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 use a new set of queues in the existing Kafka cluster. When reusing the same Kafka cluster, must be configured with a new HUMIO_KAFKA_TOPIC_PREFIX to detect the changes.

To make this process easier, the ALLOW_KAFKA_RESET_UNTIL_TIMESTAMP_MS variable can be used to allow kafka resets until a specific timestamp. This allows a reset of the Kafka configuration, with the default (disabled) setting being enabled when the timestamp is reached. It provides a six hour window for the reset to occur. To use, set the environment variable to a time in the future and then follow the instructions in Switching Kafka to reset the Kafka configuration.

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

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 nodes. It's important to start one node first. This node will detect the Kafka switch and create a new epoch in .

To verify that the Kafka switch was detected and handled, look for this line in the debug log:

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 nodes can be started.

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