STINNER Victor <vstin...@redhat.com> added the comment:
Ben: > Concretely, this is a concern for Tornado (which requires add_reader()) and > applications in the scientific python community (including Jupyter) which > depend on it. If you need add_reader/add_writer in Python 3.8, you can switch the default event loop to selector at the beginning of your application: if sys.platform == 'win32': asyncio.set_event_loop_policy(asyncio.WindowsSelectorEventLoopPolicy()) Yury: > If there's no native API for that, I guess we can spawn a thread with a > 'select()' call to emulate this API? There is no native API because IOCP design is to run an asynchronous read/write and then wait for its completion. Unix select() has the opposite design: check if a file descriptor is read for read/write. Reimplementing add_reader/add_writer using a single select() call in a thread sounds like a good idea, but we have to make sure that it can be stopped whenever using a dedicated "self-pipe" (to awake the blocked select(), so loop.close() can stop this thread. See attached proof-of-concept: selector_thread.py: run a selector in a separated thread which pass pack events to the loop using call_soon(). I would prefer to use a single selector to better scale with the number of FD. Note: On Windows, select() only supports sockets. Note: select.select() may be extended to support more than 512 sockets on Windows, see bpo-28708 :-) Yury: > Another question: if we fix this, would you allow this to go in beta2/3? > Strictly speaking it's going to be a new functionality. It's a new feature, so it can wait for Python 3.9 :-) I don't see any regression here, as soon as you can opt-in for SelectorEventLoop. ---------- Added file: https://bugs.python.org/file48434/selector_thread.py _______________________________________ Python tracker <rep...@bugs.python.org> <https://bugs.python.org/issue37373> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
