[Bug 1251257] Re: [SRU] avahi fails in containers

[Launchpad Bug Tracker]

** Branch linked: lp:ubuntu/saucy-proposed/avahi

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https://bugs.launchpad.net/bugs/1251257

Title:
  [SRU] avahi fails in containers

Status in MAAS:
  Triaged
Status in MAAS 1.4 series:
  Triaged
Status in “avahi” package in Ubuntu:
  Fix Released
Status in “avahi” source package in Saucy:
  Fix Committed
Status in “avahi” source package in Trusty:
  Fix Released

Bug description:
  installed a brand new maas server on suacy into an lxc container from
  archive and http://<ip>/MAAS is not accessible although http://<ip> is
  accessible

  http://<ip>/MAAS is getting logged to /var/log/apache2/access.log
  though so request is making it through

  <roaksoax> danwest: can you please pastebin apache2's error and access.log
  <danwest> http://paste.ubuntu.com/6405411/
  <danwest> http://paste.ubuntu.com/6405412/

  <roaksoax> danwest: I know what it is
  <roaksoax> danwest: dbus/avahi
  <roaksoax> danwest: try to restart whatever avahi service there is
  <andreas> "dbus" reminds me of https://bugs.launchpad.net/juju-core/+bug/1248283
  <andreas> but that was about the units, not maas itself
  <danwest> https://pastebin.canonical.com/100290/
  <danwest> same problem
  <roaksoax> danwest: yeah the avahi daemon is failing to start, causing maas to fail
  <roaksoax> danwest: maybe restart whatever dbus serviice it is, and then the avahi-daemon
  <matsubara> danwest, restart dbus and avahi-daemon, see https://bugs.launchpad.net/maas/+bug/1221059

  <roaksoax> danwest: did avahi-daemon restart corrrectly?
  <danwest> nope
  <roaksoax> danwest: i guess then an issue with dbus is preventing avahi from working... hence maas failing
  <danwest> roaksoax: should not matter but the only thing that is a little unique is that this is in a saucy container

  <roaksoax> danwest: ah so then thats the issue...
  <danwest> what, the container?
  <roaksoax> yeah
  <danwest> how so?
  <roaksoax> avahi might have issues running in a container

  <danwest> hallyn: roaksoax: what should I file that lxc/avahi /maas bug that I hit this morning against?
  <hallyn> danwest: i think maas should work around it by unsetting rlimit-nproc
  <hallyn> (and/or by running on trusty in a private user ns

  <hallyn> smoser: fwiw the problem is that avahi sets its nproc rlimit to exaclty 3, but in a container it's using a uid that is in use on the host - so it exceeds 3 tasks
  <hallyn> (i.e. it's reusing uid which is ntp on the host, and ntp is running;  or just another avahi)
  <smoser> ok...
  <smoser> so that doesn't seem like maas's problem to me
  <smoser> nor juju's really.
  <hallyn> smoser: it is.  it needs to pick a unique uid, or configure avahi to ignore the rlimit
  <smoser> maas isn't running avahi
  <smoser> is it ?
  <hallyn> i duno what's actually running it :)  it's *for* maas, but it probably is juju
  <smoser> what if there was a bug in php, and a user used maas to deploy php.
  <smoser> should we fix that in maas ?
  <hallyn> you're talking about a bug.  i'm talking about a resource conflict
  <hallyn> having avahi alwasy run without nprocs, for protection, would be wrong for this.

  fix is still up for debate on this one...

  [Impact]
  Avahi sets the rlimit_nproc to 3, causing avahi to fail running in containers. This This option should not be set in containers at all. This causes avahi-daemon to fail, hence all the applications that use avahi will also fail. In this particular case, MAAS fails because of this.

  [Test Case]
  1. Install a container.
  2. Install MAAS
  3. Check apache2 log for errors, such as those in [1].

  [Regression Potential]
  Minimal. This has been tested and works as expected.

  [1]: http://paste.ubuntu.com/6405412/

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