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socketserver.ForkingMixIn.server_close() leaks zombie processes #75334

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socketserver.ForkingMixIn.server_close() leaks zombie processes#75334

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3.7 (EOL)end of lifeend of lifeperformancePerformance or resource usagePerformance or resource usagetestsTests in the Lib/test dirTests in the Lib/test dir

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vstinner

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on Aug 9, 2017

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BPO	31151
Nosy	@vstinner, @ned-deily
PRs	bpo-31151: Add socketserver.ForkingMixIn.server_close() #3057 bpo-31233, bpo-31151: Document socketserver changes #5417
Files	forkingmixin_sleep.patch

^{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 2018-05-29.22:01:13.402>
created_at = <Date 2017-08-09.00:40:39.921>
labels = ['3.7', 'tests', 'performance']
title = 'socketserver.ForkingMixIn.server_close() leaks zombie processes'
updated_at = <Date 2018-05-29.22:01:13.401>
user = 'https://github.com/vstinner'

bugs.python.org fields:

activity = <Date 2018-05-29.22:01:13.401>
actor = 'vstinner'
assignee = 'none'
closed = True
closed_date = <Date 2018-05-29.22:01:13.402>
closer = 'vstinner'
components = ['Tests']
creation = <Date 2017-08-09.00:40:39.921>
creator = 'vstinner'
dependencies = []
files = ['47072']
hgrepos = []
issue_num = 31151
keywords = ['patch']
message_count = 13.0
messages = ['299959', '299960', '300074', '300084', '300106', '302013', '302015', '303041', '311015', '311022', '311093', '316834', '318116']
nosy_count = 2.0
nosy_names = ['vstinner', 'ned.deily']
pr_nums = ['3057', '5417']
priority = None
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'resource usage'
url = 'https://bugs.python.org/issue31151'
versions = ['Python 3.6', 'Python 3.7']

Activity

vstinner commented on Aug 9, 2017
vstinner
on Aug 9, 2017
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It seems like test_socketserver leaks child processes on the "x86 Gentoo Refleaks 3.6" buildbot, but I'm unable to reproduce the bug.

http://buildbot.python.org/all/builders/x86%20Gentoo%20Refleaks%203.6/builds/49/steps/test/logs/stdio

0:48:11 load avg: 3.91 [154/405/2] test_socketserver failed -- running: test_decimal (630 sec)
Warning -- reap_children() reaped child process 1044
beginning 6 repetitions
123456
Warning -- reap_children() reaped child process 1104
Warning -- reap_children() reaped child process 1115
.Warning -- reap_children() reaped child process 1170
Warning -- reap_children() reaped child process 1175
Warning -- reap_children() reaped child process 1184
.Warning -- reap_children() reaped child process 1249
.Warning -- reap_children() reaped child process 1311
Warning -- reap_children() reaped child process 1316
...
test_socketserver leaked [1, 1, 1] memory blocks, sum=3

(...)

test_ForkingUnixStreamServer (test.test_socketserver.SocketServerTest) ... creating server
ADDR = /tmp/unix_socket.hqh5x95a
CLASS = <class 'test.test_socketserver.ForkingUnixStreamServer'>
server running
test client 0
test client 1
test client 2
waiting for server
done
Warning -- reap_children() reaped child process 17938
ok

test_ForkingUnixDatagramServer (test.test_socketserver.SocketServerTest) ... creating server
ADDR = /tmp/unix_socket.gry6ulhp
CLASS = <class 'test.test_socketserver.ForkingUnixDatagramServer'>
server running
test client 0
test client 1
test client 2
waiting for server
done
Warning -- reap_children() reaped child process 18212
ok

test_ForkingUDPServer (test.test_socketserver.SocketServerTest) ... creating server
ADDR = ('127.0.0.1', 43415)
CLASS = <class 'socketserver.ForkingUDPServer'>
server running
test client 0
test client 1
test client 2
waiting for server
done
Warning -- reap_children() reaped child process 18281
ok
test_ForkingUnixDatagramServer (test.test_socketserver.SocketServerTest)
vstinner
added
testsTests in the Lib/test dirTests in the Lib/test dir

performancePerformance or resource usagePerformance or resource usage
on Aug 9, 2017
vstinner commented on Aug 9, 2017
vstinner
on Aug 9, 2017
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Ah, the master branch is also affected. Example:

http://buildbot.python.org/all/builders/x86%20Gentoo%20Refleaks%203.x/builds/47/steps/test/logs/stdio

1:35:05 load avg: 4.64 [212/406] test_socketserver passed -- running: test_subprocess (370 sec)
beginning 6 repetitions
123456
Warning -- reap_children() reaped child process 4641
.Warning -- reap_children() reaped child process 4708
..Warning -- reap_children() reaped child process 4832
.Warning -- reap_children() reaped child process 4916
Warning -- reap_children() reaped child process 4921
..
vstinner
added
3.7 (EOL)end of lifeend of life
on Aug 9, 2017
vstinner
changed the title ~~[-][3.6] test_socketserver: Warning -- reap_children() reaped child process[/-]~~ [+]test_socketserver: Warning -- reap_children() reaped child process[/+] on Aug 9, 2017
vstinner commented on Aug 10, 2017
vstinner
on Aug 10, 2017
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The problem is that socketserver.ForkinMixin doesn't wait until all children completes. It's only calls os.waitpid() in non-blocking module (using os.WNOHANG) after each loop iteration. If a child process completes after the last call to ForkingMixIn.collect_children(), the server leaks zombie processes.

The server must wait until all children completes. Attached PR implements that.

The bug was be reproduced with the attached forkingmixin_sleep.patch.

haypo@selma$ ./python -m test -v -u all test_socketserver --fail-env-changed -m '*Fork*'
(...)
Warning -- reap_children() reaped child process 17093
Warning -- reap_children() reaped child process 17094
(...)
vstinner commented on Aug 10, 2017
vstinner
on Aug 10, 2017
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New changeset aa8ec34 by Victor Stinner in branch 'master':
bpo-31151: Add socketserver.ForkingMixIn.server_close() (bpo-3057)
aa8ec34
vstinner commented on Aug 10, 2017
vstinner
on Aug 10, 2017
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bpo-31010 has been marked as a duplicate of this issue.
vstinner
changed the title ~~[-]test_socketserver: Warning -- reap_children() reaped child process[/-]~~ [+]socketserver.ForkingMixIn.server_close() leaks zombie processes[/+] on Aug 18, 2017
vstinner commented on Sep 13, 2017
vstinner
on Sep 13, 2017
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I created a thread on the python-dev mailing list to discuss this issue:
https://mail.python.org/pipermail/python-dev/2017-August/148826.html
vstinner commented on Sep 13, 2017
vstinner
on Sep 13, 2017
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I tag this issue as release blocker as a remainder that we have to agree how to handle threads/processes before Python 3.7 feature freeze.

See also bpo-31233: socketserver.ThreadingMixIn leaks running threads after server_close().
vstinner
added
release-blocker
on Sep 13, 2017
ned-deily
added
deferred-blocker
and removed
release-blocker
on Sep 18, 2017
vstinner commented on Sep 26, 2017
vstinner
on Sep 26, 2017
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I proposed the bpo-31593 to fix the issue differently in Python 3.6 (and maybe also Python 2.7).
ned-deily commented on Jan 28, 2018
ned-deily
on Jan 28, 2018
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What's the status of this? Feature freeze is here!
vstinner commented on Jan 28, 2018
vstinner
on Jan 28, 2018
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What's the status of this? Feature freeze is here!

This issue is very to https://bugs.python.org/issue31233#msg311021 as it's status:

The commit aa8ec34 is backward incompatible and it's not documented

There is no option to opt-in for the previous behaviour (exit without waiting for child processes)

For beta1, IMHO it's ok to keep the current status. But I would like to see this issue fixed before 3.7 final. Either revert my change, or do something else.
vstinner commented on Jan 29, 2018
vstinner
on Jan 29, 2018
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New changeset db8189b by Victor Stinner in branch 'master':
bpo-31233, bpo-31151: Document socketserver changes (bpo-5417)
db8189b
vstinner commented on May 16, 2018
vstinner
on May 16, 2018
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I created bpo-33540: "socketserver: Add an opt-in option to get Python 3.6 behaviour on server_close()". I set the release blocker priority on this new issue.
vstinner
removed
deferred-blocker
on May 16, 2018
vstinner commented on May 29, 2018
vstinner
on May 29, 2018
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The bug has been fixed in Python 3.7.
vstinner
closed this as completed on May 29, 2018
ezio-melotti
transferred this issue from on Apr 10, 2022

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socketserver.ForkingMixIn.server_close() leaks zombie processes #75334

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Activity

vstinner commented on Aug 9, 2017

vstinner commented on Aug 9, 2017

vstinner commented on Aug 10, 2017

vstinner commented on Aug 10, 2017

vstinner commented on Aug 10, 2017

vstinner commented on Sep 13, 2017

vstinner commented on Sep 13, 2017

vstinner commented on Sep 26, 2017

ned-deily commented on Jan 28, 2018

vstinner commented on Jan 28, 2018

vstinner commented on Jan 29, 2018

vstinner commented on May 16, 2018

vstinner commented on May 29, 2018

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