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Intermittent iOS buildbot failure in test_sock_client_racing #148793

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Intermittent iOS buildbot failure in test_sock_client_racing#148793
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OS-iostestsTests in the Lib/test dirtopic-asynciotype-bugAn unexpected behavior, bug, or error

Description

@mhsmith
mhsmith
opened on Apr 20, 2026

Bug report

Bug description:

This is failing on about 10% of attempts. Usually it passes on a rerun:

But sometimes it fails on the rerun:

 ERROR: test_sock_client_racing (test.test_asyncio.test_sock_lowlevel.KqueueEventLoopTests.test_sock_client_racing)
 ----------------------------------------------------------------------
 Traceback (most recent call last):
   File "/Users/buildbot/Library/Developer/CoreSimulator/Devices/4F9AFDE7-A49A-46AD-B161-FCA22E48EA55/data/Containers/Bundle/Application/3DAA3568-C09B-454E-9E2B-4749EEB89567/iOSTestbed.app/python/lib/python3.15/test/test_asyncio/test_sock_lowlevel.py", line 273, in test_sock_client_racing
     self.loop.run_until_complete(asyncio.wait_for(
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^
         self._basetest_sock_send_racing(listener, sock), 10))
         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   File "/Users/buildbot/Library/Developer/CoreSimulator/Devices/4F9AFDE7-A49A-46AD-B161-FCA22E48EA55/data/Containers/Bundle/Application/3DAA3568-C09B-454E-9E2B-4749EEB89567/iOSTestbed.app/python/lib/python3.15/asyncio/base_events.py", line 724, in run_until_complete
     return future.result()
            ~~~~~~~~~~~~~^^
   File "/Users/buildbot/Library/Developer/CoreSimulator/Devices/4F9AFDE7-A49A-46AD-B161-FCA22E48EA55/data/Containers/Bundle/Application/3DAA3568-C09B-454E-9E2B-4749EEB89567/iOSTestbed.app/python/lib/python3.15/asyncio/tasks.py", line 488, in wait_for
     return await fut
            ^^^^^^^^^
   File "/Users/buildbot/Library/Developer/CoreSimulator/Devices/4F9AFDE7-A49A-46AD-B161-FCA22E48EA55/data/Containers/Bundle/Application/3DAA3568-C09B-454E-9E2B-4749EEB89567/iOSTestbed.app/python/lib/python3.15/test/test_asyncio/test_sock_lowlevel.py", line 196, in _basetest_sock_send_racing
     sock.send(b' ' * size)
     ~~~~~~~~~^^^^^^^^^^^^^
 ConnectionResetError: [Errno 54] Connection reset by peer

@freakboy3742: FYI

CPython versions tested on:

CPython main branch

Operating systems tested on:

Other

Activity

  1. mhsmith
    added
    type-bugAn unexpected behavior, bug, or error
    testsTests in the Lib/test dir
    OS-ios
    on Apr 20, 2026
  2. StanFromIreland
    added
    topic-asyncio
    on Apr 20, 2026

  3. freakboy3742 commented on Apr 20, 2026

    @freakboy3742
    freakboy3742
    on Apr 20, 2026
    Contributor

    Thanks - I had seen that; I wasn't overly concerned because (a) the failure-on-repeat rate is very low, and (b) from what I can make out, the test that is failing is a explicitly testing performance under extreme network load. Obviously it would be preferable to pass the test consistently, but it's also going to be difficult to reproduce (and I haven't had any luck to date reproducing it locally)

    FWIW - there are at least two failure modes that I've seen. They both occur on the sock_send_racing portion of the test. The sock_recv and sock_recv_into portions of the test seem to be stable. It does make me wonder if the problem is some sort of time-based reset after the first sequence of the test.

    1. Timeout on the second socket test:
     Traceback (most recent call last):
   File "/Users/buildbot/Library/Developer/CoreSimulator/Devices/4F9AFDE7-A49A-46AD-B161-FCA22E48EA55/data/Containers/Bundle/Application/5F33C29B-26A9-433F-8EF2-24292B3B9DD8/iOSTestbed.app/python/lib/python3.15/asyncio/tasks.py", line 488, in wait_for
     return await fut
            ^^^^^^^^^
   File "/Users/buildbot/Library/Developer/CoreSimulator/Devices/4F9AFDE7-A49A-46AD-B161-FCA22E48EA55/data/Containers/Bundle/Application/5F33C29B-26A9-433F-8EF2-24292B3B9DD8/iOSTestbed.app/python/lib/python3.15/test/test_asyncio/test_sock_lowlevel.py", line 216, in _basetest_sock_send_racing
     await self.loop.sock_sendall(sock, b'world')
   File "/Users/buildbot/Library/Developer/CoreSimulator/Devices/4F9AFDE7-A49A-46AD-B161-FCA22E48EA55/data/Containers/Bundle/Application/5F33C29B-26A9-433F-8EF2-24292B3B9DD8/iOSTestbed.app/python/lib/python3.15/asyncio/selector_events.py", line 562, in sock_sendall
     return await fut
            ^^^^^^^^^
 asyncio.exceptions.CancelledError
 
 The above exception was the direct cause of the following exception:
 
 Traceback (most recent call last):
   File "/Users/buildbot/Library/Developer/CoreSimulator/Devices/4F9AFDE7-A49A-46AD-B161-FCA22E48EA55/data/Containers/Bundle/Application/5F33C29B-26A9-433F-8EF2-24292B3B9DD8/iOSTestbed.app/python/lib/python3.15/test/test_asyncio/test_sock_lowlevel.py", line 273, in test_sock_client_racing
     self.loop.run_until_complete(asyncio.wait_for(
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^
         self._basetest_sock_send_racing(listener, sock), 10))
         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   File "/Users/buildbot/Library/Developer/CoreSimulator/Devices/4F9AFDE7-A49A-46AD-B161-FCA22E48EA55/data/Containers/Bundle/Application/5F33C29B-26A9-433F-8EF2-24292B3B9DD8/iOSTestbed.app/python/lib/python3.15/asyncio/base_events.py", line 724, in run_until_complete
     return future.result()
            ~~~~~~~~~~~~~^^
   File "/Users/buildbot/Library/Developer/CoreSimulator/Devices/4F9AFDE7-A49A-46AD-B161-FCA22E48EA55/data/Containers/Bundle/Application/5F33C29B-26A9-433F-8EF2-24292B3B9DD8/iOSTestbed.app/python/lib/python3.15/asyncio/tasks.py", line 487, in wait_for
     async with timeouts.timeout(timeout):
                ~~~~~~~~~~~~~~~~^^^^^^^^^
   File "/Users/buildbot/Library/Developer/CoreSimulator/Devices/4F9AFDE7-A49A-46AD-B161-FCA22E48EA55/data/Containers/Bundle/Application/5F33C29B-26A9-433F-8EF2-24292B3B9DD8/iOSTestbed.app/python/lib/python3.15/asyncio/timeouts.py", line 114, in __aexit__
     raise TimeoutError from exc_val
 TimeoutError
    1. A connection reset error
     Traceback (most recent call last):
   File "/Users/buildbot/Library/Developer/CoreSimulator/Devices/4F9AFDE7-A49A-46AD-B161-FCA22E48EA55/data/Containers/Bundle/Application/3DAA3568-C09B-454E-9E2B-4749EEB89567/iOSTestbed.app/python/lib/python3.15/test/test_asyncio/test_sock_lowlevel.py", line 273, in test_sock_client_racing
     self.loop.run_until_complete(asyncio.wait_for(
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^
         self._basetest_sock_send_racing(listener, sock), 10))
         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   File "/Users/buildbot/Library/Developer/CoreSimulator/Devices/4F9AFDE7-A49A-46AD-B161-FCA22E48EA55/data/Containers/Bundle/Application/3DAA3568-C09B-454E-9E2B-4749EEB89567/iOSTestbed.app/python/lib/python3.15/asyncio/base_events.py", line 724, in run_until_complete
     return future.result()
            ~~~~~~~~~~~~~^^
   File "/Users/buildbot/Library/Developer/CoreSimulator/Devices/4F9AFDE7-A49A-46AD-B161-FCA22E48EA55/data/Containers/Bundle/Application/3DAA3568-C09B-454E-9E2B-4749EEB89567/iOSTestbed.app/python/lib/python3.15/asyncio/tasks.py", line 488, in wait_for
     return await fut
            ^^^^^^^^^
   File "/Users/buildbot/Library/Developer/CoreSimulator/Devices/4F9AFDE7-A49A-46AD-B161-FCA22E48EA55/data/Containers/Bundle/Application/3DAA3568-C09B-454E-9E2B-4749EEB89567/iOSTestbed.app/python/lib/python3.15/test/test_asyncio/test_sock_lowlevel.py", line 196, in _basetest_sock_send_racing
     sock.send(b' ' * size)
     ~~~~~~~~~^^^^^^^^^^^^^
 ConnectionResetError: [Errno 54] Connection reset by peer

  4. mhsmith commented on Apr 21, 2026

    @mhsmith
    mhsmith
    on Apr 21, 2026
    MemberAuthor

    Also, the GitHub buildbot comments aren't including anything useful. This might be because every line in the test log has an extra space at the start.

  5. serhiy-storchaka
    added this to asyncioon Jul 3, 2026
  6. github-project-automation
    moved this to Todo in asyncioon Jul 3, 2026

  7. kumaraditya303 commented on Jul 19, 2026

    @kumaraditya303
    kumaraditya303
    on Jul 19, 2026
    Contributor

    What's the status of this?

  8. freakboy3742 commented on Jul 19, 2026

    @freakboy3742
    freakboy3742
    on Jul 19, 2026
    Contributor

    It's still happening - but it's a lot less frequent than it was. Looking at the last 200 builds on Buildbot, there are:

    • 7 failures that passed on the re-run (all test_sock_client_racing failures).
    • 1 failure that failed a second time on re-run (this build, on Jun 28).
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    OS-iostestsTests in the Lib/test dirtopic-asynciotype-bugAn unexpected behavior, bug, or error

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