Create action to return AZ name

[Alvaro Uria]

In order to script a verification of safe removal of ceph-osd units, a new action would be required.

* Action name: get-availability-zone
- If "customize-failure-domain" config parameter is enabled, use the Juju env var "JUJU_AVAILABILITY_ZONE"
- Otherwise, use “availability_zone” config parameter value (can different ceph-osd applications be part of the same Ceph cluster; because the same application would share the "availability_zone" value, if set)?
- Otherwise, use “per-host” value as default replication per host

[Billy Olsen (billy-olsen)]

Does the safe removal use the `ceph osd safe-to-destroy` command under the hood?

[Billy Olsen (billy-olsen)]

oh, I see - you're referencing the removal of the ceph-osd units, not an osd itself. ignore me

[Robert Gildein (rgildein)]

After a deeper examination of the code, I found that "ceph-osd" uses a CRUSH map with "rack" and "row". The "rack" is set by the environment variable "JUJU_AVAILABILITY_ZONE" and the "row" with the configuration "availability_zone" option. Both of these values are used only if the "customize-failure-domain" value is true. For this reason, I believed that the best approach would be for the "get-availability-zone" action to return the dictionary using the "rack" and "row" keys. If the values for both keys are None, it will represent replication per host.

[Robert Gildein (rgildein)]

review: https://review.opendev.org/c/openstack/charm-ceph-osd/+/778159

[Aurelien Lourot (aurelien-lourot)]

Added charm-guide as affected project so we don't forget about the release notes.

[Robert Gildein (rgildein)]

Thanks, I added the release note. [1]
---
[1]: https://review.opendev.org/c/openstack/charm-guide/+/807170

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/c/openstack/charm-ceph-osd/+/778159
Committed: https://opendev.org/openstack/charm-ceph-osd/commit/d0d3d3edf513f95d4ae0f5c6f58b3c02acd000db
Submitter: "Zuul (22348)"
Branch: master

commit d0d3d3edf513f95d4ae0f5c6f58b3c02acd000db
Author: Robert Gildein <email address hidden>
Date: Tue Mar 2 11:14:37 2021 +0100

    Add an action to provide information about AZ

    The 'get-availability-zone' action will get information about an
    availability zone that will contain information about the CRUSH
    structure. Specifically 'rack' and 'row'.

    Closes-Bug: #1911006
    Change-Id: I99ebbef5f23d6efe3c848b089c7f2b0d26ad0077

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/c/openstack/charm-guide/+/807170
Committed: https://opendev.org/openstack/charm-guide/commit/7dc88337690a5e403b95f1a9d6105099b0967de2
Submitter: "Zuul (22348)"
Branch: master

commit 7dc88337690a5e403b95f1a9d6105099b0967de2
Author: Robert Gildein <email address hidden>
Date: Thu Sep 2 17:30:00 2021 +0200

    ceph-osd charm: new action to display availability zones information

    The ceph-osd charm has a new action: ``get-availability-zone``.

    This action returns availability zone information that contains CRUSH structure
    information. Specifically 'rack', 'row', etc.

    Closes-Bug: #1911006
    Change-Id: Ib9cb089c9c3ea6b2abcf9ba6ca28fa9cf96b6470