Debugging failed connectivity between Aiven for Apache MirrorMaker and an external Kafka configured using an integration endpoint is very difficult today. No errors are surfaced in the integration endpoint configuration screen itself, we must wait for the replication flow to attempt to start and then dig out cryptic errors from MM2 logs.

Some kinds of errors (e.g. failure to build SSL keystores) are not even surfaced in MM2 logs and are only visible to Aiven operators.

Please consider adding a basic connectivity check to allow for quicker troubleshooting and iteration. This check should ensure that the network path between Aiven and the external Kafka is correct and the chosen authentication method and credentials are valid.