[Bug 1693361] Re: cloud-init sometimes fails on dpkg lock due to concurrent apt-daily.service execution

[Julian Andres Klode]

We eventually want wait locking in apt, but I don't think it really
solves all issues, especially in scripts with multiple apt invocations.
Which is why apt-daily got an additional flock lock for the upcoming
SRUs. (see artful).

Feel free.to wait on the same.lock and probably add some ordering
against apt-daily and apt-daily-upgrade services.

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https://bugs.launchpad.net/bugs/1693361

Title:
  cloud-init sometimes fails on dpkg lock due to concurrent apt-
  daily.service execution

Status in APT:
  Unknown
Status in cloud-init:
  Confirmed
Status in apt package in Ubuntu:
  New
Status in cloud-init package in Ubuntu:
  Confirmed
Status in cloud-init source package in Xenial:
  Confirmed
Status in cloud-init source package in Yakkety:
  Confirmed
Status in cloud-init source package in Zesty:
  Confirmed
Status in cloud-init source package in Artful:
  Confirmed

Bug description:
  apt-daily is now a systemd service rather than being invoked by
  cron.daily.  If one builds a custom AMI it is possible that the apt-
  daily.timer will fire during boot.  This can fire at the same time
  cloud-init is running and if cloud-init loses the race the invocation
  of apt (e.g. use of "packages:" in the config) will fail.

  There is a lot of discussion online about this change to apt-daily
  (e.g. unattended upgrades happening during business hours, delaying
  boot, etc.) and discussion of potential systemd changes regarding
  timers firing during boot (c.f.
  https://github.com/systemd/systemd/issues/5659).

  While it would be better to solve this in apt itself, I suggest that
  cloud-init be defensive when calling apt and implement some retry
  mechanism.

  Various instances of people running into this issue:

  https://github.com/chef/bento/issues/609
  https://clusterhq.atlassian.net/browse/FLOC-4486
  https://github.com/boxcutter/ubuntu/issues/73
  https://unix.stackexchange.com/questions/315502/how-to-disable-apt-daily-service-on-ubuntu-cloud-vm-image

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