From 1bf58c74e77c9f91a9f10bc8eea0fcdffbedd914 Mon Sep 17 00:00:00 2001 From: Ben Darnell Date: Sat, 22 Jun 2019 14:39:38 -0400 Subject: [PATCH] docs: Add notice about WindowsSelectorEventLoop on py38 Fixes #2608 --- docs/index.rst | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/docs/index.rst b/docs/index.rst index ac5ac6196..0239606ff 100644 --- a/docs/index.rst +++ b/docs/index.rst @@ -120,6 +120,13 @@ development use. Without reworking Tornado IOLoop interface, it's not possible to add a native Tornado Windows IOLoop implementation or leverage Windows' IOCP support from frameworks like AsyncIO or Twisted. +On Windows, Tornado requires the ``WindowsSelectorEventLoop``. This is +the default in Python 3.7 and older, but Python 3.8 defaults to an +event loop that is not compatible with Tornado. Applications that use +Tornado on Windows with Python 3.8 must call +``asyncio.set_event_loop_policy(asyncio.WindowsSelectorEventLoopPolicy())`` +at the beginning of their ``main`` file/function. + Documentation ------------- -- 2.47.2