From: Ben Darnell <ben@bendarnell.com>
Date: Sat, 22 Jun 2019 18:39:38 +0000 (-0400)
Subject: docs: Add notice about WindowsSelectorEventLoop on py38
X-Git-Tag: v6.0.3^2~2
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=1bf58c74e77c9f91a9f10bc8eea0fcdffbedd914;p=thirdparty%2Ftornado.git

docs: Add notice about WindowsSelectorEventLoop on py38

Fixes #2608
---

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
 -------------