Comment 28 for bug 1731349

Reviewed: https://review.openstack.org/531929
Committed: https://git.openstack.org/cgit/openstack/heat/commit/?id=ac87bc7c7932b9a0245d12a9a46b6fbad42be9b5
Submitter: Zuul
Branch: master

commit ac87bc7c7932b9a0245d12a9a46b6fbad42be9b5
Author: Zane Bitter <email address hidden>
Date: Mon Jan 8 17:23:12 2018 -0500

    Get ResourceGroup/Chain attributes from nested stack outputs

    Since Pike we've generated the templates for various nested stack resource
    types with outputs that produce the attribute values that are referenced in
    the parent stack, and a previous patch did the same for resource IDs. Use
    these output values when available to calculate the attribute values. This
    is efficient, because the all of the outputs are fetched together and
    cached, and avoids using the grouputils functions that cause the nested
    stack to get loaded into memory in the same process.

    Fall back to the existing implementation (using grouputils) if the required
    output isn't available (generally this would be due to the nested stack
    being created on an earlier version of Heat that did not include the
    outputs in the generated template, and not updated since).

    Change-Id: I9146e1d99f494213daef7d61ae75c92a4ef981a9
    Partial-Bug: #1731349