Comment 2 for bug 1268610

Reviewed: https://review.openstack.org/112159
Committed: https://git.openstack.org/cgit/openstack/sahara/commit/?id=4b3910f8c58f4b4d9714c70cadfd4c35040382a9
Submitter: Jenkins
Branch: master

commit 4b3910f8c58f4b4d9714c70cadfd4c35040382a9
Author: Andrew Lazarev <email address hidden>
Date: Mon Aug 25 17:48:20 2014 -0700

    Switched anti-affinity feature to server groups

    Switched implementation of anti affinity to server groups for both
    direct and heat engine.

    Direct engine change is backward compatible. Sahara will detect if
    old logic is used and will use the same logic for cluster scaling.

    Note, behavior of anti-affinity changed. Now Sahara will create one
    server group for cluster and will assign all affected instances to it.
    So, if anti-affinity enabled for datanode (`dn`) and tasktracker (`tt`)
    Sahara will not assign node with `dn` and node with `tt` to the same
    compute.

    Also note, that server group support will be added to heat only in
    juno-3. So, environment with up-to-date heat is required.

    Closes-Bug: #1268610
    Implements: blueprint anti-affinity-via-server-groups
    Change-Id: I501438d84f3a486dad30081b05933f59ebab4858