Preflight check for log dirs

[Robert Collins]

We just had an inscrutable error about missing logdirs:
 /home/mthaddon/bzr-sftp-qastaging start
Starting bzr-sftp: twistdTraceback (most recent call last):
  File "/srv/bazaar.qastaging.launchpad.net/qastaging/launchpad/bin/twistd", line 26, in <module>
    twisted.scripts.twistd.run()
  File "/srv/bazaar.qastaging.launchpad.net/qastaging/launchpad-rev-11738/eggs/Twisted-10.1.0-py2.6-linux-x86_64.egg/twisted/scripts/twistd.py", line 27, in run
    app.run(runApp, ServerOptions)
  File "/srv/bazaar.qastaging.launchpad.net/qastaging/launchpad-rev-11738/eggs/Twisted-10.1.0-py2.6-linux-x86_64.egg/twisted/application/app.py", line 626, in run
    runApp(config)
  File "/srv/bazaar.qastaging.launchpad.net/qastaging/launchpad-rev-11738/eggs/Twisted-10.1.0-py2.6-linux-x86_64.egg/twisted/scripts/twistd.py", line 23, in runApp
    _SomeApplicationRunner(config).run()
  File "/srv/bazaar.qastaging.launchpad.net/qastaging/launchpad-rev-11738/eggs/Twisted-10.1.0-py2.6-linux-x86_64.egg/twisted/application/app.py", line 376, in run
    self.logger.start(self.application)
  File "/srv/bazaar.qastaging.launchpad.net/qastaging/launchpad-rev-11738/eggs/Twisted-10.1.0-py2.6-linux-x86_64.egg/twisted/application/app.py", line 216, in start
    observer = self._getLogObserver()
  File "/srv/bazaar.qastaging.launchpad.net/qastaging/launchpad-rev-11738/eggs/Twisted-10.1.0-py2.6-linux-x86_64.egg/twisted/scripts/_twistd_unix.py", line 139, in _getLogObserver
    logFile = logfile.LogFile.fromFullPath(self._logfilename)
  File "/srv/bazaar.qastaging.launchpad.net/qastaging/launchpad-rev-11738/eggs/Twisted-10.1.0-py2.6-linux-x86_64.egg/twisted/python/logfile.py", line 49, in fromFullPath
    os.path.dirname(logPath), *args, **kwargs)
  File "/srv/bazaar.qastaging.launchpad.net/qastaging/launchpad-rev-11738/eggs/Twisted-10.1.0-py2.6-linux-x86_64.egg/twisted/python/logfile.py", line 162, in __init__
    BaseLogFile.__init__(self, name, directory, defaultMode)
  File "/srv/bazaar.qastaging.launchpad.net/qastaging/launchpad-rev-11738/eggs/Twisted-10.1.0-py2.6-linux-x86_64.egg/twisted/python/logfile.py", line 34, in __init__
    assert os.path.isdir(self.directory)
AssertionError
.

The assertion can be improved but it would be nice to have a preflight check that this problem doesn't exist (for use before we shutdown services to start a bait-and-switch deployment).

[Aaron Bentley (abentley)]

I don't know what a preflight check is, but it sounds like look before you leap. It would make sense to have a way to create all necessary directories, and it would make sense to have a sane error message if we don't have the necessary log file directory, but do we really need a preflight check?

[Gary Poster (gary)]

I'm afraid I don't have enough context as to what Twisted bits "bzr-sftp-qastaging start" is running. Could someone clarify?

[Robert Collins (lifeless)]

On production, the user running as a daemon may well not have
permission to create the directories we need; so having something to
create those directories won't assist with this case.

Yes, its a form of LBYL, but its one of the cases where it makes sense, I think.

[Tom Haddon (mthaddon)]

https://pastebin.canonical.com/38893/ is the initscript