nova-manage placement heal allocation command wrongly assumes allocation not exists for an instance if placement returns error code

[Balazs Gibizer]

The nova-manage placement heal_allocation implementation queries the instance consumer from placement[1][2]. It assumes that if the placement query returned a non 200 response then the consumer does not exists and needs to be healed. However placement returns http 200 even if the consumer does not exits [3] so the assumption in [1] is invalid.

[1]https://github.com/openstack/nova/blob/de2c04981b438d4d10d4ee0207d79b4d3ec5135e/nova/cmd/manage.py#L1718-L1727
[2]https://github.com/openstack/nova/blob/de2c04981b438d4d10d4ee0207d79b4d3ec5135e/nova/scheduler/client/report.py#L1509
[3] https://developer.openstack.org/api-ref/placement/?expanded=list-allocations-detail#list-allocations

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/669188

[Chris Dent (cdent)]

To clarify the issue here (I think most people reading this will already know but just for clarify), this is common behavior for "collection" style HTTP API responses. If the response is a list, a list with 0 members is a 200 response.

So as long as the identifier passed to GET /allocation/{identifier} is well-formed, you'll get back a list, because that identifier notionally identifies a group of allocations that may exist, but right now is empty.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/669188
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=e6f011926295e0a36fa06c46f69525bcd7fa25dd
Submitter: Zuul
Branch: master

commit e6f011926295e0a36fa06c46f69525bcd7fa25dd
Author: Balazs Gibizer <email address hidden>
Date: Thu Jul 4 16:15:33 2019 +0200

    Remove assumption of http error if consumer not exists

    The heal_allocations_for_instance assumes that placement GET
    /allocations/<instance_uuid> query returns an error code if the consumer
    does not exists in placement. However placement returns an empty
    allocation instead.

    This patch removes such assumption and treates the negative response
    from placement as a fatal error.

    Change-Id: I7e2df32029e4cff57a0dddcd905b6c1aac207546
    Closes-Bug: #1835419

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/nova 20.0.0.0rc1 release candidate.