
|
||||
|
||||
[tool.pytest.ini_options]
|
||||
addopts = ['-p tractor._testing.pytest']
|
||||
|
||||
That buys you the CLI flags above plus a set of fixtures —
|
||||
``loglevel``, ``debug_mode``, ``reg_addr`` (a session-unique
|
||||
registrar address so concurrent runs and other live ``tractor``
|
||||
apps on the host can't cross-talk) — and the ``@tractor_test``
|
||||
decorator:
|
||||
|
||||
.. code:: python
|
||||
|
||||
import tractor
|
||||
from tractor._testing import tractor_test
|
||||
|
||||
@tractor_test
|
||||
async def test_my_service(
|
||||
reg_addr: tuple,
|
||||
loglevel: str,
|
||||
):
|
||||
# already inside a root actor's trio task!
|
||||
async with tractor.open_nursery() as an:
|
||||
...
|
||||
|
||||
The decorator boots a root actor around your (async) test fn,
|
||||
wires any of the special fixtures you declare (``reg_addr``,
|
||||
``loglevel``, ``start_method``, ``debug_mode``) into
|
||||
``open_root_actor()``, and runs the body as the root-most task
|
||||
under a wall-clock ``trio.fail_after()`` guard.
|
||||
|
||||
General advice that has served this suite well:
|
||||
|
||||
- bound waits with ``trio.fail_after()`` *inside* tests; global
|
||||
pytest timeout plugins interact badly with multi-process
|
||||
``trio`` teardown,
|
||||
|
||||
- use the ``reg_addr`` fixture (or otherwise randomize your
|
||||
registry addrs) so leftover registrars from prior runs can't
|
||||
contaminate lookups,
|
||||
|
||||
- assert on **structured outcomes** — eg.
|
||||
``RemoteActorError.boxed_type`` or
|
||||
``ContextCancelled.canceller`` — not on log text.
|
||||
|
||||
.. note::
|
||||
``tractor._testing`` is still an underscore-internal namespace:
|
||||
shipped and handy, but its API may shift between alpha
|
||||
releases.
|
||||
|
||||
(This page exists thanks to the ask in `#126`_.)
|
||||
|
||||
.. seealso::
|
||||
- :doc:`/guide/discovery` — how registrar wiring (the thing
|
||||
``reg_addr`` randomizes) works in the runtime proper.
|
||||
- :doc:`/project/dev-tips` — contributor-oriented extras:
|
||||
releases, log-system tracing, tree-monitoring recipes.
|
||||
|
||||
.. _uv: https://docs.astral.sh/uv/
|
||||
.. _pexpect: https://pexpect.readthedocs.io/en/stable/
|
||||
.. _psutil: https://psutil.readthedocs.io/en/latest/
|
||||
.. _#126: https://github.com/goodboy/tractor/issues/126
|
||||
752
docs/index.rst
752
docs/index.rst
|
|
@ -1,612 +1,154 @@
|
|||
.. tractor documentation master file, created by
|
||||
sphinx-quickstart on Sun Feb 9 22:26:51 2020.
|
||||
You can adapt this file completely to your liking, but it should at least
|
||||
contain the root `toctree` directive.
|
||||
.. image:: _static/tractor_logo_side.svg
|
||||
:class: hero-logo
|
||||
:align: center
|
||||
:alt: tractor
|
||||
|
||||
``tractor``
|
||||
===========
|
||||
tractor
|
||||
=======
|
||||
**distributed structured concurrency**: a
|
||||
multi-processing runtime built on (and shaped
|
||||
entirely like) trio_.
|
||||
|
||||
A `structured concurrent`_, async-native "`actor model`_" built on trio_ and multiprocessing_.
|
||||
``tractor`` provides parallelism via ``trio``
|
||||
*"actors"*: independent Python **processes** (ie.
|
||||
*non-shared-memory threads*) each running a ``trio``
|
||||
task tree, all composed into a *distributed
|
||||
supervision tree* with end-to-end `structured
|
||||
concurrency`_ (SC) — spawning, cancellation, error
|
||||
propagation and teardown that work **across
|
||||
processes** (and hosts) exactly the way they work
|
||||
across tasks.
|
||||
|
||||
.. margin:: tl;dr
|
||||
|
||||
It's **just** ``trio``, but with nurseries that
|
||||
spawn *processes* and streams that cross them. If
|
||||
you can read a ``trio`` program you can read a
|
||||
``tractor`` one — that's the whole pitch.
|
||||
|
||||
Sixty seconds of why
|
||||
--------------------
|
||||
Spawn one actor per core, crash the root on purpose,
|
||||
and watch the runtime contain the blast: errors
|
||||
propagate, *every* child is reaped, zero zombies —
|
||||
guaranteed (it's a bug otherwise).
|
||||
|
||||
.. literalinclude:: ../examples/parallelism/we_are_processes.py
|
||||
:caption: examples/parallelism/we_are_processes.py
|
||||
:language: python
|
||||
|
||||
Like every snippet in these docs this file lives in
|
||||
the repo's ``examples/`` dir and runs under CI — docs
|
||||
code that can't rot.
|
||||
|
||||
Dig in
|
||||
------
|
||||
.. grid:: 1 2 2 3
|
||||
:gutter: 3
|
||||
|
||||
.. grid-item-card:: Get started
|
||||
:link: start/index
|
||||
:link-type: doc
|
||||
|
||||
Install + your first actor tree in ~20 lines;
|
||||
causality, daemons and the trynamic scene.
|
||||
|
||||
.. grid-item-card:: The big ideas
|
||||
:link: explain/sc-distributed
|
||||
:link-type: doc
|
||||
|
||||
SC across processes, distilled — then the
|
||||
runtime architecture under it.
|
||||
|
||||
.. grid-item-card:: Debug like a local
|
||||
:link: guide/debugging
|
||||
:link-type: doc
|
||||
|
||||
``await tractor.pause()`` anywhere in the
|
||||
tree: one terminal, every process, zero
|
||||
socket-juggling.
|
||||
|
||||
.. grid-item-card:: Streaming + contexts
|
||||
:link: guide/context
|
||||
:link-type: doc
|
||||
|
||||
Bidirectional, cancellation-safe msg streams
|
||||
between any two actors.
|
||||
|
||||
.. grid-item-card:: Guides
|
||||
:link: guide/index
|
||||
:link-type: doc
|
||||
|
||||
RPC, supervision, clustering, "infected
|
||||
asyncio", typed msging + more.
|
||||
|
||||
.. grid-item-card:: API reference
|
||||
:link: api/index
|
||||
:link-type: doc
|
||||
|
||||
The curated public surface; everything
|
||||
importable from ``tractor``.
|
||||
|
||||
Features
|
||||
--------
|
||||
- **It's just a** ``trio`` **API** — same nursery
|
||||
discipline, same cancellation semantics, one level
|
||||
up the process tree.
|
||||
- *Infinitely nestable* process trees: sub-actors can
|
||||
spawn sub-actors, supervision stays transitive.
|
||||
- A "native UX" **multi-process debugger REPL**:
|
||||
built on pdbp_ with tree-wide tty locking (see
|
||||
:doc:`guide/debugging`).
|
||||
- Built-in, cancellation-safe **bidirectional
|
||||
streaming** via a `cheap or nasty`_ `(un)protocol`_.
|
||||
- **Typed IPC**: `msgspec`_-backed wire msgs with
|
||||
optional per-dialog payload specs
|
||||
(:doc:`guide/msging`).
|
||||
- Swappable process-spawn backends + modular IPC
|
||||
transports (TCP today, UDS on same-host, more
|
||||
planned).
|
||||
- Optionally distributed_: the same APIs work over
|
||||
multiple hosts as on multiple cores.
|
||||
- "**Infected** ``asyncio``" mode: SC-supervise
|
||||
``asyncio`` tasks from ``trio``
|
||||
(:doc:`guide/asyncio`).
|
||||
- ``trio`` extension goodies via ``tractor.trionics``
|
||||
(acm gathering, single-resource caching, broadcast
|
||||
channels).
|
||||
|
||||
Where do i start!?
|
||||
------------------
|
||||
The first step to grok ``tractor`` is to get an
|
||||
intermediate knowledge of ``trio`` and **structured
|
||||
concurrency** B)
|
||||
|
||||
Some great places to start are,
|
||||
|
||||
- the seminal `blog post`_,
|
||||
- obviously the `trio docs`_,
|
||||
- wikipedia's nascent SC_ page,
|
||||
- the fancy diagrams @ libdill-docs_,
|
||||
|
||||
then come back and hit :doc:`start/quickstart`.
|
||||
|
||||
.. toctree::
|
||||
:maxdepth: 1
|
||||
:caption: Contents:
|
||||
:hidden:
|
||||
:maxdepth: 2
|
||||
|
||||
Get started <start/index>
|
||||
Big ideas <explain/index>
|
||||
Guides <guide/index>
|
||||
API <api/index>
|
||||
Project <project/index>
|
||||
|
||||
.. _actor model: https://en.wikipedia.org/wiki/Actor_model
|
||||
.. _trio: https://github.com/python-trio/trio
|
||||
.. _multiprocessing: https://en.wikipedia.org/wiki/Multiprocessing
|
||||
.. _trionic: https://trio.readthedocs.io/en/latest/design.html#high-level-design-principles
|
||||
.. _async sandwich: https://trio.readthedocs.io/en/latest/tutorial.html#async-sandwich
|
||||
.. _structured concurrent: https://trio.discourse.group/t/concise-definition-of-structured-concurrency/228
|
||||
|
||||
|
||||
``tractor`` is an attempt to bring trionic_ `structured concurrency`_ to
|
||||
distributed multi-core Python; it aims to be the Python multi-processing
|
||||
framework *you always wanted*.
|
||||
|
||||
``tractor`` lets you spawn ``trio`` *"actors"*: processes which each run
|
||||
a ``trio`` scheduled task tree (also known as an `async sandwich`_).
|
||||
*Actors* communicate by exchanging asynchronous messages_ and avoid
|
||||
sharing any state. This model allows for highly distributed software
|
||||
architecture which works just as well on multiple cores as it does over
|
||||
many hosts.
|
||||
|
||||
The first step to grok ``tractor`` is to get the basics of ``trio`` down.
|
||||
A great place to start is the `trio docs`_ and this `blog post`_.
|
||||
|
||||
.. _messages: https://en.wikipedia.org/wiki/Message_passing
|
||||
.. _trio docs: https://trio.readthedocs.io/en/latest/
|
||||
.. _structured concurrency: https://en.wikipedia.org/wiki/Structured_concurrency
|
||||
.. _SC: https://en.wikipedia.org/wiki/Structured_concurrency
|
||||
.. _blog post: https://vorpus.org/blog/notes-on-structured-concurrency-or-go-statement-considered-harmful/
|
||||
.. _structured concurrency: https://vorpus.org/blog/notes-on-structured-concurrency-or-go-statement-considered-harmful/
|
||||
|
||||
|
||||
Install
|
||||
-------
|
||||
No PyPi release yet!
|
||||
|
||||
::
|
||||
|
||||
pip install git+git://github.com/goodboy/tractor.git
|
||||
|
||||
|
||||
Feel like saying hi?
|
||||
--------------------
|
||||
This project is very much coupled to the ongoing development of
|
||||
``trio`` (i.e. ``tractor`` gets all its ideas from that brilliant
|
||||
community). If you want to help, have suggestions or just want to
|
||||
say hi, please feel free to ping me on the `trio gitter channel`_!
|
||||
|
||||
.. _trio gitter channel: https://gitter.im/python-trio/general
|
||||
|
||||
|
||||
|
||||
Philosophy
|
||||
----------
|
||||
Our tenets non-comprehensively include:
|
||||
|
||||
- strict adherence to the `concept-in-progress`_ of *structured concurrency*
|
||||
- no spawning of processes *willy-nilly*; causality_ is paramount!
|
||||
- (remote) errors `always propagate`_ back to the parent supervisor
|
||||
- verbatim support for ``trio``'s cancellation_ system
|
||||
- `shared nothing architecture`_
|
||||
- no use of *proxy* objects or shared references between processes
|
||||
- an immersive debugging experience
|
||||
- anti-fragility through `chaos engineering`_
|
||||
|
||||
``tractor`` is an actor-model-*like* system in the sense that it adheres
|
||||
to the `3 axioms`_ but does not (yet) fulfil all "unrequirements_" in
|
||||
practise. It is an experiment in applying `structured concurrency`_
|
||||
constraints on a parallel processing system where multiple Python
|
||||
processes exist over many hosts but no process can outlive its parent.
|
||||
In `erlang` parlance, it is an architecture where every process has
|
||||
a mandatory supervisor enforced by the type system. The API design is
|
||||
almost exclusively inspired by trio_'s concepts and primitives (though
|
||||
we often lag a little). As a distributed computing system `tractor`
|
||||
attempts to place sophistication at the correct layer such that
|
||||
concurrency primitives are powerful yet simple, making it easy to build
|
||||
complex systems (you can build a "worker pool" architecture but it's
|
||||
definitely not required). There is first class support for inter-actor
|
||||
streaming using `async generators`_ and ongoing work toward a functional
|
||||
reactive style for IPC.
|
||||
|
||||
.. warning:: ``tractor`` is in alpha-alpha and is expected to change rapidly!
|
||||
Expect nothing to be set in stone. Your ideas about where it should go
|
||||
are greatly appreciated!
|
||||
|
||||
.. _concept-in-progress: https://trio.discourse.group/t/structured-concurrency-kickoff/55
|
||||
.. _3 axioms: https://en.wikipedia.org/wiki/Actor_model#Fundamental_concepts
|
||||
.. _unrequirements: https://en.wikipedia.org/wiki/Actor_model#Direct_communication_and_asynchrony
|
||||
.. _async generators: https://www.python.org/dev/peps/pep-0525/
|
||||
.. _always propagate: https://trio.readthedocs.io/en/latest/design.html#exceptions-always-propagate
|
||||
.. _causality: https://vorpus.org/blog/some-thoughts-on-asynchronous-api-design-in-a-post-asyncawait-world/#c-c-c-c-causality-breaker
|
||||
.. _shared nothing architecture: https://en.wikipedia.org/wiki/Shared-nothing_architecture
|
||||
.. _cancellation: https://trio.readthedocs.io/en/latest/reference-core.html#cancellation-and-timeouts
|
||||
.. _channels: https://en.wikipedia.org/wiki/Channel_(programming)
|
||||
.. _chaos engineering: http://principlesofchaos.org/
|
||||
|
||||
|
||||
Examples
|
||||
--------
|
||||
Note, if you are on Windows please be sure to see the :ref:`gotchas
|
||||
<windowsgotchas>` section before trying these.
|
||||
|
||||
|
||||
A trynamic first scene
|
||||
**********************
|
||||
Let's direct a couple *actors* and have them run their lines for
|
||||
the hip new film we're shooting:
|
||||
|
||||
.. literalinclude:: ../examples/a_trynamic_first_scene.py
|
||||
|
||||
We spawn two *actors*, *donny* and *gretchen*.
|
||||
Each actor starts up and executes their *main task* defined by an
|
||||
async function, ``say_hello()``. The function instructs each actor
|
||||
to find their partner and say hello by calling their partner's
|
||||
``hi()`` function using something called a *portal*. Each actor
|
||||
receives a response and relays that back to the parent actor (in
|
||||
this case our "director" executing ``main()``).
|
||||
|
||||
|
||||
Actor spawning and causality
|
||||
****************************
|
||||
``tractor`` tries to take ``trio``'s concept of causal task lifetimes
|
||||
to multi-process land. Accordingly, ``tractor``'s *actor nursery* behaves
|
||||
similar to ``trio``'s nursery_. That is, ``tractor.open_nursery()``
|
||||
opens an ``ActorNursery`` which **must** wait on spawned *actors* to complete
|
||||
(or error) in the same causal_ way ``trio`` waits on spawned subtasks.
|
||||
This includes errors from any one actor causing all other actors
|
||||
spawned by the same nursery to be cancelled_.
|
||||
|
||||
To spawn an actor and run a function in it, open a *nursery block*
|
||||
and use the ``run_in_actor()`` method:
|
||||
|
||||
.. literalinclude:: ../examples/actor_spawning_and_causality.py
|
||||
|
||||
What's going on?
|
||||
|
||||
- an initial *actor* is started with ``trio.run()`` and told to execute
|
||||
its main task_: ``main()``
|
||||
|
||||
- inside ``main()`` an actor is *spawned* using an ``ActorNusery`` and is told
|
||||
to run a single function: ``cellar_door()``
|
||||
|
||||
- a ``portal`` instance (we'll get to what it is shortly)
|
||||
returned from ``nursery.run_in_actor()`` is used to communicate with
|
||||
the newly spawned *sub-actor*
|
||||
|
||||
- the second actor, *some_linguist*, in a new *process* running a new ``trio`` task_
|
||||
then executes ``cellar_door()`` and returns its result over a *channel* back
|
||||
to the parent actor
|
||||
|
||||
- the parent actor retrieves the subactor's *final result* using ``portal.result()``
|
||||
much like you'd expect from a future_.
|
||||
|
||||
This ``run_in_actor()`` API should look very familiar to users of
|
||||
``asyncio``'s `run_in_executor()`_ which uses a ``concurrent.futures`` Executor_.
|
||||
|
||||
Since you might also want to spawn long running *worker* or *daemon*
|
||||
actors, each actor's *lifetime* can be determined based on the spawn
|
||||
method:
|
||||
|
||||
- if the actor is spawned using ``run_in_actor()`` it terminates when
|
||||
its *main* task completes (i.e. when the (async) function submitted
|
||||
to it *returns*). The ``with tractor.open_nursery()`` exits only once
|
||||
all actors' main function/task complete (just like the nursery_ in ``trio``)
|
||||
|
||||
- actors can be spawned to *live forever* using the ``start_actor()``
|
||||
method and act like an RPC daemon that runs indefinitely (the
|
||||
``with tractor.open_nursery()`` won't exit) until cancelled_
|
||||
|
||||
Here is a similar example using the latter method:
|
||||
|
||||
.. literalinclude:: ../examples/actor_spawning_and_causality_with_daemon.py
|
||||
|
||||
The ``enable_modules`` `kwarg` above is a list of module path
|
||||
strings that will be loaded and made accessible for execution in the
|
||||
remote actor through a call to ``Portal.run()``. For now this is
|
||||
a simple mechanism to restrict the functionality of the remote
|
||||
(and possibly daemonized) actor and uses Python's module system to
|
||||
limit the allowed remote function namespace(s).
|
||||
|
||||
``tractor`` is opinionated about the underlying threading model used for
|
||||
each *actor*. Since Python has a GIL and an actor model by definition
|
||||
shares no state between actors, it fits naturally to use a multiprocessing_
|
||||
``Process``. This allows ``tractor`` programs to leverage not only multi-core
|
||||
hardware but also distribute over many hardware hosts (each *actor* can talk
|
||||
to all others with ease over standard network protocols).
|
||||
|
||||
.. _task: https://trio.readthedocs.io/en/latest/reference-core.html#tasks-let-you-do-multiple-things-at-once
|
||||
.. _nursery: https://trio.readthedocs.io/en/latest/reference-core.html#nurseries-and-spawning
|
||||
.. _causal: https://vorpus.org/blog/some-thoughts-on-asynchronous-api-design-in-a-post-asyncawait-world/#causality
|
||||
.. _cancelled: https://trio.readthedocs.io/en/latest/reference-core.html#child-tasks-and-cancellation
|
||||
.. _run_in_executor(): https://docs.python.org/3/library/asyncio-eventloop.html#asyncio.loop.run_in_executor
|
||||
.. _Executor: https://docs.python.org/3/library/concurrent.futures.html#concurrent.futures.Executor
|
||||
|
||||
|
||||
Cancellation
|
||||
************
|
||||
``tractor`` supports ``trio``'s cancellation_ system verbatim.
|
||||
Cancelling a nursery block cancels all actors spawned by it.
|
||||
Eventually ``tractor`` plans to support different `supervision strategies`_ like ``erlang``.
|
||||
|
||||
.. _supervision strategies: http://erlang.org/doc/man/supervisor.html#sup_flags
|
||||
|
||||
|
||||
Remote error propagation
|
||||
************************
|
||||
Any task invoked in a remote actor should ship any error(s) back to the calling
|
||||
actor where it is raised and expected to be dealt with. This way remote actors
|
||||
are never cancelled unless explicitly asked or there's a bug in ``tractor`` itself.
|
||||
|
||||
.. literalinclude:: ../examples/remote_error_propagation.py
|
||||
|
||||
|
||||
You'll notice the nursery cancellation conducts a *one-cancels-all*
|
||||
supervisory strategy `exactly like trio`_. The plan is to add more
|
||||
`erlang strategies`_ in the near future by allowing nurseries to accept
|
||||
a ``Supervisor`` type.
|
||||
|
||||
.. _exactly like trio: https://trio.readthedocs.io/en/latest/reference-core.html#cancellation-semantics
|
||||
.. _erlang strategies: http://learnyousomeerlang.com/supervisors
|
||||
|
||||
|
||||
IPC using *portals*
|
||||
*******************
|
||||
``tractor`` introduces the concept of a *portal* which is an API
|
||||
borrowed_ from ``trio``. A portal may seem similar to the idea of
|
||||
a RPC future_ except a *portal* allows invoking remote *async* functions and
|
||||
generators and intermittently blocking to receive responses. This allows
|
||||
for fully async-native IPC between actors.
|
||||
|
||||
When you invoke another actor's routines using a *portal* it looks as though
|
||||
it was called locally in the current actor. So when you see a call to
|
||||
``await portal.run()`` what you get back is what you'd expect
|
||||
to if you'd called the function directly in-process. This approach avoids
|
||||
the need to add any special RPC *proxy* objects to the library by instead just
|
||||
relying on the built-in (async) function calling semantics and protocols of Python.
|
||||
|
||||
Depending on the function type ``Portal.run()`` tries to
|
||||
correctly interface exactly like a local version of the remote
|
||||
built-in Python *function type*. Currently async functions, generators,
|
||||
and regular functions are supported. Inspiration for this API comes
|
||||
`remote function execution`_ but without the client code being
|
||||
concerned about the underlying channels_ system or shipping code
|
||||
over the network.
|
||||
|
||||
This *portal* approach turns out to be paricularly exciting with the
|
||||
introduction of `asynchronous generators`_ in Python 3.6! It means that
|
||||
actors can compose nicely in a data streaming pipeline.
|
||||
|
||||
.. _exactly like trio: https://trio.readthedocs.io/en/latest/reference-core.html#cancellation-semantics
|
||||
|
||||
Streaming
|
||||
*********
|
||||
By now you've figured out that ``tractor`` lets you spawn process based
|
||||
*actors* that can invoke cross-process (async) functions and all with
|
||||
structured concurrency built in. But the **real cool stuff** is the
|
||||
native support for cross-process *streaming*.
|
||||
|
||||
|
||||
Asynchronous generators
|
||||
+++++++++++++++++++++++
|
||||
The default streaming function is simply an async generator definition.
|
||||
Every value *yielded* from the generator is delivered to the calling
|
||||
portal exactly like if you had invoked the function in-process meaning
|
||||
you can ``async for`` to receive each value on the calling side.
|
||||
|
||||
As an example here's a parent actor that streams for 1 second from a
|
||||
spawned subactor:
|
||||
|
||||
.. literalinclude:: ../examples/asynchronous_generators.py
|
||||
|
||||
By default async generator functions are treated as inter-actor
|
||||
*streams* when invoked via a portal (how else could you really interface
|
||||
with them anyway) so no special syntax to denote the streaming *service*
|
||||
is necessary.
|
||||
|
||||
|
||||
Channels and Contexts
|
||||
+++++++++++++++++++++
|
||||
If you aren't fond of having to write an async generator to stream data
|
||||
between actors (or need something more flexible) you can instead use
|
||||
a ``Context``. A context wraps an actor-local spawned task and
|
||||
a ``Channel`` so that tasks executing across multiple processes can
|
||||
stream data to one another using a low level, request oriented API.
|
||||
|
||||
A ``Channel`` wraps an underlying *transport* and *interchange* format
|
||||
to enable *inter-actor-communication*. In its present state ``tractor``
|
||||
uses TCP and msgpack_.
|
||||
|
||||
As an example if you wanted to create a streaming server without writing
|
||||
an async generator that *yields* values you instead define a decorated
|
||||
async function:
|
||||
|
||||
.. code:: python
|
||||
|
||||
@tractor.stream
|
||||
async def streamer(ctx: tractor.Context, rate: int = 2) -> None:
|
||||
"""A simple web response streaming server.
|
||||
"""
|
||||
while True:
|
||||
val = await web_request('http://data.feed.com')
|
||||
|
||||
# this is the same as ``yield`` in the async gen case
|
||||
await ctx.send_yield(val)
|
||||
|
||||
await trio.sleep(1 / rate)
|
||||
|
||||
|
||||
You must decorate the function with ``@tractor.stream`` and declare
|
||||
a ``ctx`` argument as the first in your function signature and then
|
||||
``tractor`` will treat the async function like an async generator - as
|
||||
a stream from the calling/client side.
|
||||
|
||||
This turns out to be handy particularly if you have multiple tasks
|
||||
pushing responses concurrently:
|
||||
|
||||
.. code:: python
|
||||
|
||||
async def streamer(
|
||||
ctx: tractor.Context,
|
||||
rate: int = 2
|
||||
) -> None:
|
||||
"""A simple web response streaming server.
|
||||
"""
|
||||
while True:
|
||||
val = await web_request(url)
|
||||
|
||||
# this is the same as ``yield`` in the async gen case
|
||||
await ctx.send_yield(val)
|
||||
|
||||
await trio.sleep(1 / rate)
|
||||
|
||||
|
||||
@tractor.stream
|
||||
async def stream_multiple_sources(
|
||||
ctx: tractor.Context,
|
||||
sources: List[str]
|
||||
) -> None:
|
||||
async with trio.open_nursery() as n:
|
||||
for url in sources:
|
||||
n.start_soon(streamer, ctx, url)
|
||||
|
||||
|
||||
The context notion comes from the context_ in nanomsg_.
|
||||
|
||||
.. _context: https://nanomsg.github.io/nng/man/tip/nng_ctx.5
|
||||
.. _msgpack: https://en.wikipedia.org/wiki/MessagePack
|
||||
|
||||
|
||||
|
||||
A full fledged streaming service
|
||||
++++++++++++++++++++++++++++++++
|
||||
Alright, let's get fancy.
|
||||
|
||||
Say you wanted to spawn two actors which each pull data feeds from
|
||||
two different sources (and wanted this work spread across 2 cpus).
|
||||
You also want to aggregate these feeds, do some processing on them and then
|
||||
deliver the final result stream to a client (or in this case parent) actor
|
||||
and print the results to your screen:
|
||||
|
||||
.. literalinclude:: ../examples/full_fledged_streaming_service.py
|
||||
|
||||
Here there's four actors running in separate processes (using all the
|
||||
cores on you machine). Two are streaming by *yielding* values from the
|
||||
``stream_data()`` async generator, one is aggregating values from
|
||||
those two in ``aggregate()`` (also an async generator) and shipping the
|
||||
single stream of unique values up the parent actor (the ``'MainProcess'``
|
||||
as ``multiprocessing`` calls it) which is running ``main()``.
|
||||
|
||||
.. _future: https://en.wikipedia.org/wiki/Futures_and_promises
|
||||
.. _borrowed:
|
||||
https://trio.readthedocs.io/en/latest/reference-core.html#getting-back-into-the-trio-thread-from-another-thread
|
||||
.. _asynchronous generators: https://www.python.org/dev/peps/pep-0525/
|
||||
.. _remote function execution: https://codespeak.net/execnet/example/test_info.html#remote-exec-a-function-avoiding-inlined-source-part-i
|
||||
|
||||
|
||||
Actor local (aka *process global*) variables
|
||||
********************************************
|
||||
Although ``tractor`` uses a *shared-nothing* architecture between
|
||||
processes you can of course share state between tasks running *within*
|
||||
an actor (since a `trio.run()` runtime is single threaded). ``trio``
|
||||
tasks spawned via multiple RPC calls to an actor can modify
|
||||
*process-global-state* defined using Python module attributes:
|
||||
|
||||
.. code:: python
|
||||
|
||||
|
||||
# a per process cache
|
||||
_actor_cache: dict[str, bool] = {}
|
||||
|
||||
|
||||
def ping_endpoints(endpoints: List[str]):
|
||||
"""Start a polling process which runs completely separate
|
||||
from our root actor/process.
|
||||
|
||||
"""
|
||||
|
||||
# This runs in a new process so no changes # will propagate
|
||||
# back to the parent actor
|
||||
while True:
|
||||
|
||||
for ep in endpoints:
|
||||
status = await check_endpoint_is_up(ep)
|
||||
_actor_cache[ep] = status
|
||||
|
||||
await trio.sleep(0.5)
|
||||
|
||||
|
||||
async def get_alive_endpoints():
|
||||
|
||||
nonlocal _actor_cache
|
||||
|
||||
return {key for key, value in _actor_cache.items() if value}
|
||||
|
||||
|
||||
async def main():
|
||||
|
||||
async with tractor.open_nursery() as n:
|
||||
|
||||
portal = await n.run_in_actor(ping_endpoints)
|
||||
|
||||
# print the alive endpoints after 3 seconds
|
||||
await trio.sleep(3)
|
||||
|
||||
# this is submitted to be run in our "ping_endpoints" actor
|
||||
print(await portal.run(get_alive_endpoints))
|
||||
|
||||
|
||||
You can pass any kind of (`msgpack`) serializable data between actors using
|
||||
function call semantics but building out a state sharing system per-actor
|
||||
is totally up to you.
|
||||
|
||||
|
||||
Service Discovery
|
||||
*****************
|
||||
Though it will be built out much more in the near future, ``tractor``
|
||||
currently keeps track of actors by ``(name: str, id: str)`` using a
|
||||
special actor called the *arbiter*. Currently the *arbiter* must exist
|
||||
on a host (or it will be created if one can't be found) and keeps a
|
||||
simple ``dict`` of actor names to sockets for discovery by other actors.
|
||||
Obviously this can be made more sophisticated (help me with it!) but for
|
||||
now it does the trick.
|
||||
|
||||
To find the arbiter from the current actor use the ``get_arbiter()`` function and to
|
||||
find an actor's socket address by name use the ``find_actor()`` function:
|
||||
|
||||
.. literalinclude:: ../examples/service_discovery.py
|
||||
|
||||
The ``name`` value you should pass to ``find_actor()`` is the one you passed as the
|
||||
*first* argument to either ``trio.run()`` or ``ActorNursery.start_actor()``.
|
||||
|
||||
|
||||
Running actors standalone
|
||||
*************************
|
||||
You don't have to spawn any actors using ``open_nursery()`` if you just
|
||||
want to run a single actor that connects to an existing cluster.
|
||||
All the comms and arbiter registration stuff still works. This can
|
||||
somtimes turn out being handy when debugging mult-process apps when you
|
||||
need to hop into a debugger. You just need to pass the existing
|
||||
*arbiter*'s socket address you'd like to connect to:
|
||||
|
||||
.. code:: python
|
||||
|
||||
import trio
|
||||
import tractor
|
||||
|
||||
async def main():
|
||||
|
||||
async with tractor.open_root_actor(
|
||||
arbiter_addr=('192.168.0.10', 1616)
|
||||
):
|
||||
await trio.sleep_forever()
|
||||
|
||||
trio.run(main)
|
||||
|
||||
|
||||
Choosing a process spawning backend
|
||||
***********************************
|
||||
``tractor`` is architected to support multiple actor (sub-process)
|
||||
spawning backends. Specific defaults are chosen based on your system
|
||||
but you can also explicitly select a backend of choice at startup
|
||||
via a ``start_method`` kwarg to ``tractor.open_nursery()``.
|
||||
|
||||
Currently the options available are:
|
||||
|
||||
- ``trio``: a ``trio``-native spawner which is an async wrapper around ``subprocess``
|
||||
- ``spawn``: one of the stdlib's ``multiprocessing`` `start methods`_
|
||||
- ``forkserver``: a faster ``multiprocessing`` variant that is Unix only
|
||||
|
||||
.. _start methods: https://docs.python.org/3.8/library/multiprocessing.html#contexts-and-start-methods
|
||||
|
||||
|
||||
``trio``
|
||||
++++++++
|
||||
The ``trio`` backend offers a lightweight async wrapper around ``subprocess`` from the standard library and takes advantage of the ``trio.`` `open_process`_ API.
|
||||
|
||||
.. _open_process: https://trio.readthedocs.io/en/stable/reference-io.html#spawning-subprocesses
|
||||
|
||||
|
||||
``multiprocessing``
|
||||
+++++++++++++++++++
|
||||
There is support for the stdlib's ``multiprocessing`` `start methods`_.
|
||||
Note that on Windows *spawn* it the only supported method and on \*nix
|
||||
systems *forkserver* is the best method for speed but has the caveat
|
||||
that it will break easily (hangs due to broken pipes) if spawning actors
|
||||
using nested nurseries.
|
||||
|
||||
In general, the ``multiprocessing`` backend **has not proven reliable**
|
||||
for handling errors from actors more then 2 nurseries *deep* (see `#89`_).
|
||||
If you for some reason need this consider sticking with alternative
|
||||
backends.
|
||||
|
||||
.. _#89: https://github.com/goodboy/tractor/issues/89
|
||||
|
||||
.. _windowsgotchas:
|
||||
|
||||
Windows "gotchas"
|
||||
^^^^^^^^^^^^^^^^^
|
||||
On Windows (which requires the use of the stdlib's `multiprocessing`
|
||||
package) there are some gotchas. Namely, the need for calling
|
||||
`freeze_support()`_ inside the ``__main__`` context. Additionally you
|
||||
may need place you `tractor` program entry point in a seperate
|
||||
`__main__.py` module in your package in order to avoid an error like the
|
||||
following ::
|
||||
|
||||
Traceback (most recent call last):
|
||||
File "C:\ProgramData\Miniconda3\envs\tractor19030601\lib\site-packages\tractor\_actor.py", line 234, in _get_rpc_func
|
||||
return getattr(self._mods[ns], funcname)
|
||||
KeyError: '__mp_main__'
|
||||
|
||||
|
||||
To avoid this, the following is the **only code** that should be in your
|
||||
main python module of the program:
|
||||
|
||||
.. code:: python
|
||||
|
||||
# application/__main__.py
|
||||
import trio
|
||||
import tractor
|
||||
import multiprocessing
|
||||
from . import tractor_app
|
||||
|
||||
if __name__ == '__main__':
|
||||
multiprocessing.freeze_support()
|
||||
trio.run(tractor_app.main)
|
||||
|
||||
And execute as::
|
||||
|
||||
python -m application
|
||||
|
||||
|
||||
As an example we use the following code to test all documented examples
|
||||
in the test suite on windows:
|
||||
|
||||
.. literalinclude:: ../examples/__main__.py
|
||||
|
||||
See `#61`_ and `#79`_ for further details.
|
||||
|
||||
.. _freeze_support(): https://docs.python.org/3/library/multiprocessing.html#multiprocessing.freeze_support
|
||||
.. _#61: https://github.com/goodboy/tractor/pull/61#issuecomment-470053512
|
||||
.. _#79: https://github.com/goodboy/tractor/pull/79
|
||||
|
||||
|
||||
Enabling logging
|
||||
****************
|
||||
Considering how complicated distributed software can become it helps to know
|
||||
what exactly it's doing (even at the lowest levels). Luckily ``tractor`` has
|
||||
tons of logging throughout the core. ``tractor`` isn't opinionated on
|
||||
how you use this information and users are expected to consume log messages in
|
||||
whichever way is appropriate for the system at hand. That being said, when hacking
|
||||
on ``tractor`` there is a prettified console formatter which you can enable to
|
||||
see what the heck is going on. Just put the following somewhere in your code:
|
||||
|
||||
.. code:: python
|
||||
|
||||
from tractor.log import get_console_log
|
||||
log = get_console_log('trace')
|
||||
|
||||
|
||||
What the future holds
|
||||
---------------------
|
||||
Stuff I'd like to see ``tractor`` do real soon:
|
||||
|
||||
- TLS_, duh.
|
||||
- erlang-like supervisors_
|
||||
- native support for `nanomsg`_ as a channel transport
|
||||
- native `gossip protocol`_ support for service discovery and arbiter election
|
||||
- a distributed log ledger for tracking cluster behaviour
|
||||
- a slick multi-process aware debugger much like in celery_
|
||||
but with better `pdb++`_ support
|
||||
- an extensive `chaos engineering`_ test suite
|
||||
- support for reactive programming primitives and native support for asyncitertools_ like libs
|
||||
- introduction of a `capability-based security`_ model
|
||||
|
||||
.. _TLS: https://trio.readthedocs.io/en/latest/reference-io.html#ssl-tls-support
|
||||
.. _supervisors: https://github.com/goodboy/tractor/issues/22
|
||||
.. _nanomsg: https://nanomsg.github.io/nng/index.html
|
||||
.. _gossip protocol: https://en.wikipedia.org/wiki/Gossip_protocol
|
||||
.. _celery: http://docs.celeryproject.org/en/latest/userguide/debugging.html
|
||||
.. _asyncitertools: https://github.com/vodik/asyncitertools
|
||||
.. _pdb++: https://github.com/antocuni/pdb
|
||||
.. _capability-based security: https://en.wikipedia.org/wiki/Capability-based_security
|
||||
.. _trio docs: https://trio.readthedocs.io/en/latest/
|
||||
.. _libdill-docs: https://sustrik.github.io/libdill/structured-concurrency.html
|
||||
.. _pdbp: https://github.com/mdmintz/pdbp
|
||||
.. _msgspec: https://jcristharif.com/msgspec/
|
||||
.. _cheap or nasty: https://zguide.zeromq.org/docs/chapter7/#The-Cheap-or-Nasty-Pattern
|
||||
.. _(un)protocol: https://zguide.zeromq.org/docs/chapter7/#Unprotocols
|
||||
.. _distributed: https://en.wikipedia.org/wiki/Distributed_computing
|
||||
|
|
|
|||
|
|
@ -0,0 +1 @@
|
|||
.. include:: ../../NEWS.rst
|
||||
|
|
@ -0,0 +1,133 @@
|
|||
Hot tips for ``tractor`` hackers
|
||||
================================
|
||||
|
||||
This is a (perpetually WIP) guide for newcomers to the project,
|
||||
mostly to do with dev, testing, CI and release gotchas, reminders
|
||||
and best practises.
|
||||
|
||||
``tractor`` is a fairly novel project compared to most since it is
|
||||
effectively a new way of doing distributed computing in Python and
|
||||
is much closer to working with an "application level runtime"
|
||||
(like erlang OTP or scala's akka project) than it is a traditional
|
||||
Python library. As such, having an arsenal of tools and recipes
|
||||
for figuring out the right way to debug problems when they do
|
||||
arise is somewhat of a necessity.
|
||||
|
||||
Making a release
|
||||
----------------
|
||||
|
||||
Nothing fancy: the traditional PyPA flow on the hatchling_ build
|
||||
backend, with uv_ doing the driving and towncrier_ generating the
|
||||
changelog.
|
||||
|
||||
1. collect news fragments: user-facing changes should land with a
|
||||
small ``.rst`` snippet under ``nooz/`` (see ``nooz/HOWTO.rst``;
|
||||
fragment types are ``feature``, ``bugfix``, ``doc`` and
|
||||
``trivial``),
|
||||
|
||||
2. render them into ``NEWS.rst``::
|
||||
|
||||
uvx towncrier build --version <version>
|
||||
|
||||
3. build and upload (testpypi first if you're being careful)::
|
||||
|
||||
uv build
|
||||
uvx twine upload -r testpypi dist/*
|
||||
uvx twine upload dist/*
|
||||
|
||||
How you organize built artifacts under ``dist/`` locally (per
|
||||
release sub-dirs and such) is entirely up to you.
|
||||
|
||||
Keep in mind that PyPi releases tend to lag the ``main`` branch
|
||||
since we develop in the open — ``main`` is usually the thing to
|
||||
run when you want the latest.
|
||||
|
||||
Debugging and monitoring actor trees
|
||||
------------------------------------
|
||||
|
||||
Your "what is my tree doing right now?" toolbox, in escalation
|
||||
order:
|
||||
|
||||
**Live process-tree view** — keep a ``watch``-ed ``pstree``
|
||||
running in a side terminal; actor procs are recognizable by their
|
||||
``_subactor[<name>@<uuid-prefix>]`` process titles. The exact
|
||||
one-liners (plus the ``pgrep`` marker recipes) live in
|
||||
:doc:`/guide/testing`.
|
||||
|
||||
**SIGUSR1 task-tree dumps** — boot any tree with
|
||||
``enable_stack_on_sig=True`` (or export
|
||||
``TRACTOR_ENABLE_STACKSCOPE=1``) and every actor installs a
|
||||
stackscope_ signal handler. Then from any shell::
|
||||
|
||||
# dump every actor's live trio task tree:
|
||||
pkill --signal SIGUSR1 -f <part-of-your-cmd>
|
||||
|
||||
# or for a single process:
|
||||
kill -SIGUSR1 $(pgrep -f <part-of-your-cmd>)
|
||||
|
||||
Each dump is also tee'd (append-mode) to
|
||||
``/tmp/tractor-stackscope-<pid>.log`` so you still get output
|
||||
under pytest capture or in CI. This works *without* debug-mode
|
||||
being enabled — it's the lightest-weight hang-investigation tool
|
||||
in the box.
|
||||
|
||||
**The built-in multi-process debugger** — ``debug_mode=True``
|
||||
plus :func:`tractor.pause` and friends: the heavyweight champ for
|
||||
interactive, REPL-driven inspection of a whole tree (including
|
||||
crash handling). Remember pytest capture interplay — see
|
||||
:doc:`/guide/testing`.
|
||||
|
||||
**Post-mortem zombie sweeps** — ``scripts/tractor-reap`` for the
|
||||
(should-be-rare!) cases where hacking on the runtime itself wedges
|
||||
a tree: a SIGINT-first, structured concurrency (SC) polite
|
||||
escalation, plus ``--shm`` and ``--uds`` leaked-resource sweeps.
|
||||
|
||||
Using the log system to trace ``trio`` task flow
|
||||
------------------------------------------------
|
||||
|
||||
The logging system is oriented around the **stack "layers" of the
|
||||
runtime**, letting you trace logical abstraction layers in the
|
||||
code — errors, cancellation, IPC and streaming, the low level
|
||||
transport and wire protocols — independently of one another.
|
||||
|
||||
Concretely, ``tractor.log.get_logger()`` returns a
|
||||
``StackLevelAdapter`` sporting extra level-methods beyond the
|
||||
stdlib set, including:
|
||||
|
||||
- ``.cancel()`` — cancellation-machinery flow,
|
||||
|
||||
- ``.runtime()`` — actor-runtime lifecycle chatter,
|
||||
|
||||
- ``.devx()`` — debugger/devx tooling internals,
|
||||
|
||||
- ``.transport()`` — wire-level msging events.
|
||||
|
||||
To get console output at any level from your own code::
|
||||
|
||||
from tractor.log import get_console_log
|
||||
get_console_log('cancel')
|
||||
|
||||
or, runtime-wide without touching code, just export
|
||||
``TRACTOR_LOGLEVEL=cancel`` (the env-var wins over caller-passed
|
||||
levels; great for test runs).
|
||||
|
||||
When you want only *one subsystem* cranked, the suite's ``--tl``
|
||||
flag (and ``tractor.log.apply_logspec()``) accept a per-sublogger
|
||||
spec::
|
||||
|
||||
uv run pytest tests/... --tl 'devx:runtime,trionics:cancel'
|
||||
|
||||
Every record's header includes the emitting actor and task names,
|
||||
so cross-process flows can be stitched back together by eyeball
|
||||
(or grep).
|
||||
|
||||
.. seealso::
|
||||
- :doc:`/guide/testing` — running the suite, watching trees
|
||||
live, examples-as-tests conventions and the zombie-reaper.
|
||||
- :doc:`/guide/discovery` — the registrar mechanics you'll
|
||||
bump into when running multiple trees on one host.
|
||||
|
||||
.. _hatchling: https://hatch.pypa.io/latest/
|
||||
.. _uv: https://docs.astral.sh/uv/
|
||||
.. _towncrier: https://towncrier.readthedocs.io/en/stable/
|
||||
.. _stackscope: https://github.com/oremanj/stackscope
|
||||
|
|
@ -0,0 +1,60 @@
|
|||
Project
|
||||
=======
|
||||
Everything meta: where the project's been (the
|
||||
:doc:`changelog`), where it's going (the roadmap below),
|
||||
how to hack on it (:doc:`dev-tips` and
|
||||
:doc:`/guide/testing`) and where to find the humans.
|
||||
|
||||
.. toctree::
|
||||
:maxdepth: 1
|
||||
|
||||
changelog
|
||||
dev-tips
|
||||
|
||||
What the future holds
|
||||
---------------------
|
||||
Help us push toward the future of distributed Python!
|
||||
Planned (or dreamed of) work non-comprehensively
|
||||
includes,
|
||||
|
||||
- Erlang-style supervisors via composed context
|
||||
managers (see `#22`_),
|
||||
- typed capability-based (dialog) protocols, ie.
|
||||
evolving our `msg-spec`_ system into per-dialog
|
||||
contracts (see `#196`_ with draft work in `#311`_),
|
||||
- a higher level "service manager" API for daemon
|
||||
lifetime mgmt over actor trees (in the works on an
|
||||
experimental branch as ``tractor.hilevel``),
|
||||
- richer `discovery`_ via gossip and/or
|
||||
`rendezvous protocol`_ approaches (today's registrar
|
||||
is intentionally naive),
|
||||
- more IPC transports: the current ``tcp`` | ``uds``
|
||||
pair wants friends (QUIC, shm-ring-buffers, RUDP,
|
||||
wireguard tunnels),
|
||||
- an extensive `chaos engineering`_ test suite,
|
||||
- a respawn-from-REPL system for crashed (sub-)actors.
|
||||
|
||||
Feel like saying hi?
|
||||
--------------------
|
||||
This project is very much coupled to the ongoing
|
||||
development of ``trio`` (i.e. ``tractor`` gets most of
|
||||
its ideas from that brilliant community). If you want
|
||||
to help, have suggestions or just want to say hi,
|
||||
please feel free to reach us in our `matrix channel`_.
|
||||
If matrix seems too hip, we're also mostly all in the
|
||||
`trio gitter channel`_!
|
||||
|
||||
Contributions of all kinds welcome: docs, examples,
|
||||
bug reports, new transports, supervisor strategies,
|
||||
philosophical debates about what an "actor model"
|
||||
really is B)
|
||||
|
||||
.. _#22: https://github.com/goodboy/tractor/issues/22
|
||||
.. _#196: https://github.com/goodboy/tractor/issues/196
|
||||
.. _#311: https://github.com/goodboy/tractor/pull/311
|
||||
.. _msg-spec: https://jcristharif.com/msgspec/
|
||||
.. _discovery: https://zguide.zeromq.org/docs/chapter8/#Discovery
|
||||
.. _rendezvous protocol: https://en.wikipedia.org/wiki/Rendezvous_protocol
|
||||
.. _chaos engineering: https://principlesofchaos.org/
|
||||
.. _matrix channel: https://matrix.to/#/!tractor:matrix.org
|
||||
.. _trio gitter channel: https://gitter.im/python-trio/general
|
||||
|
|
@ -0,0 +1,36 @@
|
|||
Getting started
|
||||
===============
|
||||
Welcome aboard B)
|
||||
|
||||
Real talk before any code: the first step to grok ``tractor`` is
|
||||
to get an intermediate knowledge of ``trio`` and **structured
|
||||
concurrency** (SC). ``tractor`` **is just** ``trio`` - but with
|
||||
nurseries for process management and cancel-able streaming IPC -
|
||||
so every rule you already know about task lifetimes, cancellation
|
||||
and error propagation keeps holding, just now across process (and
|
||||
host!) boundaries. Some great places to start are,
|
||||
|
||||
- the seminal `blog post`_,
|
||||
- obviously the `trio docs`_,
|
||||
- wikipedia's nascent SC_ page,
|
||||
- the fancy diagrams @ libdill-docs_.
|
||||
|
||||
Once you've taken in (some of) the canon, get installed and go
|
||||
spawn your first actor tree:
|
||||
|
||||
.. toctree::
|
||||
:maxdepth: 1
|
||||
|
||||
install
|
||||
quickstart
|
||||
|
||||
.. seealso::
|
||||
|
||||
Already installed and itching? Jump straight to
|
||||
:doc:`/start/quickstart`; once you're through the on-ramp the
|
||||
:doc:`guide pages </guide/index>` take each subsystem deeper.
|
||||
|
||||
.. _blog post: https://vorpus.org/blog/notes-on-structured-concurrency-or-go-statement-considered-harmful/
|
||||
.. _trio docs: https://trio.readthedocs.io/en/latest/
|
||||
.. _SC: https://en.wikipedia.org/wiki/Structured_concurrency
|
||||
.. _libdill-docs: https://sustrik.github.io/libdill/structured-concurrency.html
|
||||
|
|
@ -0,0 +1,75 @@
|
|||
Install
|
||||
=======
|
||||
``tractor`` is still in an *alpha-near-beta-stage* for many of
|
||||
its subsystems, however we are very close to having a stable
|
||||
lowlevel runtime and API. Expect the occasional rough edge (and
|
||||
feel free to report it!).
|
||||
|
||||
Supported platforms
|
||||
-------------------
|
||||
- **python**: ``>=3.13,<3.15`` - yes, we ride near the front of
|
||||
the release train; 3.14 additionally unlocks the experimental
|
||||
PEP-734 sub-interpreter spawn backend,
|
||||
- **linux**: the primary development and CI platform,
|
||||
- **macos**: officially supported,
|
||||
- **windows**: currently *untested* - we disabled CI-testing on
|
||||
windows a while back and haven't had the cycles to revive it.
|
||||
It mostly worked historically; if you're a windows person we'd
|
||||
love a hand getting it back in the test matrix.
|
||||
|
||||
With ``uv`` (preferred)
|
||||
-----------------------
|
||||
We use the very hip uv_ for project mgmt and recommend you do
|
||||
too. Add ``tractor`` to your project::
|
||||
|
||||
uv add tractor
|
||||
|
||||
or, since the git ``main`` branch is often much further ahead
|
||||
than any latest release (see the PyPi note below), track ``main``
|
||||
directly::
|
||||
|
||||
uv add "tractor @ git+https://github.com/goodboy/tractor.git"
|
||||
|
||||
From PyPi
|
||||
---------
|
||||
We ofc also offer "releases" on PyPi_::
|
||||
|
||||
pip install tractor
|
||||
|
||||
Just note that **YMMV** since ``main`` is usually well ahead of
|
||||
the latest published alpha; when in doubt go with a git install
|
||||
as per above (or hack from source as per below).
|
||||
|
||||
From source
|
||||
-----------
|
||||
To run the bundled examples in-tree, or to start hacking on the
|
||||
code base, clone and sync a dev env::
|
||||
|
||||
git clone https://github.com/goodboy/tractor.git
|
||||
cd tractor
|
||||
uv sync --dev
|
||||
uv run python examples/rpc_bidir_streaming.py
|
||||
|
||||
Consider activating a virtual/project-env before starting to hack
|
||||
on the code base::
|
||||
|
||||
# you could use plain ol' venvs
|
||||
# https://docs.astral.sh/uv/pip/environments/
|
||||
uv venv tractor_py313 --python 3.13
|
||||
|
||||
# but @goodboy prefers the more explicit (and shell agnostic)
|
||||
# https://docs.astral.sh/uv/configuration/environment/#uv_project_environment
|
||||
UV_PROJECT_ENVIRONMENT="tractor_py313"
|
||||
|
||||
# hint hint, enter @goodboy's fave shell B)
|
||||
uv run --dev xonsh
|
||||
|
||||
.. seealso::
|
||||
|
||||
All set? Go boot a process tree in :doc:`/start/quickstart`.
|
||||
And if the install fights you, swing by the `matrix channel`_
|
||||
and we'll sort it out.
|
||||
|
||||
.. _uv: https://docs.astral.sh/uv/
|
||||
.. _PyPi: https://pypi.org/project/tractor/
|
||||
.. _matrix channel: https://matrix.to/#/!tractor:matrix.org
|
||||
|
|
@ -0,0 +1,264 @@
|
|||
Quickstart
|
||||
==========
|
||||
Time to spawn something B)
|
||||
|
||||
If you take one thing from this page make it this: ``tractor``
|
||||
**is just** ``trio`` - but with nurseries for process management
|
||||
and cancel-able streaming IPC. Every "*actor*" you'll meet below
|
||||
is a plain Python **process** running its own ``trio.run()``
|
||||
scheduled task tree, linked back to its parent through an IPC
|
||||
protocol which keeps the whole tree `structured concurrency`_
|
||||
(SC) compliant end-to-end. If you know your nursery_ semantics
|
||||
you already know most of ``tractor``; we just stretch them across
|
||||
the process boundary.
|
||||
|
||||
.. d2:: diagrams/actor_tree.d2
|
||||
:alt: a supervision tree of actor processes
|
||||
:margin:
|
||||
:caption: every arrow is a parent which **must wait** on its kids
|
||||
|
||||
Your first actor tree
|
||||
---------------------
|
||||
``trio`` takes the hard-line position that a parent task **must
|
||||
wait** on the children it spawns; causality_ is paramount! So
|
||||
does ``tractor``, one abstraction layer up:
|
||||
``tractor.open_nursery()`` yields an ``ActorNursery`` which
|
||||
**must** wait on its spawned *subactors* to complete (or error)
|
||||
before the ``async with`` block exits, in the same causal_ way a
|
||||
``trio`` nursery waits on its subtasks. That includes any one
|
||||
child's crash cancelling all of its siblings: *one-cancels-all*
|
||||
supervision, `exactly like trio`_.
|
||||
|
||||
Enough preamble, spawn a process:
|
||||
|
||||
.. literalinclude:: ../../examples/actor_spawning_and_causality.py
|
||||
:caption: examples/actor_spawning_and_causality.py
|
||||
:language: python
|
||||
|
||||
Run it::
|
||||
|
||||
$ python examples/actor_spawning_and_causality.py
|
||||
Dang that's beautiful
|
||||
|
||||
What's going on here?
|
||||
|
||||
- ``trio.run(main)`` starts the **root actor**; the ``tractor``
|
||||
runtime boots *implicitly* inside ``tractor.open_nursery()``
|
||||
whenever it isn't already up. No special entrypoint, no
|
||||
framework takeover - it's just a ``trio`` app,
|
||||
- inside ``main()`` a *subactor* is spawned via
|
||||
``ActorNursery.run_in_actor()`` and told to run exactly one
|
||||
function: ``cellar_door()``,
|
||||
- you get back a ``Portal``: your handle for invoking tasks in
|
||||
the new process's (separate!) memory domain. We lean on it
|
||||
much harder in the next section,
|
||||
- the subactor, *some_linguist*, boots a fresh ``trio.run()`` in
|
||||
a **new process** and executes ``cellar_door()`` as its *main
|
||||
task* (note the child proving it is *not* the root with
|
||||
``tractor.is_root_process()``), then ships the return value
|
||||
back over IPC,
|
||||
- the parent grabs that *final result* with
|
||||
``await portal.wait_for_result()``, much like you'd expect
|
||||
from a "future" - except causality is preserved: the nursery
|
||||
block only exits once the child is *done*, dead, and reaped.
|
||||
|
||||
.. margin:: Just need a worker pool?
|
||||
|
||||
If all you want is to throw *sync* functions at your cores,
|
||||
also check out trio-parallel_. ``tractor`` is aimed at
|
||||
structured, (possibly) distributed *trees* of cooperating
|
||||
``trio`` programs; a worker pool is a trivial special case.
|
||||
|
||||
.. note::
|
||||
|
||||
``run_in_actor()`` is the *convenience* wrapper: one-shot
|
||||
spawn-run-reap semantics for when a subactor's entire job is
|
||||
a single function call. The core primitives are
|
||||
``ActorNursery.start_actor()`` (next up) paired with
|
||||
``Portal.open_context()`` for full, SC-linked cross-actor
|
||||
dialogs - see :doc:`/guide/context`.
|
||||
|
||||
Daemon actors and RPC
|
||||
---------------------
|
||||
A ``run_in_actor()``-spawned actor terminates when its main task
|
||||
returns. But often you want long-lived *daemon* actors instead:
|
||||
spawned once, then serving (allowlisted) RPC requests until told
|
||||
otherwise. That's ``start_actor()``:
|
||||
|
||||
.. literalinclude:: ../../examples/actor_spawning_and_causality_with_daemon.py
|
||||
:caption: examples/actor_spawning_and_causality_with_daemon.py
|
||||
:language: python
|
||||
|
||||
Two lifetime rules to internalize:
|
||||
|
||||
- a ``run_in_actor()`` actor lives exactly as long as its main
|
||||
task; the nursery waits for that function (and thus the
|
||||
process) to complete before unblocking,
|
||||
- a ``start_actor()`` actor *lives forever* - an RPC daemon the
|
||||
nursery will happily wait on **indefinitely** - until some
|
||||
task explicitly cancels it via ``Portal.cancel_actor()`` (as
|
||||
above), or its parent nursery is cancelled wholesale.
|
||||
|
||||
.. tip::
|
||||
|
||||
Want your *entire program* to just be a long-lived RPC
|
||||
daemon? ``tractor.run_daemon()`` is the blocking shorthand:
|
||||
it ``trio.run()``\s a root actor which serves requests until
|
||||
cancelled.
|
||||
|
||||
The ``enable_modules=[__name__]`` kwarg is the other thing to
|
||||
notice: it lists the module paths the subactor will load and
|
||||
*expose* for remote invocation.
|
||||
``await portal.run(movie_theatre_question)`` works because this
|
||||
very module is in that allowlist (and note we call it twice; the
|
||||
daemon happily serves repeat requests). Ask for a function from
|
||||
any module *not* enabled and you're denied with a
|
||||
``ModuleNotExposed`` error: a simple, capability-style
|
||||
restriction mechanism built on Python's own module system.
|
||||
|
||||
We are *processes*
|
||||
------------------
|
||||
Why processes (and not, say, threads)? Python has a GIL and an
|
||||
`actor model`_ by definition shares **nothing** between its
|
||||
concurrent units, so real OS processes are the natural fit: you
|
||||
get all your cores locally, and since actors only ever talk via
|
||||
IPC, the exact same code distributes over multiple hosts without
|
||||
modification.
|
||||
|
||||
Of course, the moment you hear "process trees" you should be
|
||||
asking: *what about zombies?* Watch ``tractor`` eat one for
|
||||
breakfast - run this while monitoring your process tree::
|
||||
|
||||
$TERM -e watch -n 0.1 "pstree -a $$" \
|
||||
& python examples/parallelism/we_are_processes.py \
|
||||
&& kill $!
|
||||
|
||||
.. literalinclude:: ../../examples/parallelism/we_are_processes.py
|
||||
:caption: examples/parallelism/we_are_processes.py
|
||||
:language: python
|
||||
|
||||
.. margin:: Who's who in ``pstree``?
|
||||
|
||||
Every subactor (best-effort, via the optional
|
||||
``setproctitle`` dep) re-titles its OS process like
|
||||
``_subactor[worker_0@<uuid>]``, so ``pstree``/``htop``/
|
||||
``pgrep -f`` can tell your actors apart at a glance.
|
||||
|
||||
You'll see something like::
|
||||
|
||||
$ python examples/parallelism/we_are_processes.py
|
||||
Yo, i'm 'worker_2' running in pid 1777246
|
||||
Yo, i'm 'worker_0' running in pid 1777244
|
||||
Yo, i'm 'worker_3' running in pid 1777247
|
||||
Yo, i'm 'worker_1' running in pid 1777245
|
||||
This process tree will self-destruct in 1 sec...
|
||||
Zombies Contained
|
||||
|
||||
(The worker lines land in whatever order the OS schedules them;
|
||||
they're separate *processes*, racing, and that's the point.)
|
||||
|
||||
An actor is spawned per core, each parks itself in
|
||||
``trio.sleep_forever()``... and then the root *crashes on
|
||||
purpose*. The ``ActorNursery`` responds with hard ``trio``
|
||||
discipline: every child is cancelled, every process is reaped,
|
||||
the error propagates to ``trio.run()``, and your terminal prints
|
||||
``Zombies Contained``. No orphans, no ``kill -9`` archaeology in
|
||||
``htop`` afterwards.
|
||||
|
||||
.. note::
|
||||
|
||||
**The zombie-safety guarantee**: ``tractor`` tries to protect
|
||||
you from zombies, *no matter what*. If you can create zombie
|
||||
child processes (without using a system signal) it **is a
|
||||
bug** - please report it so we can hunt it down.
|
||||
|
||||
A trynamic first scene
|
||||
----------------------
|
||||
So far the root actor has done all the talking, but subactors
|
||||
can just as well discover and call *each other*. Let's direct a
|
||||
couple actors and have them run their lines for the hip new film
|
||||
we're shooting:
|
||||
|
||||
.. literalinclude:: ../../examples/a_trynamic_first_scene.py
|
||||
:caption: examples/a_trynamic_first_scene.py
|
||||
:language: python
|
||||
|
||||
The script of the scene (runtime ``INFO`` log lines trimmed)::
|
||||
|
||||
$ python examples/a_trynamic_first_scene.py
|
||||
Alright... Action!
|
||||
Hi my name is gretchen
|
||||
Hi my name is donny
|
||||
CUTTTT CUUTT CUT!!! Donny!! You're supposed to say...
|
||||
|
||||
The new tricks in play:
|
||||
|
||||
- two subactors, *donny* and *gretchen*, are each told to run
|
||||
``say_hello()`` targeting the *other* by name,
|
||||
- ``tractor.wait_for_actor()`` blocks until the named peer has
|
||||
registered with the tree's *registrar* (every actor announces
|
||||
itself at boot), then yields a ``Portal`` connected
|
||||
**directly** to that peer,
|
||||
- each actor invokes its partner's ``hi()`` over that portal:
|
||||
actor-to-actor RPC with the root merely *directing* - and both
|
||||
final lines flow back to ``main()`` via
|
||||
``await portal.wait_for_result()``,
|
||||
- ``tractor.log.get_console_log("INFO")`` cranks up runtime
|
||||
logging so you can watch the spawn/register/cancel machinery
|
||||
narrate itself; remove it for a quiet set.
|
||||
|
||||
Cross-actor calls look just like (async) function calls; there
|
||||
are no proxy objects and no shared references, only messages B)
|
||||
|
||||
Crash handling, native feeling
|
||||
------------------------------
|
||||
One last teaser before the guide proper. Flip exactly one
|
||||
switch:
|
||||
|
||||
.. code:: python
|
||||
|
||||
async with tractor.open_nursery(
|
||||
debug_mode=True,
|
||||
) as an:
|
||||
...
|
||||
|
||||
and any crash, in *any* actor at *any* depth of the tree, drops
|
||||
your terminal into a multi-process-safe pdbp_ REPL at the
|
||||
offending frame, with the rest of the tree held back from
|
||||
clobbering the tty. ``await tractor.pause()`` likewise gives you
|
||||
a breakpoint that *just works* inside subprocesses. We think it
|
||||
might be the first native multi-process debugging UX for Python;
|
||||
get the full tour in :doc:`/guide/debugging`.
|
||||
|
||||
Where to next?
|
||||
--------------
|
||||
You can now boot a runtime, spawn one-shot and daemon actors,
|
||||
make cross-process RPC calls, and contain zombies: that's the
|
||||
on-ramp done. The guide takes each subsystem deeper,
|
||||
|
||||
- :doc:`/explain/sc-distributed` - the structured concurrency
|
||||
worldview and how ``tractor`` extends it across processes,
|
||||
- :doc:`/guide/spawning` - everything ``ActorNursery``: spawn
|
||||
kwargs, lifetimes and supervision semantics,
|
||||
- :doc:`/guide/rpc` - the ``Portal`` in depth: calling into
|
||||
another actor's memory domain,
|
||||
- :doc:`/guide/context` - the core API: ``@tractor.context``
|
||||
endpoints, the ``ctx.started()`` handshake, and SC-linked
|
||||
cross-actor task pairs,
|
||||
- :doc:`/guide/streaming` - bidirectional ``MsgStream`` dialogs
|
||||
and fan-out broadcasting,
|
||||
- :doc:`/guide/debugging` - the multi-process REPL, crash
|
||||
handling mode, and ``tractor.pause()``,
|
||||
- :doc:`/guide/asyncio` - "infected ``asyncio``" mode: SC
|
||||
supervision wrapped around ``asyncio`` tasks,
|
||||
- :doc:`/guide/discovery` - registries, service daemons, and
|
||||
finding actors from anywhere in (or out of) the tree.
|
||||
|
||||
.. _structured concurrency: https://en.wikipedia.org/wiki/Structured_concurrency
|
||||
.. _nursery: https://trio.readthedocs.io/en/latest/reference-core.html#nurseries-and-spawning
|
||||
.. _causality: https://vorpus.org/blog/some-thoughts-on-asynchronous-api-design-in-a-post-asyncawait-world/#c-c-c-c-causality-breaker
|
||||
.. _causal: https://vorpus.org/blog/some-thoughts-on-asynchronous-api-design-in-a-post-asyncawait-world/#causality
|
||||
.. _exactly like trio: https://trio.readthedocs.io/en/latest/reference-core.html#cancellation-semantics
|
||||
.. _actor model: https://en.wikipedia.org/wiki/Actor_model
|
||||
.. _trio-parallel: https://github.com/richardsheridan/trio-parallel
|
||||
.. _pdbp: https://github.com/mdmintz/pdbp
|
||||
Loading…
Reference in New Issue