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Zameer Manji commented on AURORA-1801:
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I am a big fan of making the process fail if the `TaskObserver` thread fails.
That matches up with patterns elsewhere in the code.
We can also prevent the race condition too.
> TaskObserver thread stops refreshing after filesystem race condition
> --------------------------------------------------------------------
>
> Key: AURORA-1801
> URL: https://issues.apache.org/jira/browse/AURORA-1801
> Project: Aurora
> Issue Type: Bug
> Components: Observer
> Reporter: Stephan Erb
>
> It seems like that a race condition accessing the Mesos filesystem layout can bubble
up and terminate the {{TaskObserver}} thread responsible for refreshing the internal data
structure of available tasks. Restarting the observer fixes the problem.
> Exception triggering the issue:
> {code}
> Traceback (most recent call last):
> File "/.pex/install/twitter.common.exceptions-0.3.7-py2-none-any.whl.bce9e54ac7cded79a75603fb4e6bcef2c7d1e6bc/twitter.common.exceptions-0.3.7-py2-none-any.whl/twitter/common/exceptions/__init__.py",
line 126, in _excepting_run
> self.__real_run(*args, **kw)
> File "apache/thermos/observer/task_observer.py", line 135, in run
> File "apache/thermos/observer/detector.py", line 74, in refresh
> File "apache/thermos/observer/detector.py", line 58, in _refresh_detectors
> File "apache/aurora/executor/common/path_detector.py", line 34, in get_paths
> File "apache/aurora/executor/common/path_detector.py", line 34, in <genexpr>
> File "apache/aurora/executor/common/path_detector.py", line 33, in iterate
> File "/usr/lib/python2.7/posixpath.py", line 376, in realpath
> resolved = _resolve_link(component)
> File "/usr/lib/python2.7/posixpath.py", line 399, in _resolve_link
> resolved = os.readlink(path)
> OSError: [Errno 2] No such file or directory: '/var/lib/mesos/slaves/0768bcb3-205d-4409-a726-3001ad3ef902-S10/frameworks/20151001-085346-58917130-5050-37976-0000/executors/thermos-role-env-myname-0-f9fe0318-d39f-49d3-bdf8-e954d5879b33/runs/latest'
> {code}
> Solution space:
> * terminate the observer process if the {{TaskOberver}} thread fails
> * prevent unknown exceptions from aborting the {{TaskOberver}} run loop
> * prevent the observed race condition in {{detector.py}} or {{path_detector.py}}
>
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