On reflection I think comments 7 and 8 are correct and it's a juju bug. Looking into it showed that unit hacluster-aodh/1 was missing from the hanode relationship with hacluster-aodh/0 but only from hacluster-aodh/0's point of view. Inspecting the relationship from hacluster-aodh/1's point of view correctly shows both peer nodes (hacluster-aodh/0 and hacluster-aodh/2). juju version: 2.9.33-ubuntu-amd64 $ juju run --application hacluster-aodh "relation-ids hanode" [11/51] - Stdout: | hanode:8 UnitId: hacluster-aodh/1 - Stdout: | hanode:8 UnitId: hacluster-aodh/2 - Stdout: | hanode:8 UnitId: hacluster-aodh/0 $ juju run --application hacluster-aodh "relation-list -r hanode:8" - Stdout: | hacluster-aodh/2 UnitId: hacluster-aodh/0 - Stdout: | hacluster-aodh/0 hacluster-aodh/2 UnitId: hacluster-aodh/1 - Stdout: | hacluster-aodh/0 hacluster-aodh/1 UnitId: hacluster-aodh/2 $ juju status aodh Model Controller Cloud/Region Version SLA Timestamp openstack foundations-maas maas_cloud/default 2.9.33 unsupported 08:46:42Z SAAS Status Store URL grafana active foundations-maas admin/lma-maas.grafana graylog active foundations-maas admin/lma-maas.graylog nagios active foundations-maas admin/lma-maas.nagios prometheus active foundations-maas admin/lma-maas.prometheus App Version Status Scale Charm Channel Rev Exposed Message aodh 14.0.0 active 3 aodh yoga/stable 77 no Unit is ready aodh-mysql-router 8.0.30 active 3 mysql-router 8.0/stable 35 no Unit is ready filebeat 6.8.23 active 3 filebeat candidate 38 no Filebeat ready. hacluster-aodh waiting 3 hacluster edge 109 no Resource: res_aodh_272179f_vip not yet configured logrotated active 3 logrotated candidate 7 no Unit is ready. nrpe active 3 nrpe candidate 94 no Ready prometheus-grok-exporter maintenance 3 prometheus-grok-exporter candidate 8 no Installing software public-policy-routing active 3 advanced-routing candidate 11 no Unit is ready telegraf active 3 telegraf candidate 54 no Monitoring ceph-osd/2 (source version/commit 76901fd) Unit Workload Agent Machine Public address Ports Message aodh/0* active idle 0/lxd/0 10.246.165.92 8042/tcp Unit is ready aodh-mysql-router/0* active idle 10.246.165.92 Unit is ready filebeat/30 active idle 10.246.165.92 Filebeat ready. hacluster-aodh/0* waiting idle 10.246.165.92 Resource: res_aodh_272179f_vip not yet configured logrotated/24 active idle 10.246.165.92 Unit is ready. nrpe/36 active idle 10.246.165.92 icmp,5666/tcp Ready prometheus-grok-exporter/31 active idle 10.246.165.92 9144/tcp Unit is ready public-policy-routing/13 active idle 10.246.165.92 Unit is ready telegraf/29 active idle 10.246.165.92 9103/tcp Monitoring aodh/0 (source version/commit 76901fd) aodh/1 active idle 1/lxd/0 10.246.166.208 8042/tcp Unit is ready aodh-mysql-router/1 active idle 10.246.166.208 Unit is ready filebeat/31 active idle 10.246.166.208 Filebeat ready. hacluster-aodh/1 waiting idle 10.246.166.208 Resource: res_aodh_272179f_vip not yet configured logrotated/25 active idle 10.246.166.208 Unit is ready. nrpe/37 active idle 10.246.166.208 icmp,5666/tcp Ready prometheus-grok-exporter/30 active idle 10.246.166.208 9144/tcp Unit is ready public-policy-routing/14 active idle 10.246.166.208 Unit is ready telegraf/31 active idle 10.246.166.208 9103/tcp Monitoring aodh/1 (source version/commit 76901fd) aodh/2 active idle 2/lxd/0 10.246.165.66 8042/tcp Unit is ready aodh-mysql-router/2 active idle 10.246.165.66 Unit is ready filebeat/64 active idle 10.246.165.66 Filebeat ready. hacluster-aodh/2 waiting idle 10.246.165.66 Resource: res_aodh_272179f_vip not yet configured logrotated/56 active idle 10.246.165.66 Unit is ready. nrpe/68 active idle 10.246.165.66 icmp,5666/tcp Ready prometheus-grok-exporter/62 active idle 10.246.165.66 9144/tcp Unit is ready public-policy-routing/35 active idle 10.246.165.66 Unit is ready telegraf/63 active idle 10.246.165.66 9103/tcp Monitoring aodh/2 (source version/commit 76901fd) Machine State Address Inst id Series AZ Message 0 started 10.246.164.163 solqa-lab1-server-37 jammy zone1 Deployed 0/lxd/0 started 10.246.165.92 juju-30865a-0-lxd-0 jammy zone1 Container started 1 started 10.246.166.192 solqa-lab1-server-32 jammy zone2 Deployed 1/lxd/0 started 10.246.166.208 juju-30865a-1-lxd-0 jammy zone2 Container started 2 started 10.246.165.238 solqa-lab1-server-33 jammy zone3 Deployed 2/lxd/0 started 10.246.165.66 juju-30865a-2-lxd-0 jammy zone3 Container started