homepage

The process was killed (SIGKILL).
See also bpo-30356.
http://buildbot.python.org/all/builders/x86-64%20Sierra%203.x/builds/765/steps/test/logs/stdio
======================================================================
FAIL: test_many_processes (test.test_multiprocessing_spawn.WithProcessesTestProcess)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/Users/buildbot/buildarea/3.x.billenstein-sierra/build/Lib/test/_test_multiprocessing.py", line 505, in test_many_processes
 self.assertEqual(p.exitcode, -signal.SIGTERM)
AssertionError: -9 != -15

I failed to reproduce the bug on Linux.

test_many_processes() test was added by Antoine Pitrou in bpo-30589. This test was mentionned in bpo-30703.

test_many_processes() is made in two steps. The bug occurs at the second step which calls proc.terminate() on processes. Code of the test:
 @classmethod
 def _sleep_some(cls):
 time.sleep(100)
 @classmethod
 def _test_sleep(cls, delay):
 time.sleep(delay)
 def test_many_processes(self):
 if self.TYPE == 'threads':
 self.skipTest('test not appropriate for {}'.format(self.TYPE))
 sm = multiprocessing.get_start_method()
 N = 5 if sm == 'spawn' else 100
 # Try to overwhelm the forkserver loop with events
 procs = [self.Process(target=self._test_sleep, args=(0.01,))
 for i in range(N)]
 for p in procs:
 p.start()
 for p in procs:
 join_process(p)
 for p in procs:
 self.assertEqual(p.exitcode, 0)
 procs = [self.Process(target=self._sleep_some)
 for i in range(N)]
 for p in procs:
 p.start()
 time.sleep(0.001) # let the children start...
 for p in procs:
 p.terminate()
 for p in procs:
 join_process(p)
 if os.name != 'nt':
 for p in procs:
 self.assertEqual(p.exitcode, -signal.SIGTERM) # <--- HERE
I'm not sure about the "time.sleep(0.001) # let the children start...". It looks like a weak synchronization. Maybe if the system is heavily loaded, the signal is sent before Python registered signal handlers? 1 ms seems short to start Python. On my Linux laptop, it's closer to 15 ms.

> It looks like a weak synchronization.
It is. I don't remember exactly why I had to add this, I can't reproduce any issue without it anymore...
> the signal is sent before Python registered signal handlers?
Python signal handlers are not relevant here, we're sending SIGTERM which kills the process.

It seems other people have similar issues:
https://github.com/libuv/libuv/issues/1226
Perhaps we need to relax the test on OSX :-/

Antoine: "It seems other people have similar issues: https://github.com/libuv/libuv/issues/1226 Perhaps we need to relax the test on OSX :-/"
Oh thanks for the confirmation. I proposed a patch to accept -SIGKILL on macOS: PR 3857.

New changeset e6cfdefa0c2f5bda177e49b228c2c7528f7c239c by Victor Stinner in branch 'master':
bpo-31510: Fix multiprocessing test_many_processes() on macOS (#3857)
https://github.com/python/cpython/commit/e6cfdefa0c2f5bda177e49b228c2c7528f7c239c