[Bug 1906617] Re: Anacron prevents shutdown while a job is running. Some packages install long-running jobs.

[Launchpad Bug Tracker]

Status changed to 'Confirmed' because the bug affects multiple users.

** Changed in: mlocate (Ubuntu)
       Status: New => Confirmed

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https://bugs.launchpad.net/bugs/1906617

Title:
  Anacron prevents shutdown while a job is running. Some packages
  install long-running jobs.

Status in anacron package in Ubuntu:
  Confirmed
Status in mlocate package in Ubuntu:
  Confirmed

Bug description:
  I encountered this issue with Anacron and the mlocate package. One of
  the daily jobs which mlocate installs is a job which runs
  `updatedb.mlocate` to update its search index. This job goes through
  the entire filesystem tree, which, as you would expect, can be a
  fairly long-running process.

  When the system shuts down, anacron is sent a SIGUSR1 signal,
  indicating a graceful shutdown; anacron will exit, but only after all
  tasks are done. Since one of the daily tasks is long-running, the task
  likely won't finish within the 90 second window provided by systemd.
  This means that, fairly often, my shutdowns are delayed by 90 seconds
  for no good reason; nothing would break if the updatedb.mlocate job
  was interrupted, and it's going to be interrupted anyways once its 90
  seconds are up.

  Personally, I think the best solution here is to somehow get Anacron
  to send a SIGTERM signal to its jobs when the system shuts down. This
  would delegate responsibility to the job itself. A super critical job
  which _has_ to complete before shutdown could catch the SIGTERM signal
  and cleanly exit, while other jobs which don't really care (such as
  updatedb.mlocate) could just terminate in response to SIGTERM.

  The alternative solution would be to ensure that no package will ever
  install a potentially long-running cron job. I don't know how
  realistic this is. The mlocate package, for example, would find some
  other way to periodically trigger an updatedb in a way which doesn't
  block shutdown (it could, for example, install a systemd timer instead
  of a cron job).

  As a partial solution, one should consider adding some logging to
  anacron, which makes it print messages like "Waiting for <job name> to
  shut down..." so that the issue can be debugged. I would've been much
  less frustrated by this issue over the past few months if the message
  I saw while shutting down was "anacron: Waiting for job mlocate to
  terminate..." rather than just "A stop job is running for Run anacron
  jobs".

  I want to clarify that this isn't "just" an issue with mlocate, but an
  issue with every package which uses cron jobs to run potentially long
  running jobs. Fixing the mlocate package would treat the particular
  symptom I'm experiencing, but I'm sure there are many other packages
  which install potentially long running cron jobs.

  ProblemType: Bug
  DistroRelease: Ubuntu 20.10
  Package: anacron 2.3-29
  ProcVersionSignature: Ubuntu 5.8.0-31.33-generic 5.8.17
  Uname: Linux 5.8.0-31-generic x86_64
  NonfreeKernelModules: nvidia_modeset nvidia
  ApportVersion: 2.20.11-0ubuntu50.2
  Architecture: amd64
  CasperMD5CheckResult: skip
  CurrentDesktop: ubuntu:GNOME
  Date: Thu Dec  3 09:01:15 2020
  InstallationDate: Installed on 2019-09-14 (445 days ago)
  InstallationMedia: Ubuntu 19.04 "Disco Dingo" - Release amd64 (20190416)
  SourcePackage: anacron
  UpgradeStatus: Upgraded to groovy on 2020-09-05 (88 days ago)

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