hook failed: "update-status" when relating for more than one application

[ashugauttam225]

adding hw-observer for one application worked fine(let say nova-compute), but when adding it for other application in the same model i.e ceph-osd or ubuntu(which are on metal) it is getting failed with the below error.

detailed error log:

unit-hardware-observer-11: 14:22:39 INFO unit.hardware-observer/11.juju-log Writing file to /etc/hardware-exporter-config.yaml.
unit-hardware-observer-11: 14:22:39 INFO unit.hardware-observer/11.juju-log Writing file to /etc/hardware-exporter-config.yaml - Done.
unit-hardware-observer-11: 14:22:39 ERROR unit.hardware-observer/11.juju-log Uncaught exception while in charm code:
Traceback (most recent call last):
File "/var/lib/juju/agents/unit-hardware-observer-11/charm/./src/charm.py", line 173, in
ops.main(HardwareObserverCharm) # type: ignore
File "/var/lib/juju/agents/unit-hardware-observer-11/charm/venv/ops/main.py", line 451, in call
return main(charm_class, use_juju_for_storage=use_juju_for_storage)
File "/var/lib/juju/agents/unit-hardware-observer-11/charm/venv/ops/main.py", line 436, in main
_emit_charm_event(charm, dispatcher.event_name)
File "/var/lib/juju/agents/unit-hardware-observer-11/charm/venv/ops/main.py", line 144, in _emit_charm_event
event_to_emit.emit(*args, **kwargs)
File "/var/lib/juju/agents/unit-hardware-observer-11/charm/venv/ops/framework.py", line 340, in emit
framework._emit(event)
File "/var/lib/juju/agents/unit-hardware-observer-11/charm/venv/ops/framework.py", line 842, in _emit
self._reemit(event_path)
File "/var/lib/juju/agents/unit-hardware-observer-11/charm/venv/ops/framework.py", line 931, in _reemit
custom_handler(event)
File "/var/lib/juju/agents/unit-hardware-observer-11/charm/./src/charm.py", line 144, in _on_config_changed
self._on_update_status(event)
File "/var/lib/juju/agents/unit-hardware-observer-11/charm/./src/charm.py", line 90, in _on_update_status
if not self.model.get_relation("cos-agent"):
File "/var/lib/juju/agents/unit-hardware-observer-11/charm/venv/ops/model.py", line 237, in get_relation
return self.relations._get_unique(relation_name, relation_id)
File "/var/lib/juju/agents/unit-hardware-observer-11/charm/venv/ops/model.py", line 864, in _get_unique
raise TooManyRelatedAppsError(relation_name, num_related, 1)
ops.model.TooManyRelatedAppsError: Too many remote applications on cos-agent (3 > 1)
unit-hardware-observer-11: 14:22:40 ERROR juju.worker.uniter.operation hook "config-changed" (via hook dispatching script: dispatch) failed: exit status 1
unit-hardware-observer-11: 14:22:40 INFO juju.worker.uniter awaiting error resolution for "config-changed" hook
unit-hardware-observer-11: 14:26:18 INFO juju.worker.uniter awaiting error resolution for "config-changed" hook
unit-hardware-observer-11: 14:27:40 INFO juju.worker.uniter awaiting error resolution for "config-changed" hook
unit-hardware-observer-11: 14:27:41 INFO unit.hardware-observer/11.juju-log Setting exporter-log-level to: INFO
unit-hardware-observer-11: 14:27:41 INFO unit.hardware-observer/11.juju-log Setting exporter-port to: 10000
unit-hardware-observer-11: 14:27:41 INFO unit.hardware-observer/11.juju-log Setting redfish-password to:
unit-hardware-observer-11: 14:27:41 INFO unit.hardware-observer/11.juju-log Setting redfish-username to:
unit-hardware-observer-11: 14:27:41 INFO unit.hardware-observer/11.juju-log Detected changes in exporter config.
unit-hardware-observer-11: 14:27:41 INFO unit.hardware-observer/11.juju-log Attempt 1 of /redfish/v1/
unit-hardware-observer-11: 14:27:41 INFO unit.hardware-observer/11.juju-log Response Time for GET to /redfish/v1/: 0.19726872816681862 seconds.
unit-hardware-observer-11: 14:27:42 INFO unit.hardware-observer/11.juju-log Attempt 1 of /redfish/v1/SessionService/Sessions
unit-hardware-observer-11: 14:27:42 INFO unit.hardware-observer/11.juju-log Response Time for POST to /redfish/v1/SessionService/Sessions: 0.1827135756611824 seconds.

[Pjack]

There are 2 grafana-agent and then cause this problem. It may be not a real issue, should remove one of grafana-agent in the environment.

[jneo8]

Adding relation number check in #119