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

[Martin Pitt]

Upstream report: https://github.com/systemd/systemd/issues/3211

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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:
  In Progress
Status in systemd source package in Xenial:
  In Progress
Status in percona-cluster package in Juju Charms Collection:
  New
Status in systemd package in Debian:
  Unknown

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.

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