Comment 7 for bug 1852759

Reviewed: https://review.opendev.org/699496
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=511b3b0a446694dbd9fc97a4b5a4263b2bfab2fb
Submitter: Zuul
Branch: stable/pike

commit 511b3b0a446694dbd9fc97a4b5a4263b2bfab2fb
Author: Balazs Gibizer <email address hidden>
Date: Fri Nov 15 16:31:04 2019 +0100

    Fix false ERROR message at compute restart

    If an empty compute is restarted a false ERROR message was printed in
    the log as the placement report client does not distinguish between
    error from placement from empty allocation dict from placement.

    This patch changes get_allocations_for_resource_provider to return None
    in case of error instead of an empty dict. This is in line with
    @safe_connect that would make the call return None as well. The
    _error_out_instances_whose_build_was_interrupted also is changed to check
    for None instead of empty dict before reporting the ERROR. The only
    other caller of get_allocations_for_resource_provider was already
    checking for None and converting it to an empty dict so from that caller
    perspective this is compatible change on the report client.

    This is stable only change as get_allocations_for_resource_provider was
    improved during stein[1] to raise on placement error.

    [1]I020e7dc47efc79f8907b7bfb753ec779a8da69a1

    Conflicts:
          nova/compute/manager.py

    NOTE(mriedem): The conflict and changes to test_compute_mgr.py
    are due to not having change I7891b98f225f97ad47f189afb9110ef31c810717
    in Pike which added the context argument to method
    get_allocations_for_resource_provider.

    Change-Id: I6042e493144d4d5a29ec6ab23ffed6b3e7f385fe
    Closes-Bug: #1852759
    (cherry picked from commit 64f797a0514b0276540d4f6c28cb290383088e35)
    (cherry picked from commit 4fcb7816bc88fd513debe70b95aa60bff74e37fb)