New submission from Tom <t...@collider.in>:
Consider this program:
import asyncio
async def handler(r, w):
raise RuntimeError
async def main():
server = await asyncio.start_server(handler, host='localhost',
port=1234)
r, w = await asyncio.open_connection(host='localhost', port=1234)
await server.serve_forever()
server.close()
asyncio.run(main())
The RuntimeError is not retrievable via the serve_forever coroutine. To my
knowledge, there is no feature of the asyncio API which causes the server to
stop on an exception and retrieve it. I have also tried wrapping serve_forever
in a Task, and waiting on the coro with FIRST_EXCEPTION.
This severely complicates testing asyncio servers, since failing tests hang
forever if the failure occurs in a callback.
It should be possible to configure the server to end if a callback fails, e.g.
by a 'stop_on_error' kwarg to start_server (defaulting to False for
compatibility).
I know this isn't a technical problem, since AnyIO, which uses asyncio, does
this by default. This equivalent program ends after the exception:
import anyio
async def handler(client):
raise RuntimeError
async def main():
async with anyio.create_task_group() as tg:
listener = await anyio.create_tcp_listener(local_host='localhost',
local_port=1234)
await tg.spawn(listener.serve, handler)
async with await anyio.connect_tcp('localhost', 1234) as client:
pass
anyio.run(main)
----------
components: asyncio
messages: 382265
nosy: asvetlov, tmewett, yselivanov
priority: normal
severity: normal
status: open
title: Exceptions in asyncio.Server callbacks are not retrievable
versions: Python 3.7
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Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue42526>
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