rolling update logic compares str(template)

[Christopher Armstrong]

When the rolling update code determines which instances are "being updated" (and thus need temporarily removed from the load balancer), it tries to compare the str() of a template dict. Unfortunately, str() of dicts in Python does not have a reliable ordering, so this logic can erroneously determine that some instances are being updated when they are not.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/68311

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/68311
Committed: https://git.openstack.org/cgit/openstack/heat/commit/?id=d3d4c72a0291412348c4d9d55b038e67ad30e2ba
Submitter: Jenkins
Branch: master

commit d3d4c72a0291412348c4d9d55b038e67ad30e2ba
Author: Christopher Armstrong <email address hidden>
Date: Wed Jan 22 03:22:43 2014 +0000

    Make LB-updating in rolling update more reliable

    The rolling update code updates the load balancer when instances
    are being updated (and thus out of service). It determines which instances
    are being changed by comparing the str() of the templates. Unfortunately,
    str() of dicts in Python returns keys in an unreliable order, depending on
    the way the dicts were constructed. Therefore, sometimes rolling updates
    would erroneously determine that instances were changing when they were not,
    and take them out of service in the load balancer.

    This patch contains no additional tests because it's not really possible to
    reliably reproduce this across multiple platforms. Existing tests will fail if
    the erroneous case is triggered.

    Change-Id: Icb564a65ca118a2fc84d7df8c44330281074bbb7
    Closes-Bug: #1271397