305 lines
9.0 KiB
ReStructuredText
305 lines
9.0 KiB
ReStructuredText
|logo| ``tractor``: next-gen Python parallelism
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.. _actor model: https://en.wikipedia.org/wiki/Actor_model
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.. _trio: https://github.com/python-trio/trio
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.. _multi-processing: https://en.wikipedia.org/wiki/Multiprocessing
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.. _trionic: https://trio.readthedocs.io/en/latest/design.html#high-level-design-principles
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.. _async sandwich: https://trio.readthedocs.io/en/latest/tutorial.html#async-sandwich
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.. _structured concurrent: https://trio.discourse.group/t/concise-definition-of-structured-concurrency/228
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``tractor`` is a `structured concurrent`_ "`actor model`_" built on trio_ and multi-processing_.
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We pair structured concurrency and true multi-core parallelism with
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the aim of being the multi-processing framework *you always wanted*.
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The first step to grok ``tractor`` is to get the basics of ``trio`` down.
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A great place to start is the `trio docs`_ and this `blog post`_.
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Features
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--------
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- **It's just** a ``trio`` API
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- Infinitely nesteable process trees
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- Built-in APIs for inter-process streaming
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- A (first ever?) "native" multi-core debugger for Python using `pdb++`_
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- Support for multiple process spawning backends
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- A modular transport layer, allowing for custom serialization,
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communications protocols, and environment specific IPC primitives
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Run a func in a process
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-----------------------
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Use ``trio``'s style of focussing on *tasks as functions*:
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.. code:: python
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"""
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Run with a process monitor from a terminal using::
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$TERM -e watch -n 0.1 "pstree -a $$" \
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& python examples/parallelism/single_func.py \
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&& kill $!
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"""
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import os
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import tractor
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import trio
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async def burn_cpu():
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pid = os.getpid()
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# burn a core @ ~ 50kHz
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for _ in range(50000):
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await trio.sleep(1/50000/50)
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return os.getpid()
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async def main():
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async with tractor.open_nursery() as n:
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portal = await n.run_in_actor(burn_cpu)
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# burn rubber in the parent too
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await burn_cpu()
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# wait on result from target function
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pid = await portal.result()
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# end of nursery block
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print(f"Collected subproc {pid}")
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if __name__ == '__main__':
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trio.run(main)
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This runs ``burn_cpu()`` in a new process and reaps it on completion
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of the nursery block.
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If you only need to run a sync function and retreive a single result, you
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might want to check out `trio-parallel`_.
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Zombie safe: self-destruct a process tree
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-----------------------------------------
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``tractor`` tries to protect you from zombies, no matter what.
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.. code:: python
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"""
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Run with a process monitor from a terminal using::
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$TERM -e watch -n 0.1 "pstree -a $$" \
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& python examples/parallelism/we_are_processes.py \
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&& kill $!
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"""
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from multiprocessing import cpu_count
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import os
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import tractor
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import trio
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async def target():
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print(
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f"Yo, i'm '{tractor.current_actor().name}' "
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f"running in pid {os.getpid()}"
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)
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await trio.sleep_forever()
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async def main():
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async with tractor.open_nursery() as n:
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for i in range(cpu_count()):
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await n.run_in_actor(target, name=f'worker_{i}')
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print('This process tree will self-destruct in 1 sec...')
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await trio.sleep(1)
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# you could have done this yourself
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raise Exception('Self Destructed')
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if __name__ == '__main__':
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try:
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trio.run(main)
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except Exception:
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print('Zombies Contained')
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If you can create zombie child processes (without using a system signal)
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it **is a bug**.
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"Native" multi-process debugging
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--------------------------------
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Using the magic of `pdb++`_ and our internal IPC, we've
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been able to create a native feeling debugging experience for
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any (sub-)process in your ``tractor`` tree.
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.. code:: python
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from os import getpid
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import tractor
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import trio
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async def breakpoint_forever():
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"Indefinitely re-enter debugger in child actor."
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while True:
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yield 'yo'
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await tractor.breakpoint()
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async def name_error():
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"Raise a ``NameError``"
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getattr(doggypants)
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async def main():
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"""Test breakpoint in a streaming actor.
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"""
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async with tractor.open_nursery(
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debug_mode=True,
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loglevel='error',
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) as n:
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p0 = await n.start_actor('bp_forever', enable_modules=[__name__])
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p1 = await n.start_actor('name_error', enable_modules=[__name__])
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# retreive results
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stream = await p0.run(breakpoint_forever)
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await p1.run(name_error)
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if __name__ == '__main__':
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trio.run(main)
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You can run this with::
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>>> python examples/debugging/multi_daemon_subactors.py
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And, yes, there's a built-in crash handling mode B)
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We're hoping to add a respawn-from-repl system soon!
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Worker poolz are easy peasy
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---------------------------
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The initial ask from most new users is *"how do I make a worker
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pool thing?"*.
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``tractor`` is built to handle any SC (structured concurrent) process
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tree you can imagine; a "worker pool" pattern is a trivial special
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case.
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We have a `full worker pool re-implementation`_ of the std-lib's
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``concurrent.futures.ProcessPoolExecutor`` example for reference.
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You can run it like so (from this dir) to see the process tree in
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real time::
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$TERM -e watch -n 0.1 "pstree -a $$" \
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& python examples/parallelism/concurrent_actors_primes.py \
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&& kill $!
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This uses no extra threads, fancy semaphores or futures; all we need
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is ``tractor``'s IPC!
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.. _full worker pool re-implementation: https://github.com/goodboy/tractor/blob/master/examples/parallelism/concurrent_actors_primes.py
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Install
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-------
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From PyPi::
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pip install tractor
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From git::
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pip install git+git://github.com/goodboy/tractor.git
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Under the hood
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--------------
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``tractor`` is an attempt to pair trionic_ `structured concurrency`_ with
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distributed Python. You can think of it as a ``trio``
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*-across-processes* or simply as an opinionated replacement for the
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stdlib's ``multiprocessing`` but built on async programming primitives
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from the ground up.
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``tractor``'s nurseries let you spawn ``trio`` *"actors"*: new Python
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processes which each run a ``trio`` scheduled runtime - a call to ``trio.run()``.
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Don't be scared off by this description. ``tractor`` **is just** ``trio``
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but with nurseries for process management and cancel-able streaming IPC.
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If you understand how to work with ``trio``, ``tractor`` will give you
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the parallelism you've been missing.
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"Actors" communicate by exchanging asynchronous messages_ and avoid
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sharing state. The intention of this model is to allow for highly
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distributed software that, through the adherence to *structured
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concurrency*, results in systems which fail in predictable and
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recoverable ways.
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What's on the TODO:
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-------------------
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Help us push toward the future.
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- (Soon to land) ``asyncio`` support allowing for "infected" actors where
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`trio` drives the `asyncio` scheduler via the astounding "`guest mode`_"
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- Typed messaging protocols (ex. via ``msgspec``)
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- Erlang-style supervisors via composed context managers
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Feel like saying hi?
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--------------------
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This project is very much coupled to the ongoing development of
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``trio`` (i.e. ``tractor`` gets most of its ideas from that brilliant
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community). If you want to help, have suggestions or just want to
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say hi, please feel free to reach us in our `matrix channel`_. If
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matrix seems too hip, we're also mostly all in the the `trio gitter
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channel`_!
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.. _trio gitter channel: https://gitter.im/python-trio/general
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.. _matrix channel: https://matrix.to/#/!tractor:matrix.org
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.. _pdb++: https://github.com/pdbpp/pdbpp
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.. _guest mode: https://trio.readthedocs.io/en/stable/reference-lowlevel.html?highlight=guest%20mode#using-guest-mode-to-run-trio-on-top-of-other-event-loops
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.. _messages: https://en.wikipedia.org/wiki/Message_passing
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.. _trio docs: https://trio.readthedocs.io/en/latest/
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.. _blog post: https://vorpus.org/blog/notes-on-structured-concurrency-or-go-statement-considered-harmful/
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.. _structured concurrency: https://vorpus.org/blog/notes-on-structured-concurrency-or-go-statement-considered-harmful/
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.. _3 axioms: https://en.wikipedia.org/wiki/Actor_model#Fundamental_concepts
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.. _unrequirements: https://en.wikipedia.org/wiki/Actor_model#Direct_communication_and_asynchrony
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.. _async generators: https://www.python.org/dev/peps/pep-0525/
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.. _trio-parallel: https://github.com/richardsheridan/trio-parallel
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.. |gh_actions| image:: https://img.shields.io/endpoint.svg?url=https%3A%2F%2Factions-badge.atrox.dev%2Fgoodboy%2Ftractor%2Fbadge&style=popout-square
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:target: https://actions-badge.atrox.dev/goodboy/tractor/goto
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.. |docs| image:: https://readthedocs.org/projects/tractor/badge/?version=latest
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:target: https://tractor.readthedocs.io/en/latest/?badge=latest
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:alt: Documentation Status
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.. |logo| image:: _static/tractor_logo_side.svg
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:width: 250
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:align: middle
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