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socketserver.ForkingMixIn.server_close() leaks zombie processes #75334
Description
| BPO | 31151 |
|---|---|
| Nosy | @vstinner, @ned-deily |
| PRs | |
| Files |
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 commentedon Aug 9, 2017
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 commentedon Aug 9, 2017
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
..
[-][3.6] test_socketserver: Warning -- reap_children() reaped child process[/-][+]test_socketserver: Warning -- reap_children() reaped child process[/+]vstinner commentedon Aug 10, 2017
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 commentedon Aug 10, 2017
New changeset aa8ec34 by Victor Stinner in branch 'master':
bpo-31151: Add socketserver.ForkingMixIn.server_close() (bpo-3057)
aa8ec34
vstinner commentedon Aug 10, 2017
bpo-31010 has been marked as a duplicate of this issue.
[-]test_socketserver: Warning -- reap_children() reaped child process[/-][+]socketserver.ForkingMixIn.server_close() leaks zombie processes[/+]vstinner commentedon Sep 13, 2017
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 commentedon Sep 13, 2017
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 commentedon Sep 26, 2017
I proposed the bpo-31593 to fix the issue differently in Python 3.6 (and maybe also Python 2.7).
ned-deily commentedon Jan 28, 2018
What's the status of this? Feature freeze is here!
vstinner commentedon Jan 28, 2018
This issue is very to https://bugs.python.org/issue31233#msg311021 as it's status:
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 commentedon Jan 29, 2018
New changeset db8189b by Victor Stinner in branch 'master':
bpo-31233, bpo-31151: Document socketserver changes (bpo-5417)
db8189b
vstinner commentedon May 16, 2018
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 commentedon May 29, 2018
The bug has been fixed in Python 3.7.