group.of.nepali.translators team mailing list archive

[Robie Basak <1761096@xxxxxxxxxxxxxxxxxx>]

On Xenial the source package is squid3, not squid, so I'll add/adjust
tasks for that so the tracking works correctly.

On Bionic the code suggests that the same problem might exist, but it
appears that nobody has reproduced it there so there is no need for an
SRU to Bionic. However, if somebody is affected then we can look again.
I'll leave an Incomplete task for Bionic to try to highlight that. We
don't have any specific policy or pattern to track this kind of thing so
I'm being inventive with the bug status here.

Excerpts from #ubuntu-devel:

17:32 <rbasak> cpaelzer, sergiodj: in bug 1761096, did you ever find out
why Bionic are unaffected, or did you decide it wasn't worth
investigating further?

17:32 <rbasak> *is*

17:38 <sergiodj> rbasak: we could not find exactly why Bionic is not
affected.  my hypothesis is that between Xenial and Bionic there was a
fix on systemd which addressed this issue, but I could not pinpoint
exactly what was done

17:39 <sergiodj> arguably, the best scenario would be to backport this
fix to Xenial's systemd, but since we had already spent a non-trivial
amount of time investigating this (without finding anything concrete on
systemd's side), I opted for the second best thing to do, which is to
use --no-block to workaround this bug


** Also affects: squid3 (Ubuntu)
   Importance: Undecided
       Status: New

** Also affects: squid (Ubuntu Bionic)
   Importance: Undecided
       Status: New

** Also affects: dnsmasq (Ubuntu Bionic)
   Importance: Undecided
       Status: New

** Also affects: squid3 (Ubuntu Bionic)
   Importance: Undecided
       Status: New

** Changed in: squid3 (Ubuntu)
       Status: New => Invalid

** Changed in: squid3 (Ubuntu Bionic)
       Status: New => Incomplete

** Changed in: squid3 (Ubuntu Xenial)
       Status: New => In Progress

** Changed in: squid3 (Ubuntu Xenial)
     Assignee: (unassigned) => Sergio Durigan Junior (sergiodj)

** Changed in: squid (Ubuntu Xenial)
     Assignee: Sergio Durigan Junior (sergiodj) => (unassigned)

** Changed in: squid (Ubuntu Xenial)
   Importance: High => Undecided

** Changed in: squid (Ubuntu Xenial)
       Status: Confirmed => Invalid

** Changed in: squid (Ubuntu Bionic)
       Status: New => Invalid

** Changed in: squid3 (Ubuntu Xenial)
   Importance: Undecided => High

** Changed in: dnsmasq (Ubuntu Bionic)
       Status: New => Invalid

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https://bugs.launchpad.net/bugs/1761096

Title:
  dnsmasq starts with error on Ubuntu Xenial amd64 when squid installed

Status in dnsmasq package in Ubuntu:
  Fix Released
Status in squid package in Ubuntu:
  Fix Released
Status in squid3 package in Ubuntu:
  Invalid
Status in dnsmasq source package in Xenial:
  Invalid
Status in squid source package in Xenial:
  Invalid
Status in squid3 source package in Xenial:
  Fix Committed
Status in dnsmasq source package in Bionic:
  Invalid
Status in squid source package in Bionic:
  Invalid
Status in squid3 source package in Bionic:
  Incomplete

Bug description:
  [Impact]

  When using dnsmasq along with squid on Ubuntu Xenial, the user will
  experience a deadlock while performing on every second execution of
  the "systemctl start dnsmasq.service" command.  The deadlock will be
  caused by an attempt to invoke, by nss-lookup.target, a "systemctl
  reload squid.service", which will itself try to start the nss-
  lookup.target, which will be waiting on squid, therefore eventually
  leading to a timeout.

  The underlying cause of this deadlock is related to how systemd used
  to handle dependencies between multiple jobs being started in the same
  transaction.

  [Test Case]

  One can reproduce the issue on a Xenial container:

  $ lxc launch ubuntu-daily:xenial squid-bug1761096
  $ lxc shell squid-bug1761096
  # apt update
  # apt install squid dnsmasq -y

  It is quite possible that during "apt install" the bug will manifest,
  and dnsmasq will fail to start due to a timeout.  The user might see a
  message like:

  Job for dnsmasq.service failed because a timeout was exceeded. See
  "systemctl status dnsmasq.service" and "journalctl -xe" for details.

  If the bug doesn't manifest itself during installation, the following
  commands in sequence should trigger it:

  # systemctl restart dnsmasq.service
  # systemctl restart dnsmasq.service

  [Regression Potential]

  This change only touches the mechanism by which squid has its
  configuration reloaded in case of a DNS resolver change.  Because
  "systemctl reload --no-block" returns practically immediately, if
  squid's configuration file is invalid the user won't see any
  notifications.  However, this behaviour is already present currently,
  because "systemctl reload squid" invokes "/etc/init.d/squid reload";
  the user has to check "journalctl -u squid.service" if she wants to
  verify whether there were any failures during the reload.

  Other than that, and because systemctl will offload the service to the
  SysV script as usual (in the case of squid), I don't foresee any
  potential regressions.

  [Original Description]

  Setup to reproduce:

  Ubuntu Xenial amd64 net install iso from
  http://archive.ubuntu.com/ubuntu/dists/xenial/main/installer-
  amd64/current/images/netboot/mini.iso

  Install system with mostly defaults + LVM + OpenSSH server

  Note that this bug applies to both DHCP and static IP+DNS network
  configurations

  Once server rebooted and is available, log in and install dnsmasq + squid:
  apt-get update && apt-get install squid dnsmasq

  output of this can be found at https://pastebin.com/9Atuipju
  journalctl -xe output at https://pastebin.com/uLhfM4jN

  Furthermore at this point I can run alternating errors

  root@ubuntu-min:~# date ; service dnsmasq start ; date
  Wed Apr  4 09:18:07 CEST 2018
  Wed Apr  4 09:18:07 CEST 2018
  root@ubuntu-min:~# date ; service dnsmasq stop ; date
  Wed Apr  4 09:18:39 CEST 2018
  Wed Apr  4 09:18:39 CEST 2018
  root@ubuntu-min:~# date ; service dnsmasq start ; date
  Wed Apr  4 09:19:10 CEST 2018
  Job for dnsmasq.service failed because a timeout was exceeded. See "systemctl status dnsmasq.service" and "journalctl -xe" for details.
  Wed Apr  4 09:20:40 CEST 2018
  root@ubuntu-min:~# date ; service dnsmasq start ; date
  Wed Apr  4 09:42:57 CEST 2018
  Wed Apr  4 09:42:57 CEST 2018
  root@ubuntu-min:~# date ; service dnsmasq stop ; date
  Wed Apr  4 09:43:14 CEST 2018
  Wed Apr  4 09:43:14 CEST 2018
  root@ubuntu-min:~# date ; service dnsmasq start ; date
  Wed Apr  4 09:43:26 CEST 2018
  Job for dnsmasq.service failed because a timeout was exceeded. See "systemctl status dnsmasq.service" and "journalctl -xe" for details.
  Wed Apr  4 09:44:56 CEST 2018

  and so on... Each and every 1 out of 2 stop/start cycle fails in 1m30s
  timeout

  Complete journalctl -xe output attached

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