AIO Task Bound Context
Context manager that provides a means for context to be set, and retrieved in Python AsyncIO.
Okay so for a concrete example, thing of how Flask handles the current request:
from flask import request
This import, called from anywhere, will import the current request being handled. This is made possible in a way similar to this:
request = None def get_request(): return request def set_request(value): global request request = value
When the HTTP server gets a request, it will call
set_request, then anywhere
in the code another function can call
get_request to get the value.
Here's the kicker: This is not possible with AIO, because multiple tasks may
be running at once, so there are multiple values for
request, rather than
just a single value. Imagine the same piece of code being used in AIO:
import asyncio as aio async def handle_request(request): set_request(request) # generate the response await aio.sleep(1) assert get_request() == request # will fail set_request(None) aio.get_event_loop().run_until_complete(aio.gather( handle_request('value 1'), handle_request('value 2'), ))
Obviously, this is going to be problematic.
aio_task_bound_context attaches a stack of the current context values to the
Task, as well as tracking the parent tasks so that their context
can be inherrited:
import asyncio as aio from aio_task_bound_context import TaskBoundContext class RequestContext(TaskBoundContext): def __init__(self, request): self.request = request def get_value(self): return self.request async def handle_request(request): with RequestContext(request): # generate the response await aio.sleep(1) assert RequestContext.current() == request # will succeed aio.get_event_loop().run_until_complete(aio.gather( handle_request('value 1'), handle_request('value 2'), ))
Python 3.5+ is supported. To run tests across all environments, we use
pyenv, and some quick
virtualenv invocations (yes, we could also use
To run the tests, just run
./tests_runall.sh which will install relevant
Python versions if not already installed, create virtualenvs for them, and
To run tests manually, simply
Copyright 2018 Ricky Cook
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