Public bug reported:
MAAS uses twisted and we have ran into an issue where it seems to be
that the MAAS's networking monitoring services has a lock file to ensure
that only one processes updates the networking information. If the
processes gets killed, the lock file stays, pointing to the PID the
killed regiond process had.
Now what normally happens is that another process tries to acquire the
lock, sees that the lock points to a killed PID , and recreates the
lock.
This normally works, but what can happen is that the killed PID gets
recycled, so that the lock now points to a PID which the maas user isn't
allowed to kill. Now a PermissionError is raised, that the lock file
implementation doesn't handle this case, and the networking monitoring
service can never start.
Here is the traceback:
2019-10-31 08:12:13 twisted.scripts: [info] twistd 17.9.0 (/usr/bin/python3
3.6.8) starting up.
2019-10-31 08:12:13 twisted.scripts: [info] reactor class:
twisted.internet.asyncioreactor.AsyncioSelectorReactor.
2019-10-31 08:12:14 -: [critical] Unhandled Error
Traceback (most recent call last):
File "/usr/lib/python3/dist-packages/twisted/internet/task.py", line
194, in start
self()
File "/usr/lib/python3/dist-packages/twisted/internet/task.py", line
239, in __call__
d = defer.maybeDeferred(self.f, *self.a, **self.kw)
File "/usr/lib/python3/dist-packages/twisted/internet/defer.py", line
150, in maybeDeferred
result = f(*args, **kw)
File "/usr/lib/python3/dist-packages/twisted/internet/defer.py", line
1532, in unwindGenerator
return _inlineCallbacks(None, gen, Deferred())
--- <exception caught here> ---
File "/usr/lib/python3/dist-packages/twisted/internet/defer.py", line
1386, in _inlineCallbacks
result = g.send(result)
File
"/usr/lib/python3/dist-packages/provisioningserver/utils/services.py", line
1001, in updateInterfaces
responsible = self._assumeSoleResponsibility()
File
"/usr/lib/python3/dist-packages/provisioningserver/utils/services.py", line
1077, in _assumeSoleResponsibility
self._lock.acquire()
File "/usr/lib/python3/dist-packages/provisioningserver/utils/fs.py",
line 467, in acquire
if not self._fslock.lock():
File "/usr/lib/python3/dist-packages/twisted/python/lockfile.py",
line 185, in lock
kill(int(pid), 0)
builtins.PermissionError: [Errno 1] Operation not permitted
** Affects: twisted (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/1851737
Title:
PermissionError for lock file
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