Humio uses Kafka for queuing incoming messages and for storing shared state when running Humio in a cluster setup.
It is possible for Humio to snapshot its state. and continue running using a new Kafka cluster. This can be useful in situations where you want to change infrastructure or if there are problems with the current Kafka/Zookeeper cluster. One example could be all Zookeeper machines have written the disk full and afterwards Zookeeper will not start because of file inconsistencies.
This section describes the procedure for doing a Kafka switch.
If it is possible, stop sending data to Humio, then wait for Humio to process all data on the ingest queue.
The ‘Humio stats’ dashboard in the Humio repository has the graphs ‘Events processed after ingest queue by host per second’ and ‘Ingest latency’ that will show this.
If there is data on the ingest queue after closing Humio it will be lost as the queue is reset or another queue will be used.
There are three options for switching Kafka and Zookeeper.
HUMIO_KAFKA_TOPIC_PREFIX to detect the changes.These options are described in more detail below:
Configure Humio to use the new Kafka cluster.
First, delete everything inside Kafka’s data directory.
Then delete the folder version-2 inside Zookeeper’s data directory.
It is important that you not delete the Zookeeper file myid in Zookeeper’s data directory.
myid is a configuration file that contains the id of the Zookeeper node in the Zookeeper cluster and must be there at startup.
Now we have actually created completely new Zookeeper and Kafka clusters.
Instead of resetting Kafka Zookeeper as described above, you can let Humio use a new set of queues in the existing Kafka cluster.
For this to work, Humio must be configured with a new HUMIO_KAFKA_TOPIC_PREFIX.
It is important to note that it will not work to delete and recreate topics with the same names.
In that case Humio cannot detect the Kafka switch.
If Kafka is managed by Humio (KAFKA_MANAGED_BY_HUMIO), the new topics will be created automatically when Humio starts up.
Otherwise you must create topics externally before you start Humio.
Now we are ready to get the Kafka/Zookeper 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 verifying the Kafka cluster.
Now it is time to start the Humio nodes.
It is important to start one Humio node first. This node will detect the Kafka switch and create a new epoc in Humio.
If you are running multiple Humio processes on one Machine (with multiple CPUs), make sure to only start one Humio process.
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=${newEpoch}
When the first node is up and running and the above logline confirms a new epoch has been created, the rest of the Humio nodes can be started.
Now the Humio cluster should be running again. Check the cluster nodes in the admin UI: http://$HUMIOHOST/system/administration/partitions/ingest
In short, to do a Kafka switch follow these steps: