New submission from Aymeric Augustin <aymeric.augus...@m4x.org>:
**Summary** 1. Is it correct for `Server.wait_closed()` (as implemented in asyncio) to be a no-op after `Server.close()`? 2. How can I tell that all incoming connections have been received by `connection_made()` after `Server.close()`? **Details** After calling `Server.close()`, `_sockets is None`, which makes `Server.wait_closed()` a no-op: it returns immediately without doing anything (as mentioned in https://bugs.python.org/issue33727). I'm not sure why the docs suggest to call `wait_closed()` after `close()` if it's a no-op. My best guess is: "this design supports third-party event loops that requires an asynchronous API for closing servers, but the built-in event loops don't need that". Does someone know? I wrote a very simple server that merely accepts connections. I ran experiments where I saturate the server with incoming client connections and close it. I checked what happens around `close()` (and `wait_closed()` -- but as it doesn't do anything after `close()` I'll just say `close()` from now on.) The current implementation appears to work as documented, assuming an rather low level interpretation of the docs of `Server.close()`. > Stop serving: close listening sockets and set the sockets attribute to None. Correct -- I'm not seeing any `accept` calls in `BaseSelectorEventLoop._accept_connection` after `close()`. > The sockets that represent existing incoming client connections are left open. Correct -- if "existing incoming client connections" is interpreted as "client connections that have gone through `accept`". > The server is closed asynchronously, use the wait_closed() coroutine to wait > until the server is closed. I'm seeing calls to `connection_made()` _after_ `close()` because `BaseSelectorEventLoop._accept_connection2` triggers `connection_made()` asynchronously with `call_soon()`. This is surprising for someone approaching asyncio from the public API rather than the internal implementation. `connection_made()` is the first contact with new connections. The concept of "an existing incoming client connection for which `connection_made()` wasn't called yet" is unexpected. This has practical consequences. Consider a server that keeps track of established connections via `connection_made` and `connection_lost`. If this server calls `Server.close()`, awaits `Server.wait_closed()`, makes a list of established connections and terminates them, there's no guarantee that all connections will be closed. Indeed, new connections may appear and call `connection_made()` after `close()` and `wait_closed()` returned! `wait_closed()` seems ineffective for this use case. ---------- components: asyncio messages: 326725 nosy: asvetlov, aymeric.augustin, yselivanov priority: normal severity: normal status: open title: Counter-intuitive behavior of Server.close() / wait_closed() type: behavior versions: Python 3.7 _______________________________________ Python tracker <rep...@bugs.python.org> <https://bugs.python.org/issue34852> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
