process cleanup for ReactorBuilder-based tests loops indefinitely if processes do not exit

[zooko]

 http://buildbot.twistedmatrix.com/builders/cygwin-py2.5-select/builds/1

Produces many hundreds or thousands of this line in the test.log:

2008-08-26 15:29:02-0700 [-] ReactorBuilder.tearDown reaping some processes {2540: <PTYProcess pid=2540 status=-1>}

Followed by many of this:

2008-08-26 15:29:10-0700 [-] ReactorBuilder.tearDown reaping some processes {2524: <PTYProcess pid=2524 status=-1>}

and eventually I stopped it.

[exarkun]

It seems the process started by twisted.internet.test.test_process.ProcessTestsBuilder_PollReactor.test_childConnectionLost never exits. It is supposed to exit when it receives a blank line on stdin, which the test sends it after sending two other lines.

It seems like the test method actually ran to completion and all the events it expected did happen because the infinite log message happens in tearDown which should only run after the test method has returned.

So the question here may be about why the child process isn't exiting when it is expected to.

[zooko]

Maybe it is waiting for a DOS-style blank line: '\r\n' ?

[exarkun]

Maybe. I don't have cygwin installed anywhere, so I can't test this.

[zooko]

duplicate of #3529

[exarkun]

Even if cygwin is broken, the tests shouldn't get stuck in a loop. #3529 can be for fixing cygwin support somehow. I'm using this ticket to fix the getting stuck behavior.

[exarkun]

(In [25347]) Branching to 'process-cleanup-loop-3398'

[exarkun]

Can you try the branch on cygwin?

I expect the tests will fail, but the suite should run to completion at least.

[itamar]

This is happening on non-cygwin platforms as well, e.g.:  http://buildbot.twistedmatrix.com/builders/fedora32-py2.5-reactors/builds/1553/steps/poll/logs/test.log

[itamarst]

(In [34151]) Branching to 'process-cleanup-loop-3398-2'

[itamarst]

(In [34153]) Merge process-cleanup-loop-3398-2: Cleanup after zombie test processes.

Author: exarkun Review: itamar Fixes: #3398

Hopefully this will make the Fedora buildbot stop getting into infinite loops.