Comment 6 for bug 2071939

I built a ceilometer Rock from the UCA caracal-proposed and was able to confirm this fixes the issue.

Built the rock by applying the following diff to https://github.com/canonical/ubuntu-openstack-rocks/blob/6707266619e67abe4e1a48ab0fe91e81b6aa5b36/rocks/ceilometer-consolidated/rockcraft.yaml#L13

diff --git a/rocks/ceilometer-consolidated/rockcraft.yaml b/rocks/ceilometer-consolidated/rockcraft.yaml
index e9679b1..bcc49b5 100644
--- a/rocks/ceilometer-consolidated/rockcraft.yaml
+++ b/rocks/ceilometer-consolidated/rockcraft.yaml
@@ -13,6 +13,7 @@ platforms:
 package-repositories:
   - type: apt
     cloud: caracal
+ pocket: proposed
     priority: always

From inside the Rock
apt policy ceilometer-agent-notification
ceilometer-agent-notification:
  Installed: 2:22.0.0-0ubuntu1.1~cloud0
  Candidate: 2:22.0.0-0ubuntu1.1~cloud0
  Version table:
 *** 2:22.0.0-0ubuntu1.1~cloud0 100
        100 /var/lib/dpkg/status

I can confirm the notification agent is now starting with the following logs

2024-07-15 17:23:28
2024-07-15 15:23:27.065 22 WARNING ceilometer.publisher.gnocchi [-] Filtered project [service] not found in keystone, ignoring the filter_project option: keystoneauth1.exceptions.http.NotFound: 404 (HTTP 404)

2024-07-15 17:23:26
2024-07-15 15:23:25.925 22 WARNING ceilometer.pipeline.sample [-] metering data image.size for 983818c1-1c70-488d-9a7f-02ac94f43aa1 @ 2024-07-11T15:33:30.023650+00:00 has no volume (volume: None), the sample will be dropped

2024-07-15 17:23:26
2024-07-15 15:23:25.915 22 WARNING ceilometer.pipeline.sample [-] metering data image.size for cbcc29a7-adb7-4272-a4b6-ac577c06e9fe @ 2024-07-11T15:32:49.683748+00:00 has no volume (volume: None), the sample will be dropped

2024-07-15 17:23:26
2024-07-15 15:23:25.897 22 WARNING ceilometer.pipeline.sample [-] metering data image.size for 841ec872-05e2-4347-999d-26420e5a8194 @ 2024-07-11T15:32:10.519858+00:00 has no volume (volume: None), the sample will be dropped

2024-07-15 17:23:26
2024-07-15 15:23:25.887 22 WARNING oslo.messaging._drivers.pool [-] Connection pool limit exceeded: current size 30 surpasses max configured rpc_conn_pool_size 30

/* removed duplicated spam logs */

2024-07-15 17:23:26
2024-07-15 15:23:25.683 22 WARNING oslo.messaging._drivers.pool [-] Connection pool limit exceeded: current size 30 surpasses max configured rpc_conn_pool_size 30

2024-07-15 17:23:26
Sub('sub(/.*/, )')

2024-07-15 17:23:21
2024-07-15 15:23:15.781 22 INFO ceilometer.publisher.messaging [-] Publishing policy set to default

2024-07-15 17:23:20
2024-07-15 15:23:15.781 22 INFO ceilometer.publisher.messaging [-] Publishing policy set to default

Before the fix, the notification didn't start, failing on the reported exception.