[Bug 1518430] Related fix merged to oslo.messaging (master)

[OpenStack Infra]

Reviewed:  https://review.opendev.org/558882
Committed: https://git.openstack.org/cgit/openstack/oslo.messaging/commit/?id=d873c0d8f5722d5e2a08b5fc49d58b63dbe061a0
Submitter: Zuul
Branch:    master

commit d873c0d8f5722d5e2a08b5fc49d58b63dbe061a0
Author: John Eckersberg <jeckersb at redhat.com>
Date:   Wed Apr 4 12:55:44 2018 -0400

    Do not use threading.Event
    
    Waiting on a threading.Event with eventlet can cause busy looping via
    epoll_wait, see related bug for more details.
    
    Change-Id: I007613058a2d21d1712c02fa6d1602b63705c1ab
    Related-bug: #1518430

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https://bugs.launchpad.net/bugs/1518430

Title:
  liberty: ~busy loop on epoll_wait being called with zero timeout

Status in Ubuntu Cloud Archive:
  Fix Committed
Status in Ubuntu Cloud Archive kilo series:
  Fix Committed
Status in Ubuntu Cloud Archive liberty series:
  Fix Released
Status in Ubuntu Cloud Archive mitaka series:
  Fix Released
Status in Ubuntu Cloud Archive newton series:
  Fix Released
Status in oslo.messaging:
  Fix Released
Status in python-oslo.messaging package in Ubuntu:
  Fix Released
Status in python-oslo.messaging source package in Xenial:
  Fix Released
Status in python-oslo.messaging source package in Yakkety:
  Fix Released
Status in python-oslo.messaging source package in Zesty:
  Fix Released

Bug description:
  Context: openstack juju/maas deploy using 1510 charms release
  on trusty, with:
    openstack-origin: "cloud:trusty-liberty"
    source: "cloud:trusty-updates/liberty

  * Several openstack nova- and neutron- services, at least:
  nova-compute, neutron-server, nova-conductor,
  neutron-openvswitch-agent,neutron-vpn-agent
  show almost busy looping on epoll_wait() calls, with zero timeout set
  most frequently.
  - nova-compute (chose it b/cos single proc'd) strace and ltrace captures:
    http://paste.ubuntu.com/13371248/ (ltrace, strace)

  As comparison, this is how it looks on a kilo deploy:
  - http://paste.ubuntu.com/13371635/

  * 'top' sample from a nova-cloud-controller unit from
     this completely idle stack:
    http://paste.ubuntu.com/13371809/

  FYI *not* seeing this behavior on keystone, glance, cinder,
  ceilometer-api.

  As this issue is present on several components, it likely comes
  from common libraries (oslo concurrency?), fyi filed the bug to
  nova itself as a starting point for debugging.

  Note: The description in the following bug gives a good overview of
  the issue and points to a possible fix for oslo.messaging:
  https://bugs.launchpad.net/mos/+bug/1380220

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