Jeroen, MirrorClient will correctly translate offsets for both failover and failback, exactly as you describe. It's possible to automate failover and failback using that logic. The integration tests automatically fail over and fail back, for example. I've seen it done two ways: during startup within the consumer itself, or in an external tool which writes offsets directly. In either case MirrorClient will give you the correct offsets to resume from.
MirrorCheckpointConnector will automatically write offsets, but only under certain conditions, to avoid accidentally overwriting offsets. I'm not sure whether you can failover and failback using just the automatic behavior. My guess is it works, but you are tripping over one of the safety checks. You might try deleting the consumer group on the source cluster prior to failback. Ryanne On Mon, Jan 8, 2024, 9:10 AM Jeroen Schutrup <jer...@cloudflare.com.invalid> wrote: > Hi all, > I'm exploring using the MirrorSourceConnector and MirrorCheckpointConnector > on Kafka Connect to setup active/active replication between two Kafka > clusters. Using the DefaultReplicationPolicy replication policy class, > messages originating from the source cluster get replicated as expected to > the cluster-prefixed topic in the target cluster. Consumergroup offsets > from the source to target cluster are replicated likewise. However, once > the consumer group migrates from the source to the target cluster, its > offsets are not replicated from the target back to the source cluster. > For an active/active setup I'd want consumer group offsets for topic > <source-cluster-alias>.<topic-name> in the target cluster to be replicated > back to <topic-name> in the source cluster. This would allow consumers to > failover & failback between clusters with minimal duplicate message > consumption. > > To clarify my setup a bit; I'm running two single-broker Kafka clusters in > Docker (cluster A & B), along with a single Connect instance on which I've > provisioned four source connectors: > - A MirrorSourceConnector replicating topics from cluster A to cluster B > - A MirrorSourceConnector replicating topics from cluster B to cluster A > - A MirrorCheckpointConnector translating & replicating offsets from > cluster A to cluster B > - A MirrorCheckpointConnector translating & replicating offsets from > cluster B to cluster A > > I'm not sure whether this is by design, or maybe I'm missing something. > I've seen a similar question posted to KAFKA-9076 [1] without a resolution. > > Regards, > Jeroen > > [1] > > https://issues.apache.org/jira/browse/KAFKA-9076?focusedCommentId=17268908&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#comment-17268908 >
