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[Brian Murray <1870087@xxxxxxxxxxxxxxxxxx>]

Hello Mark, or anyone else affected,

Accepted landscape-client into groovy-proposed. The package will build
now and be available at https://launchpad.net/ubuntu/+source/landscape-
client/19.12-0ubuntu5.1 in a few hours, and then in the -proposed
repository.

Please help us by testing this new package.  See
https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how
to enable and use -proposed.  Your feedback will aid us getting this
update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug,
mentioning the version of the package you tested, what testing has been
performed on the package and change the tag from verification-needed-
groovy to verification-done-groovy. If it does not fix the bug for you,
please add a comment stating that, and change the tag to verification-
failed-groovy. In either case, without details of your testing we will
not be able to proceed.

Further information regarding the verification process can be found at
https://wiki.ubuntu.com/QATeam/PerformingSRUVerification .  Thank you in
advance for helping!

N.B. The updated package will be released to -updates after the bug(s)
fixed by this package have been verified and the package has been in
-proposed for a minimum of 7 days.

** Changed in: landscape-client (Ubuntu Groovy)
       Status: In Progress => Fix Committed

** Tags removed: verification-done
** Tags added: verification-needed verification-needed-groovy

** Changed in: landscape-client (Ubuntu Focal)
       Status: In Progress => Fix Committed

** Tags removed: verification-done-focal
** Tags added: verification-needed-focal

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https://bugs.launchpad.net/bugs/1870087

Title:
  Old broker lockfile blocks landscape-client starts

Status in Landscape Client:
  In Progress
Status in landscape-client package in Ubuntu:
  Fix Released
Status in landscape-client source package in Focal:
  Fix Committed
Status in landscape-client source package in Groovy:
  Fix Committed

Bug description:
  [Impact]

   * landscape-client services are prevented from starting if its older PIDs get
     recycled.

   * The exact conditions for the issue, are particularly more likely to occur
     on release upgrade. This is exacerbated by the fact clients did not await
     on their shutdown routine, thus were likely to leak their lock file.

   * The proposed fix tries to verify existing locks actually belong
     to landscape-client, instead of just verifying they exist.

   * The follow-up patch ensured some of the process actually complete
  their shutdown.

  [Test Case]

   * systemctl stop landscape-client

   * There should not be any remaining file in
  /var/lib/landscape/client/sockets/

   * ln -sf 1 /var/lib/landscape/client/sockets/broker.sock.lock

   * systemctl start landscape-client

  [Regression Potential]

   * The existing twisted logic is still kept, so assuming checking process
     names fail, lock conflicts should still be detected normally.

   * The locks which twisted creates are unlikely to actually see conflicts in
     the wild as those processes are managed by systemd. False positives in
     the detection check should have minimal impact.

  [Original description]

  I have a machine which was failing to connect to the landscape
  service. In syslog I found this traceback:

  Apr  1 03:27:53 maas-1 landscape-client[1538354]: Traceback (most recent call last):
  Apr  1 03:27:53 maas-1 landscape-client[1538354]:   File "/usr/lib/python3/dist-packages/twisted/python/lockfile.py", line 160, in lock
  Apr  1 03:27:53 maas-1 landscape-client[1538354]:     symlink(str(os.getpid()), self.name)
  Apr  1 03:27:53 maas-1 landscape-client[1538354]: FileExistsError: [Errno 17] File exists: '1538397' -> b'/var/lib/landscape/client/sockets/broker.sock.lock'
  Apr  1 03:27:53 maas-1 landscape-client[1538354]: During handling of the above exception, another exception occurred:
  Apr  1 03:27:53 maas-1 landscape-client[1538354]: Traceback (most recent call last):
  Apr  1 03:27:53 maas-1 landscape-client[1538354]:   File "/usr/bin/landscape-broker", line 8, in <module>
  Apr  1 03:27:53 maas-1 landscape-client[1538354]:     run(sys.argv)
  Apr  1 03:27:53 maas-1 landscape-client[1538354]:   File "/usr/lib/python3/dist-packages/landscape/client/broker/service.py", line 93, in run
  Apr  1 03:27:53 maas-1 landscape-client[1538354]:     run_landscape_service(BrokerConfiguration, BrokerService, args)
  Apr  1 03:27:53 maas-1 landscape-client[1538354]:   File "/usr/lib/python3/dist-packages/landscape/client/service.py", line 115, in run_landscape_service
  Apr  1 03:27:53 maas-1 landscape-client[1538354]:     startApplication(application, False)
  Apr  1 03:27:53 maas-1 landscape-client[1538354]:   File "/usr/lib/python3/dist-packages/twisted/application/app.py", line 690, in startApplication
  Apr  1 03:27:53 maas-1 landscape-client[1538354]:     service.IService(application).startService()
  Apr  1 03:27:53 maas-1 landscape-client[1538354]:   File "/usr/lib/python3/dist-packages/twisted/application/service.py", line 288, in startService
  Apr  1 03:27:53 maas-1 landscape-client[1538354]:     service.startService()
  Apr  1 03:27:53 maas-1 landscape-client[1538354]:   File "/usr/lib/python3/dist-packages/landscape/client/broker/service.py", line 79, in startService
  Apr  1 03:27:53 maas-1 landscape-client[1538354]:     self.publisher.start()
  Apr  1 03:27:53 maas-1 landscape-client[1538354]:   File "/usr/lib/python3/dist-packages/landscape/client/amp.py", line 45, in start
  Apr  1 03:27:53 maas-1 landscape-client[1538354]:     self._port = self._reactor.listen_unix(socket_path, factory)
  Apr  1 03:27:53 maas-1 landscape-client[1538354]:   File "/usr/lib/python3/dist-packages/landscape/lib/reactor.py", line 228, in listen_unix
  Apr  1 03:27:53 maas-1 landscape-client[1538354]:     return self._reactor.listenUNIX(socket, factory, wantPID=True)
  Apr  1 03:27:53 maas-1 landscape-client[1538354]:   File "/usr/lib/python3/dist-packages/twisted/internet/posixbase.py", line 397, in listenUNIX
  Apr  1 03:27:53 maas-1 landscape-client[1538354]:     p.startListening()
  Apr  1 03:27:53 maas-1 landscape-client[1538354]:   File "/usr/lib/python3/dist-packages/twisted/internet/unix.py", line 372, in startListening
  Apr  1 03:27:53 maas-1 landscape-client[1538354]:     if not self.lockFile.lock():
  Apr  1 03:27:53 maas-1 landscape-client[1538354]:   File "/usr/lib/python3/dist-packages/twisted/python/lockfile.py", line 185, in lock
  Apr  1 03:27:53 maas-1 landscape-client[1538354]:     kill(int(pid), 0)
  Apr  1 03:27:53 maas-1 landscape-client[1538354]: PermissionError: [Errno 1] Operation not permitted

  In the sockets directory I saw:

  $ sudo ls /var/lib/landscape/client/sockets/ -la
  total 8
  drwxr-x--- 2 landscape root      4096 Apr  1 03:27 .
  drwxr-xr-x 7 landscape root      4096 Apr  1 03:27 ..
  srw-rw-rw- 1 landscape landscape    0 Mar 12 01:41 broker.sock
  lrwxrwxrwx 1 landscape landscape    3 Mar 12 01:41 broker.sock.lock -> 905

  Removing those two files allowed the landscape client to start as
  normal.

  Looks like we need some lockfile cleanup code on start.

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