[Bug 1578080] Re: percona cluster hits resource limits in HA Openstack cloud with xenial

[Launchpad Bug Tracker]

This bug was fixed in the package systemd - 229-4ubuntu6

---------------
systemd (229-4ubuntu6) xenial-proposed; urgency=medium

  * Add a DHCP exit hook for pushing received NTP servers into timesyncd.
    (LP: #1578663)
  * Revert "enable TasksMax= for all services by default, and set it to 512".
    Introducing a default limit on number of threads broke a lot of software
    which regularly needs more, such as MySQL and RabbitMQ, or services that
    spawn off an indefinite number of subtasks that are not in a scope, like
    LXC or cron. 512 is way too much for most "simple" services, and it's way
    too little for the ones mentioned above. Effective (and much stricter)
    limits should instead be put into units individually.
    (Closes: #823530, LP: #1578080)
  * debian/gbp.conf: Switch to ubuntu-xenial branch.

 -- Martin Pitt <martin.pitt at ubuntu.com>  Thu, 12 May 2016 10:39:30
+0200

** Changed in: systemd (Ubuntu Xenial)
       Status: Fix Committed => Fix Released

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https://bugs.launchpad.net/bugs/1578080

Title:
  percona cluster hits resource limits in HA Openstack cloud with xenial

Status in percona-xtradb-cluster-5.6 package in Ubuntu:
  Won't Fix
Status in systemd package in Ubuntu:
  Fix Released
Status in systemd source package in Xenial:
  Fix Released
Status in percona-cluster package in Juju Charms Collection:
  Won't Fix
Status in systemd package in Debian:
  Fix Released

Bug description:
  I'm trying to deploy Mitaka Openstack using the 16.04 charms on Xenial
  using Juju 1.25.5 and MAAS 1.9.2, with as many components of Openstack
  being HA as possible.

  When deployed, after running for a while mysql (which is a 3 node
  cluster) starts refusing connections, and erroring:

    2016-05-03 01:25:28 13795 [ERROR] Error log throttle:         50
  'Can't create thread to handle new connection' error(s) suppressed

  When I look at systemd-cgtop, I can see it maxing out at 512
  connections.

  To get it going again I do a:

    $ sudo systemctl edit mysql

  and set:

    TasksMax=infinity

  Sometimes I even need to edit /etc/systemd/system.conf and bump
  DefaultTasksMax to 1024 or higher, depending on long its been left
  running.

  I've noticed that dropping worker-multiplier setting on nova-cloud-
  controller, neutron-api etc all help to reduce the load, but I still
  need to bump it up.

  Please let me know if you need any more information.

  SRU INFORMATION
  ---------------
  Impact: Introducing a default #thread limit of 512 broke an unknown set of services which regularly run many threads.
  Fix: http://anonscm.debian.org/cgit/pkg-systemd/systemd.git/commit/?id=fe4d9d3ba0 (essentially, revert the upstream commit that enabled it)
  Regression potential: Very low -- this just restores the pre-228 behaviour and does not impose any new restriction.
  Test case:
   - Pick some unit like cron.service or mysql.service that does not specify an explicit TaskMax= limit.
   - Check its TaskMax: systemctl show -p TasksMax cron.service
   - In current xenial this is "512", after the update it should be a very big number (maxint minus 1, which means "infinity")

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