You could reset the current Kafka and ZooKeeper cluster by deleting their data directories on the filesystem on each node. This is the same as starting up a new and empty Kafka/ZooKeeper cluster. To do this, delete everything inside Kafka's data directory. Then delete the folder version-2 inside ZooKeeper's data directory.

It's important that you not delete the ZooKeeper file myid in ZooKeeper's data directory. The myid is a configuration file that contains the id of the ZooKeeper node in the ZooKeeper cluster and must be there at startup.

After doing this, you will have created completely new ZooKeeper and Kafka clusters.

Instead of resetting Kafka as described above, you can let LogScale use a new set of queues in the existing Kafka cluster. When reusing the same Kafka cluster, LogScale must be configured with a new HUMIO_KAFKA_TOPIC_PREFIX to detect the changes.

It's important to note that it will not work to delete and recreate topics with the same names. In that case LogScale cannot detect the Kafka switch. If Kafka is managed by LogScale (KAFKA_MANAGED_BY_HUMIO), the new topics will be created automatically when LogScale starts up. Otherwise you must create topics externally before you start LogScale.

Now you're ready to get the Kafka/ZooKeeper cluster started. This is typically done by starting the ZooKeeper nodes. Wait for all nodes to be running and verify the ZooKeeper cluster. Then start all Kafka nodes, wait for them to be running and verify the Kafka cluster.

Once Kafka and ZooKeeper have started, start the LogScale nodes. It's important to start one LogScale node first. This node will detect the Kafka switch and create a new epoch in LogScale.

To verify that the Kafka switch was detected and handled, look for this logline:

Switching epoch to=${epochKey} from=${latestEpoch.kafkaClusterId}
- I'm the first cluster member to get here
  for this kafka. newEpoch=${newEpoch}

When the first node is up and running and the above logline confirms a new epoch has been created, the rest of the LogScale nodes can be started.

At that point, the LogScale cluster should be running again. Check the cluster nodes in the administrative section of the LogScale user interface: http://$HUMIOHOST/system/administration/partitions/ingest