traceback due to malformed ceph request when upgrading from ~15.04 to 17.11

Upgrading glance from ~15.04 (r113, revision-id: <email address hidden>) to 17.11 yielded the following traceback:

2018-02-07 22:54:37 INFO config-changed File "/var/lib/juju/agents/unit-glance-0/charm/hooks/config-changed", line 328, in ceph_changed
2018-02-07 22:54:37 INFO config-changed if is_request_complete(get_ceph_request()):
2018-02-07 22:54:37 INFO config-changed File "/var/lib/juju/agents/unit-glance-0/charm/hooks/charmhelpers/contrib/storage/linux/ceph.py", line 1270, in is_request_complete
2018-02-07 22:54:37 INFO config-changed states = get_request_states(request, relation=relation)
2018-02-07 22:54:37 INFO config-changed File "/var/lib/juju/agents/unit-glance-0/charm/hooks/charmhelpers/contrib/storage/linux/ceph.py", line 1231, in get_request_states
2018-02-07 22:54:37 INFO config-changed previous_request = get_previous_request(rid)
2018-02-07 22:54:37 INFO config-changed File "/var/lib/juju/agents/unit-glance-0/charm/hooks/charmhelpers/contrib/storage/linux/ceph.py", line 1211, in get_previous_request
2018-02-07 22:54:37 INFO config-changed request_id=request_data['request-id'])
2018-02-07 22:54:37 INFO config-changed KeyError: 'request-id'

From examining the code it seems that the ~15.04 version of glance has a very early version of the ceph code. Later versions added the request-id field but did not bump api-version, and also apparently cannot cope when it's missing.

The following workaround (adjusted to match the actual request as needed) and juju resolved --retry completed the upgrade.

juju run --unit glance/0 'relation-set -r $(relation-ids ceph) broker_req="{\"api-version\": 1, \"request-id\": \"'$(uuid -v1)'\", \"ops\": [{\"replicas\": 3, \"name\": \"glance\", \"op\": \"create-pool\"}]}"'