python
gh-123720: When closing an asyncio server, stop the handlers
Since 3.12, when server.wait_closed() was fixed, cancelling a serve_forever() call would wait for the last handler to exit, which may be never if it is waiting to read from a connection that is never closed by the client. To fix this, we insert a close_clients() call in the exit sequence (between close() and wait_closed()).
The repro shows that in 3.11 you need only a single ^C to stop the server; in 3.12 you need two. The fix indeed undoes that regression.
Some philosophical question remain:
- Should we call close_clients() in close(), so everyone who closes a server gets the same benefit?
- Should we use abort_clients() instead? (I think it's better to allow handlers to catch the cancellation and e.g. send a "goodbye" message to the client.)
- Is this a bugfix (backportable) or a new feature? I'm inclined to call it a bugfix, given the regressions in 3.12 and beyond.
Note that there's still a difference with 3.11: in 3.11, the handler receives a CancelledError; in main with this PR added, the handler receives an empty string, indicating that the connection was closed (by close_clients()). Maybe I should do something that actually cancels the handlers? I will look into the feasibility of this.
- Issue: gh-123720
