Test test_multi_timer fails on 1-core-VM

[bmwiedemann]

What did you try to do?

build openSUSE python-pycurl package
on 1-core-VM or with
taskset 1 osc build -j1

What happened?

osc checkout openSUSE:Factory/python-pycurl && cd $_
taskset 1 osc build -j1

output:

======================================================================
FAIL: test_multi_timer (tests.multi_timer_test.MultiSocketTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/abuild/rpmbuild/BUILD/pycurl-7.43.0.2/tests/multi_timer_test.py", line 83, in test_multi_timer
    assert timers[0] >= 0
AssertionError

===Flaky Test Report===

What did you expect to happen?

tests should pass

What is the PycURL version?

(output of pycurl.version)
pycurl-7.43.0.2
libcurl4-7.61.1

What is your Python version?

(output of python -V)
python3-3.6.5-3.4 and/or python-2.7.15-1.2

What is your operating system and its version?

openSUSE Tumbleweed 2018-09-xx

Is this the most recent PycURL release?

yes

Did you check libcurl behavior?

no

[bmwiedemann]

Once I also got

======================================================================
FAIL: test_opensocketfunction_collection (tests.multi_memory_mgmt_test.MultiMemoryMgmtTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/abuild/rpmbuild/BUILD/pycurl-7.43.0.2/tests/multi_memory_mgmt_test.py", line 18, in test_opensocketfunction_collection
    self.check_callback(pycurl.M_SOCKETFUNCTION)
  File "/home/abuild/rpmbuild/BUILD/pycurl-7.43.0.2/tests/multi_memory_mgmt_test.py", line 42, in check_callback
    self.assertTrue(new_object_count in (object_count, object_count-1))
AssertionError: False is not true 

===Flaky Test Report===

but not sure how reproducible this one is.

[p]

Is this test failing each time you run it on that OS?

[bmwiedemann]

Yes, it consistently fails on openSUSE Tumbleweed/Factory (libcurl 7.61.1)
unless I allow it to use 2 or more CPU cores.

It seems to (mostly) work on older openSUSE Leap 15.0 with libcurl 7.60.0 . Some random 'getting stuck' issues there.

This is just exchanging the user-space (with chroot), not the kernel.

[p]

Okay thank you, that test predates me and it is not immediately obvious to me how important that check is. I take it the timer event is firing immediately, but only on a 1 core vm? I will queue up looking into the test to understand it better.

[bmwiedemann]

ping. did you find time to look into it?

[p]

Haven't gotten to it yet, in fact there is a number of things in the queue prior to this issue. What is its impact for you?

[bmwiedemann]

It is low impact atm. I'm verifying reproducible builds for openSUSE and vary several parameters, including number of CPUs, because it sometimes matters for build results (e.g. via races).
It just creates some extra noise there when reviewing results.

[bmwiedemann]

actually, it became even less of an issue, because the tests were split off the main package build. Reproducer is now

taskset 1 osc build -j1 --noservice -M test

[p]

I am going to close this since I don't see myself working on it in the foreseeable future.

Patches to fix are welcome.