Comment 11 for bug 1454873

Reviewed: https://review.openstack.org/183723
Committed: https://git.openstack.org/cgit/openstack/heat/commit/?id=a5297fec8a470d2aef8e41c1c4bee16f986aff74
Submitter: Jenkins
Branch: stable/kilo

commit a5297fec8a470d2aef8e41c1c4bee16f986aff74
Author: Zane Bitter <email address hidden>
Date: Wed May 13 18:56:32 2015 -0400

    Get rid of circular references in Resource and Function

    Circular references cause practically every bit of data that Heat uses to
    remain in memory until the completion of an operation, and even then to
    only be freed once the loop is detected by the garbage collector. By
    breaking all of the loops using weak references, we can ensure that things
    will get freed when they are no longer referenced without the need to wait
    for garbage collection (which should also take a lot less time). This
    change removes the loops from Resource and Function objects back to the
    Stack.

    Change-Id: Ibf80e95e69a2f27ed29754a2e0f1125e8eed0775
    Closes-Bug: #1454873
    (cherry-picked from commits 2032548c4e501ebf90604bf60a69fdf9f64b981d,
                                203b8e8ecf91ad7c75dd7072c85930de4f8c1c42,
                                d29bb1927489d5590f17d2f3ef2904b6f5edd0d4,
                                60300b014952f5b2fa4c2a9010876f5b871f0f66)