Recovery

Pre-requisites

Make sure both Rome and Lisbon clusters are deployed following the async deployment guide.

Recover detached cluster

If the relation between clusters was removed and one side went into detached/blocked state: simply relate async replication back to restore ClusterSet.

Recover lost cluster

If a cluster has been lost and the ClusterSet need new member: deploy new db application and init async replication. The data will be copied automatically and the new cluster will join ClusterSet.

Recover invalidated cluster

A cluster in the cluster-set gets invalidated when async replication auto-recovery fails on a disconnection event or when a failover is run against another cluster-set member while this cluster is unreachable.

If the invalidated cluster connections is restored, it’s status will be displayed in juju status as:

App  Version                  Status  Scale  Charm      Channel   Rev  Address         Exposed  Message
db2  8.0.36-0ubuntu0.22.04.1  active      3  mysql-k8s  8.0/edge  137  10.152.183.241  no

Unit    Workload  Agent  Address       Ports  Message
db2/0   active    idle   10.1.124.208      
db2/1*  active    idle   10.1.124.203         Primary (standby, invalidated)
db2/2   active    idle   10.1.124.200      

Which indicates that connectivity is possible, but replication channel is stopped.

To restore the replication operation, run:

juju run db2/leader rejoin-cluster cluster-name=rome

Where rome is the name of the invalidated cluster.