Comment 5 for bug 1389782

Reviewed: https://review.openstack.org/133479
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=afe86b6f29033a472cab1b52dd0724bb3c6dfb82
Submitter: Jenkins
Branch: master

commit afe86b6f29033a472cab1b52dd0724bb3c6dfb82
Author: Michal Dulko <email address hidden>
Date: Wed Feb 4 12:44:12 2015 +0100

    Fix conductor servicegroup joining when zk driver is used

    When conductor is run as multiprocess (default for multi core system) and
    zk (zookeeper) is used as servicegroup_driver then conductor is unable to join
    servicegroup because of shared zookeeper handle (and probably socket)
    between parent and children processes.

    It's found the problem lies in zookeeper c library implementation.
    Proof can be seen in related bug #1389782.

    This fix follows the idea used by memcache and db driver that
    servicegroup_api._driver object is used in lazy manner.
    This means that like connection to memcache and session to database,
    zookeeper handle (zk session in driver) isn't created until required by
    worker (child process).

    Additional note: before fix, during Service object creation the
    prefix in zookeeper was created. That was the probably reason the session was
    established so early. In my opinion the eagerness of this is not necessary
    and namespace can be created by child process as well.

    Closes-Bug: #1389782

    Related-bug: #1390511
    Related-bug: #1382153

    Change-Id: I9b386ef1f9268d19d04879ec89e5684170f3862a