[ironic] list_instances/list_instance_uuid does not respect conductor_group/partition_key

[Jay Faulkner]

The methods on the Ironic driver, list_instances and list_instance_uuids are not currently respecting the conductor_group option: https://opendev.org/openstack/nova/src/branch/master/nova/conf/ironic.py#L71.

This leads to significant performance degradation, as querying Ironic for all nodes (/v1/nodes) instead of all nodes managed by the compute (/v1/nodes?conductor_group=blah) is a significantly more expensive API call.

In addition, this can lead to unexpected behavior for operators, such as an action being taken by a compute serving conductor group "A" to resolve an issue that would normally be resolved by a compute service conductor group "B".

While troubleshooting this error, we dug deeply into what this data is used for; it's used for two things:
- Reconciling deleted instances as a periodic job
- Ensuring no instances exist on a newly-started compute host

These are tasks which either could use stale data or would not be impacted by using the Ironic driver's existing node cache. Therefore, a suggested fix is:

Revise list_instances and list_instance_uuids to reuse the node cache to reduce the overall API calls being made to Ironic, and ensure all /v1/nodes calls use the same codepath in the Ironic driver. It's the belief of JayF, TheJulia, and Johnthetubaguy (on a video call right now) that using stale data, without refreshing the cache, should be safe for these use cases. (Even if we decide to refresh the cache, we should use this code path anyway.)

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/c/openstack/nova/+/900831

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/c/openstack/nova/+/900831
Committed: https://opendev.org/openstack/nova/commit/fa3cf7d50cba921ea67eb161e6a199067ea62deb
Submitter: "Zuul (22348)"
Branch: master

commit fa3cf7d50cba921ea67eb161e6a199067ea62deb
Author: Jay Faulkner <email address hidden>
Date: Mon Nov 13 15:21:31 2023 -0800

    [ironic] Partition & use cache for list_instance*

    list_instances and list_instance_uuids, as written in the Ironic driver,
    do not currently respect conductor_group paritioning. Given a nova
    compute is intended to limit it's scope of work to the conductor group
    it is configured to work with; this is a bug.

    Additionally, this should be a significant performance boost for a
    couple of reasons; firstly, instead of calling the Ironic API and
    getting all nodes, instead of the subset (when using conductor group),
    we're now properly getting the subset of nodes -- this is the optimized
    path in the Ironic DB and API code. Secondly, we're now using the
    driver's node cache to respond to these requests. Since list_instances
    and list_instance_uuids is used by periodic tasks, these operating with
    data that may be slightly stale should have minimal impact compared to
    the performance benefits.

    Closes-bug: #2043036
    Change-Id: If31158e3269e5e06848c29294fdaa147beedb5a5

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/2023.2
Review: https://review.opendev.org/c/openstack/nova/+/906155

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/nova 29.0.0.0rc1 release candidate.