[jira] [Created] (AURORA-1801) TaskObserver thread stops refreshing after filesystem race condition

["Stephan Erb (JIRA)" <ji...@apache.org>]

Stephan Erb created AURORA-1801:
-----------------------------------

             Summary: 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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