wsgiref.simple_server.SimpleServer claims to be multithreaded

[sgala]

BPO	8138
Nosy	@pjeby, @djc, @berkerpeksag
PRs	bpo-8138: Initialize wsgiref's SimpleServer as single-threaded #12977
Files	multithread.patch: Patch so that simple_server.py doesn't claim falsely it is multithreaded

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2019-05-24.17:25:12.677>
created_at = <Date 2010-03-14.18:08:54.920>
labels = ['3.8', 'type-bug', 'library']
title = 'wsgiref.simple_server.SimpleServer claims to be multithreaded'
updated_at = <Date 2019-05-24.17:25:12.676>
user = 'https://bugs.python.org/sgala'

bugs.python.org fields:

activity = <Date 2019-05-24.17:25:12.676>
actor = 'berker.peksag'
assignee = 'none'
closed = True
closed_date = <Date 2019-05-24.17:25:12.677>
closer = 'berker.peksag'
components = ['Library (Lib)']
creation = <Date 2010-03-14.18:08:54.920>
creator = 'sgala'
dependencies = []
files = ['36787']
hgrepos = []
issue_num = 8138
keywords = ['patch']
message_count = 6.0
messages = ['101058', '228121', '228262', '228539', '340952', '343413']
nosy_count = 4.0
nosy_names = ['pje', 'sgala', 'djc', 'berker.peksag']
pr_nums = ['12977']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue8138'
versions = ['Python 3.8']

[sgala]

In python 2.6, a server created with wsgiref.simple_server.make_server will
claim to be multithreaded and multiprocess through it wsgi environ. See wsgi.multithread in the browser page after launching

  $ python /usr/lib/python2.6/wsgiref/simple_server.py

The bug is due to the default value in the constructor wsgiref.handlers.SimpleHandler, and it is misleading, as the servier is singlethreaded. It gives problems for any app that wants to change behavior or error on singlethreaded.

The problem can be fixed very simply by patching a "multithreaded=False" argument into the ServerHandler constructor in simple_server.

[BreamoreBoy]

@santiago can you provide a patch for this issue?

[sgala]

Something like this should do it:

$ diff -u /usr/lib/python2.7/wsgiref/simple_server.py{~,}
--- /usr/lib/python2.7/wsgiref/simple_server.py~	2014-10-02 23:32:47.718382895 +0200
+++ /usr/lib/python2.7/wsgiref/simple_server.py	2014-10-02 14:36:10.662220865 +0200
@@ -118,7 +118,8 @@
             return
 
         handler = ServerHandler(
-            self.rfile, self.wfile, self.get_stderr(), self.get_environ()
+            self.rfile, self.wfile, self.get_stderr(), self.get_environ(),
+            multithread = False
         )
         handler.request_handler = self      # backpointer for logging
         handler.run(self.server.get_app())

[berkerpeksag]

Looks like Werkzeug had a workaround for this bug:

https://github.com/mitsuhiko/werkzeug/commit/f9e2fad30d34a6b0737539434c03c07c2bc658d4

[berkerpeksag]

It's not easy to write a test for this, so I might merge PR 12977 without a test.

[berkerpeksag]

New changeset 14738ff by Berker Peksag in branch 'master':
bpo-8138: Initialize wsgiref's SimpleServer as single-threaded (GH-12977)
14738ff