Relation removal prevents normal operations

[Peter Matulis]

After having successfully used ceph-proxy for providing Ceph-backed Glance volumes and Ceph-backed Nova disks I decided to remove the Glance portion so as to use local Glance storage. I discovered that I could not do so. A remnant of the connection to the Ceph cluster appears to have been left behind after the removal of the relation.

The removed relation:

juju remove-relation ceph-proxy:client glance:ceph

The post-removal `juju status` output:

See attachment 'juju-status-post-removal.txt'

The Glance error:

See attachment 'post-ceph-proxy-relation-removal.txt'

I eventually removed the ceph-proxy application but it didn't help. The full `juju status` output in the status attachment was made after ceph-proxy removal.

[James Page (james-page)]

The issue is that the glance charm does not restart it services when the relation to ceph-* is broken:

@hooks.hook('ceph-relation-broken')
def ceph_broken():
    service = service_name()
    delete_keyring(service=service)
    CONFIGS.write_all()

as a result glance is still trying to use ceph but the keyring and ceph.conf are missing/incomplete on disk.

Adding:

@restart_on_change(restart_map())

as a decorator for the function should resolve this.

[James Page (james-page)]

https://review.opendev.org/#/c/742838

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/742838
Committed: https://git.openstack.org/cgit/openstack/charm-glance/commit/?id=78e7b57854fc1d9a1ddefd55f4c92e62b718ad63
Submitter: Zuul
Branch: master

commit 78e7b57854fc1d9a1ddefd55f4c92e62b718ad63
Author: James Page <email address hidden>
Date: Fri Jul 24 10:52:17 2020 +0100

    Fix misc issues with removal of ceph relation

    Ensure that services are restarted when the relation is
    removed from a model.

    Add -departed hook to ensure that ceph.conf is consistent
    with monitors in the ceph cluster during scaleback operations.

    Change-Id: I2159dd32a49e4591494881bab8469f087a539d5a
    Closes-Bug: 1888768