tractor/NEWS.rst

=========
Changelog
=========

.. towncrier release notes start

tractor 0.1.0a3 (2021-11-02)
============================

Features
--------

- Switch to using the ``trio`` process spawner by default on windows. (#166)

  This gets windows users debugger support (manually tested) and in
  general a more resilient (nested) actor tree implementation.

- Add optional `msgspec <https://jcristharif.com/msgspec/>`_ support
  as an alernative, faster MessagePack codec. (#214)

  Provides us with a path toward supporting typed IPC message contracts. Further,
  ``msgspec`` structs may be a valid tool to start for formalizing our
  "SC dialog un-protocol" messages as described in `#36
  <https://github.com/goodboy/tractor/issues/36>`_`.

- Introduce a new ``tractor.trionics`` `sub-package`_ that exposes
  a selection of our relevant high(er) level trio primitives and
  goodies. (#241)

  At outset we offer a ``gather_contexts()`` context manager for
  concurrently entering a sequence of async context managers (much like
  a version of ``asyncio.gather()`` but for context managers) and use it
  in a new ``tractor.open_actor_cluster()`` manager-helper that can be
  entered to concurrently spawn a flat actor pool. We also now publicly
  expose our "broadcast channel" APIs (``open_broadcast_receiver()``)
  from here.

.. _sub-package: ../tractor/trionics

- Change the core message loop to handle task and actor-runtime cancel
  requests immediately instead of scheduling them as is done for rpc-task
  requests. (#245)

  In order to obtain more reliable teardown mechanics for (complex) actor
  trees it's important that we specially treat cancel requests as having
  higher priority. Previously, it was possible that task cancel requests
  could actually also themselves be cancelled if a "actor-runtime" cancel
  request was received (can happen during messy multi actor crashes that
  propagate). Instead cancels now block the msg loop until serviced and
  a response is relayed back to the requester. This also allows for
  improved debugger support since we have determinism guarantees about
  which processes must wait before hard killing their children.

- Drop Python 3.8 support in favor of rolling with two latest releases
  for the time being. (#248)


tractor 0.1.0a2 (2021-09-07)
============================

Features
--------

- Add `tokio-style broadcast channels
  <https://docs.rs/tokio/1.11.0/tokio/sync/broadcast/index.html>`_ as
  a solution for `#204 <https://github.com/goodboy/tractor/pull/204>`_ and
  discussed thoroughly in `trio/#987
  <https://github.com/python-trio/trio/issues/987>`_.

  This gives us local task broadcast functionality using a new
  ``BroadcastReceiver`` type which can wrap ``trio.ReceiveChannel``  and
  provide fan-out copies of a stream of data to every subscribed consumer.
  We use this new machinery to provide a ``ReceiveMsgStream.subscribe()``
  async context manager which can be used by actor-local concumers tasks
  to easily pull from a shared and dynamic IPC stream. (`#229
  <https://github.com/goodboy/tractor/pull/229>`_)


Bugfixes
--------

- Handle broken channel/stream faults where the root's tty lock is left
  acquired by some child actor who went MIA and the root ends up hanging
  indefinitely. (`#234 <https://github.com/goodboy/tractor/pull/234>`_)

  There's two parts here: we no longer shield wait on the lock and,
  now always do our best to release the lock on the expected worst
  case connection faults.


Deprecations and Removals
-------------------------

- Drop stream "shielding" support which was originally added to sidestep
  a cancelled call to ``.receive()``

  In the original api design a stream instance was returned directly from
  a call to ``Portal.run()`` and thus there was no "exit phase" to handle
  cancellations and errors which would trigger implicit closure. Now that
  we have said enter/exit semantics with ``Portal.open_stream_from()`` and
  ``Context.open_stream()`` we can drop this implicit (and arguably
  confusing) behavior. (`#230 <https://github.com/goodboy/tractor/pull/230>`_)

- Drop Python 3.7 support in preparation for supporting 3.9+ syntax.
  (`#232 <https://github.com/goodboy/tractor/pull/232>`_)


tractor 0.1.0a1 (2021-08-01)
============================

Features
--------
- Updated our uni-directional streaming API (`#206
  <https://github.com/goodboy/tractor/pull/206>`_) to require a context
  manager style ``async with Portal.open_stream_from(target) as stream:``
  which explicitly determines when to stop a stream in the calling (aka
  portal opening) actor much like ``async_generator.aclosing()``
  enforcement.

- Improved the ``multiprocessing`` backend sub-actor reaping (`#208
  <https://github.com/goodboy/tractor/pull/208>`_) during actor nursery
  exit, particularly during cancellation scenarios that previously might
  result in hard to debug hangs.

- Added initial bi-directional streaming support in `#219
  <https://github.com/goodboy/tractor/pull/219>`_ with follow up debugger
  improvements via `#220 <https://github.com/goodboy/tractor/pull/220>`_
  using the new ``tractor.Context`` cross-actor task syncing system.
  The debugger upgrades add an edge triggered last-in-tty-lock semaphore
  which allows the root process for a tree to avoid clobbering children
  who have queued to acquire the ``pdb`` repl by waiting to cancel
  sub-actors until the lock is known to be released **and** has no
  pending waiters.


Experiments and WIPs
--------------------
- Initial optional ``msgspec`` serialization support in `#214
  <https://github.com/goodboy/tractor/pull/214>`_ which should hopefully
  land by next release.

- Improved "infect ``asyncio``" cross-loop task cancellation and error
  propagation by vastly simplifying the cross-loop-task streaming approach. 
  We may end up just going with a use of ``anyio`` in the medium term to
  avoid re-doing work done by their cross-event-loop portals.  See the
  ``infect_asyncio`` for details.


Improved Documentation
----------------------
- `Updated our readme <https://github.com/goodboy/tractor/pull/211>`_ to
  include more (and better) `examples
  <https://github.com/goodboy/tractor#run-a-func-in-a-process>`_ (with
  matching multi-terminal process monitoring shell commands) as well as
  added many more examples to the `repo set
  <https://github.com/goodboy/tractor/tree/master/examples>`_.

- Added a readme `"actors under the hood" section
  <https://github.com/goodboy/tractor#under-the-hood>`_ in an effort to
  guard against suggestions for changing the API away from ``trio``'s
  *tasks-as-functions* style.

- Moved to using the `sphinx book theme
  <https://sphinx-book-theme.readthedocs.io/en/latest/index.html>`_
  though it needs some heavy tweaking and doesn't seem to show our logo
  on rtd :(


Trivial/Internal Changes
------------------------
- Added a new ``TransportClosed`` internal exception/signal (`#215
  <https://github.com/goodboy/tractor/pull/215>`_ for catching TCP
  channel gentle closes instead of silently falling through the message
  handler loop via an async generator ``return``.


Deprecations and Removals
-------------------------
- Dropped support for invoking sync functions (`#205
  <https://github.com/goodboy/tractor/pull/205>`_) in other
  actors/processes since you can always wrap a sync function from an
  async one.  Users can instead consider using ``trio-parallel`` which
  is a project specifically geared for purely synchronous calls in
  sub-processes.

- Deprecated our ``tractor.run()`` entrypoint `#197
  <https://github.com/goodboy/tractor/pull/197>`_; the runtime is now
  either started implicitly in first actor nursery use or via an
  explicit call to ``tractor.open_root_actor()``. Full removal of
  ``tractor.run()`` will come by beta release.


tractor 0.1.0a0 (2021-02-28)
============================

..
    TODO: fill out more of the details of the initial feature set in some TLDR form

Summary
-------
- ``trio`` based process spawner (using ``subprocess``)
- initial multi-process debugging with ``pdb++``
- windows support using both ``trio`` and ``multiprocessing`` spawners
- "portal" api for cross-process, structured concurrent, (streaming) IPC