Server handler halts after client connection closed

[ykvch]

Pre:

Linux with curl installed.
Python 3.6.3 with aiohttp installed

Server script (server.py):

# coding: utf-8

from asyncio import sleep
from aiohttp import web


async def handle_stream(request):
    data = 'Їїїїї'
    resp = web.StreamResponse()
    resp.content_length = len(data)
    await resp.prepare(request)

    resp.write(data.encode("utf-8"))
    await sleep(1)  # if sleep present, handle ends here, next line not executed
    raise RuntimeError("this should happen")


app = web.Application()
app.router.add_get("/", handle_stream)
web.run_app(app)

Steps:

1. Run server script: python server.py
2. On the same host run (bash): curl -vv http://127.0.0.1:8080/
3. Observe server.py script console output.

Expected:

3. RuntimeError("this should happen") message 1 second after client disconnects.

Actual:

3. Server runs without messages (raise... line never executed)

Note: If await sleep... line (above the raise...) removed then exception does get triggered.

[fafhrd91]

This is expected behavior, await sleep raises CancelledError

[ykvch]

Thanks.
Now it clearly looks like a duplicate/similar to #1430

Solution:
Explicitly use shield around anything that has to be executed independently of connection cancellation.

[lock]

This thread has been automatically locked since there has not been any recent activity after it was closed. Please open a [new issue] for related bugs.
If you feel like there's important points made in this discussion, please include those exceprts into that [new issue].
[new issue]: https://github.com/aio-libs/aiohttp/issues/new