Comment 16 for bug 1533787

Reviewed: https://review.openstack.org/272693
Committed: https://git.openstack.org/cgit/openstack/ceilometer/commit/?id=67e47cda8e7e0d2649fef334a6e0db2826d5fbd1
Submitter: Jenkins
Branch: stable/liberty

commit 67e47cda8e7e0d2649fef334a6e0db2826d5fbd1
Author: gordon chung <email address hidden>
Date: Thu Jan 14 09:47:33 2016 -0500

    better support notification coordination

    when launching multiple agents at same time, there is a chance that
    agents will miss the registry of another agent. this is possible
    because there is a lot of overhead involved when starting up agents,
    specifically with initialising managers.

    this change makes it so the agent only joins the group AFTER it has
    done all setup that does not require coordination. after it joins,
    we start listening right away for other changes to group membership

    additionally, this adds a lock to pipeline queue setup so only one
    event at any time can trigger a reconfiguration.

    Change-Id: I8100160a3aa83a190c4110e6e8be9b26aef8fd1c
    Closes-Bug: #1533787