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

Martin Pitt martin.pitt at ubuntu.com
Mon May 23 13:36:48 UTC 2016

> Will my systemd scripts with TasksMax setting keep working?

Yes, this only changes the builtin defaults if there is no explicit
TaskMax= setting.

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  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

  To get it going again I do a:

    $ sudo systemctl edit mysql

  and set:


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

  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.

  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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