Comment 4 for bug 1423648

Reviewed: https://review.openstack.org/162746
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=36a703516251c7268ebceb414ed71e4cab4794b0
Submitter: Jenkins
Branch: master

commit 36a703516251c7268ebceb414ed71e4cab4794b0
Author: Chris Friesen <email address hidden>
Date: Mon Mar 16 09:35:16 2015 -0600

    Validate server group affinity policy

    In git commit a79ecbe Russell Bryant submitted a partial fix for a race
    condition when booting an instance as part of a server group with an
    "anti-affinity" scheduler policy.

    It's possible to hit a similar race condition for server groups with
    the "affinity" policy. Suppose we create a new group and then create two
    instances simultaneously. The scheduler sees an empty group for each,
    assigns them to different compute nodes, and the policy is violated.

    To guard against this, we extend _validate_instance_group_policy()
    to cover the "affinity" case as well as "anti-affinity".

    Partial-Bug: #1423648
    Change-Id: Icf95390a128e2062293e1f5b7b78fe79747f5f27