tractor

The Python async-native multi-core system you always wanted.

https://actions-badge.atrox.dev/goodboy/tractor/goto https://tractor.readthedocs.io/en/latest/?badge=latest

tractor is a structured concurrent “actor model” built on trio and multi-processing.

It is an attempt to pair trionic structured concurrency with distributed Python. You can think of it as a trio -across-processes or simply as an opinionated replacement for the stdlib’s multiprocessing but built on async programming primitives from the ground up.

Don’t be scared off by this description. tractor is just ``trio`` but with nurseries for process management and cancel-able IPC. If you understand how to work with trio, tractor will give you the parallelism you’ve been missing.

tractor’s nurseries let you spawn trio “actors”: new Python processes which each run a trio scheduled task tree (also known as an async sandwich - a call to trio.run()). That is, each “Actor” is a new process plus a trio runtime.

“Actors” communicate by exchanging asynchronous messages and avoid sharing state. The intention of this model is to allow for highly distributed software that, through the adherence to structured concurrency, results in systems which fail in predictable and recoverable ways.

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.

Install

No PyPi release yet!

pip install git+git://github.com/goodboy/tractor.git

Alluring Features

• It’s just trio, but with SC applied to processes (aka

  “actors”)

• Infinitely nesteable process trees
• Built-in API for inter-process streaming

• A (first ever?) “native” multi-core debugger for Python using

  pdb++

• (Soon to land) asyncio support allowing for “infected” actors

  where trio drives the asyncio scheduler via the astounding “guest mode”

The example you’re probably after…

It seems the initial query from most new users is “how do I make a worker pool thing?”.

tractor is built to handle any SC process tree you can imagine; the “worker pool” pattern is a trivial special case:

# TODO: workerpool example

"""
Run with a process monitor from a terminal using:
$TERM -e watch -n 0.1  "pstree -a $$" & python examples/parallelism/we_are_processes.py && kill $!

"""
from multiprocessing import cpu_count
import os

import tractor
import trio


async def target():
    print(f"Yo, i'm '{tractor.current_actor().name}' "
          f"running in pid {os.getpid()}")
    await trio.sleep_forever()


async def main():

    async with tractor.open_nursery() as n:

        for i in range(cpu_count()):
            await n.run_in_actor(target, name=f'worker_{i}')

        print('This process tree will self-destruct in 1 sec...')
        await trio.sleep(1)

        # you could have done this yourself
        raise Exception('Self Destructed')


if __name__ == '__main__':
    try:
        trio.run(main)
    except Exception:
        print('Zombies Contained')

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 the trio gitter channel!