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=========
Changelog
=========
.. towncrier release notes start
tractor 0.1.0a4 (2021-12-18)
============================
Features
--------
- `#275 <https://github.com/goodboy/tractor/issues/275>`_: Re-license
code base under AGPLv3. Also see `#274
<https://github.com/goodboy/tractor/pull/274>`_ for majority
contributor consensus on this decision.
- `#121 <https://github.com/goodboy/tractor/issues/121>`_: Add
"infected ``asyncio`` mode; a sub-system to spawn and control
``asyncio`` actors using ``trio``'s guest-mode.
This gets us the following very interesting functionality:
- ability to spawn an actor that has a process entry point of
``asyncio.run()`` by passing ``infect_asyncio=True`` to
``Portal.start_actor()`` (and friends).
- the ``asyncio`` actor embeds ``trio`` using guest-mode and starts
a main ``trio`` task which runs the ``tractor.Actor._async_main()``
entry point engages all the normal ``tractor`` runtime IPC/messaging
machinery; for all purposes the actor is now running normally on
a ``trio.run()``.
- the actor can now make one-to-one task spawning requests to the
underlying ``asyncio`` event loop using either of:
* ``to_asyncio.run_task()`` to spawn and run an ``asyncio`` task to
completion and block until a return value is delivered.
* ``async with to_asyncio.open_channel_from():`` which spawns a task
and hands it a pair of "memory channels" to allow for bi-directional
streaming between the now SC-linked ``trio`` and ``asyncio`` tasks.
The output from any call(s) to ``asyncio`` can be handled as normal in
``trio``/``tractor`` task operation with the caveat of the overhead due
to guest-mode use.
For more details see the `original PR
<https://github.com/goodboy/tractor/pull/121>`_ and `issue
<https://github.com/goodboy/tractor/issues/120>`_.
- `#257 <https://github.com/goodboy/tractor/issues/257>`_: Add
``trionics.maybe_open_context()`` an actor-scoped async multi-task
context manager resource caching API.
Adds an SC-safe cacheing async context manager api that only enters on
the *first* task entry and only exits on the *last* task exit while in
between delivering the same cached value per input key. Keys can be
either an explicit ``key`` named arg provided by the user or a
hashable ``kwargs`` dict (will be converted to a ``list[tuple]``) which
is passed to the underlying manager function as input.
- `#261 <https://github.com/goodboy/tractor/issues/261>`_: Add
cross-actor-task ``Context`` oriented error relay, a new stream
overrun error-signal ``StreamOverrun``, and support disabling
``MsgStream`` backpressure as the default before a stream is opened or
by choice of the user.
We added stricter semantics around ``tractor.Context.open_stream():``
particularly to do with streams which are only opened at one end.
Previously, if only one end opened a stream there was no way for that
sender to know if msgs are being received until first, the feeder mem
chan on the receiver side hit a backpressure state and then that
condition delayed its msg loop processing task to eventually create
backpressure on the associated IPC transport. This is non-ideal in the
case where the receiver side never opened a stream by mistake since it
results in silent block of the sender and no adherence to the underlying
mem chan buffer size settings (which is still unsolved btw).
To solve this we add non-backpressure style message pushing inside
``Actor._push_result()`` by default and only use the backpressure
``trio.MemorySendChannel.send()`` call **iff** the local end of the
context has entered ``Context.open_stream():``. This way if the stream
was never opened but the mem chan is overrun, we relay back to the
sender a (new exception) ``SteamOverrun`` error which is raised in the
sender's scope with a special error message about the stream never
having been opened. Further, this behaviour (non-backpressure style
where senders can expect an error on overruns) can now be enabled with
``.open_stream(backpressure=False)`` and the underlying mem chan size
can be specified with a kwarg ``msg_buffer_size: int``.
Further bug fixes and enhancements in this changeset include:
- fix a race we were ignoring where if the callee task opened a context
it could enter ``Context.open_stream()`` before calling
``.started()``.
- Disallow calling ``Context.started()`` more then once.
- Enable ``Context`` linked tasks error relaying via the new
``Context._maybe_raise_from_remote_msg()`` which (for now) uses
a simple ``trio.Nursery.start_soon()`` to raise the error via closure
in the local scope.
- `#267 <https://github.com/goodboy/tractor/issues/267>`_: This
(finally) adds fully acknowledged remote cancellation messaging
support for both explicit ``Portal.cancel_actor()`` calls as well as
when there is a "runtime-wide" cancellations (eg. during KBI or
general actor nursery exception handling which causes a full actor
"crash"/termination).
You can think of this as the most ideal case in 2-generals where the
actor requesting the cancel of its child is able to always receive back
the ACK to that request. This leads to a more deterministic shutdown of
the child where the parent is able to wait for the child to fully
respond to the request. On a localhost setup, where the parent can
monitor the state of the child through process or other OS APIs instead
of solely through IPC messaging, the parent can know whether or not the
child decided to cancel with more certainty. In the case of separate
hosts, we still rely on a simple timeout approach until such a time
where we prefer to get "fancier".
- `#271 <https://github.com/goodboy/tractor/issues/271>`_: Add a per
actor ``debug_mode: bool`` control to our nursery.
This allows spawning actors via ``ActorNursery.start_actor()`` (and
other dependent methods) with a ``debug_mode=True`` flag much like
``tractor.open_nursery():`` such that per process crash handling
can be toggled for cases where a user does not need/want all child actors
to drop into the debugger on error. This is often useful when you have
actor-tasks which are expected to error often (and be re-run) but want
to specifically interact with some (problematic) child.
Bugfixes
--------
- `#239 <https://github.com/goodboy/tractor/issues/239>`_: Fix
keyboard interrupt handling in ``Portal.open_context()`` blocks.
Previously this was not triggering cancellation of the remote task
context and could result in hangs if a stream was also opened. This
fix is to accept `BaseException` since it is likely any other top
level exception other then KBI (even though not expected) should also
get this result.
- `#264 <https://github.com/goodboy/tractor/issues/264>`_: Fix
``Portal.run_in_actor()`` returns ``None`` result.
``None`` was being used as the cached result flag and obviously breaks
on a ``None`` returned from the remote target task. This would cause an
infinite hang if user code ever called ``Portal.result()`` *before* the
nursery exit. The simple fix is to use the *return message* as the
initial "no-result-received-yet" flag value and, once received, the
return value is read from the message to avoid the cache logic error.
- `#266 <https://github.com/goodboy/tractor/issues/266>`_: Fix
graceful cancellation of daemon actors
Previously, his was a bug where if the soft wait on a sub-process (the
``await .proc.wait()``) in the reaper task teardown was cancelled we
would fail over to the hard reaping sequence (meant for culling off any
potential zombies via system kill signals). The hard reap has a timeout
of 3s (currently though in theory we could make it shorter?) before
system signalling kicks in. This means that any daemon actor still
running during nursery exit would get hard reaped (3s later) instead of
cancelled via IPC message. Now we catch the ``trio.Cancelled``, call
``Portal.cancel_actor()`` on the daemon and expect the child to
self-terminate after the runtime cancels and shuts down the process.
- `#278 <https://github.com/goodboy/tractor/issues/278>`_: Repair
inter-actor stream closure semantics to work correctly with
``tractor.trionics.BroadcastReceiver`` task fan out usage.
A set of previously unknown bugs discovered in `#257
<https://github.com/goodboy/tractor/pull/257>`_ let graceful stream
closure result in hanging consumer tasks that use the broadcast APIs.
This adds better internal closure state tracking to the broadcast
receiver and message stream APIs and in particular ensures that when an
underlying stream/receive-channel (a broadcast receiver is receiving
from) is closed, all consumer tasks waiting on that underlying channel
are woken so they can receive the ``trio.EndOfChannel`` signal and
promptly terminate.
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.
- (`#248 <https://github.com/goodboy/tractor/pull/248>`_) Drop Python
3.8 support in favour of rolling with two latest releases for the time
being.
Misc
----
- (`#243 <https://github.com/goodboy/tractor/pull/243>`_) add a distinct
``'CANCEL'`` log level to allow the runtime to emit details about
cancellation machinery statuses.
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
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