[Bug 1969162] Re: bad interaction between snapd and update-notifier when snapd package is being upgraded

[Michael Vogt]

I ran the spread test in the snapd PR
https://github.com/snapcore/snapd/pull/11702 against this change in
21.10 and 22.04 and the restart behavior is correct: if snapd is
upgraded from a version that does not yet use "dh_systemd --restart-
after-upgrade" still keep running.

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

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https://bugs.launchpad.net/bugs/1969162

Title:
  bad interaction between snapd and update-notifier when snapd package
  is being upgraded

Status in snapd package in Ubuntu:
  Fix Committed
Status in update-notifier package in Ubuntu:
  Invalid
Status in snapd source package in Impish:
  Fix Committed

Bug description:
  [Impact]

  On a release upgrade from impish to jammy, dbus postinst hangs for 10
  minutes.

  [Test Case]

  Testing the fix itself:

  On a minimal impish system (created with autopkgtest-buildvm), install the snapd from -proposed and run:
  $ sudo snap install canonical-livepatch
  $ apt list -a snapd
  [shows the impish proposed version is used]
  $ sudo sed -i 's/impish/jammy/' /etc/apt/sources.list
  $ sudo apt update
  $ apt list -a snapd
  [shows the PPA version as the one that will be upgraded to]
  $ sudo apt full-upgrade -y

  This should pass

  Another test would be simply trying an upgrade from impish to jammy as
  per the original report.

  [Regression Potential]

  TBD

  [Original Description]

  On a release upgrade from impish to jammy, I noticed that the dbus
  postinst hung for 10 minutes.  It hung trying to make two calls to
  canonical-livepatch via /usr/share/update-notifier/notify-reboot-
  required: first a call to /snap/bin/canonical-livepatch kernel-
  upgrade-required which hung for ~5 minutes, then a call to
  /snap/bin/canonical-livepatch status which hung for another ~5
  minutes.

  An strace of the second process showed that canonical-livepatch was
  looping trying to connect to /run/snapd.socket:

  [pid 769177] connect(3, {sa_family=AF_UNIX,
  sun_path="/run/snapd.socket"}, 20) = -1 ECONNREFUSED (Connection
  refused)

  This was not attached to anything, because the snapd package was among
  those in the current apt transaction, and was currently not in a
  configured state:

  root      756701  0.0  0.0  24144 12556 pts/20   Ss+  17:26   0:00  |
  |               \_ /usr/bin/dpkg --force-overwrite --status-fd 57
  --no-triggers --configure apparmor:amd64 openssl:amd64 ca-
  certificates:all libmd0:amd64 libmd0:i386 libbsd0:amd64 libbsd0:i386
  libedit2:amd64 libtinfo6:i386 libedit2:i386 libcbor0.8:amd64
  libfido2-1:amd64 libkrb5support0:amd64 libkrb5-3:amd64 libgssapi-
  krb5-2:amd64 openssh-client:amd64 liblzo2-2:amd64 squashfs-tools:amd64
  libcap2:amd64 libkmod2:amd64 udev:amd64 libapparmor1:amd64
  libapparmor1:i386 libdbus-1-3:amd64 libcap2:i386 libzstd1:i386
  libsystemd0:i386 libdbus-1-3:i386 dbus:amd64 libpam-systemd:amd64
  dbus-user-session:amd64 snapd:amd64

  iU  snapd          2.55.3+22.04 amd64        Daemon and tooling that
  enable snap packages

  This should probably be fixed by not stopping snapd in the prerm
  (dh_systemd_start --restart-after-upgrade).

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