10.3. Handling changes to topics

If you are reverting back to a version of Streams for Apache Kafka earlier than 2.8, which uses internal topics for the storage of topic metadata, you still downgrade your Cluster Operator to the previous version, then downgrade Kafka brokers and client applications to the previous Kafka version as standard.

If you are reverting back to a version of Streams for Apache Kafka earlier than 1.7, which uses ZooKeeper for the storage of topic metadata, you still downgrade your Cluster Operator to the previous version, then downgrade Kafka brokers and client applications to the previous Kafka version as standard.

However, you must also delete the topics that were created for the topic store using a kafka-topics command, specifying the bootstrap address of the Kafka cluster. For example:

oc run kafka-admin -ti --image=registry.redhat.io/amq-streams/kafka-38-rhel9:2.8.0 --rm=true --restart=Never -- ./bin/kafka-topics.sh --bootstrap-server localhost:9092 --topic __strimzi-topic-operator-kstreams-topic-store-changelog --delete && ./bin/kafka-topics.sh --bootstrap-server localhost:9092 --topic __strimzi_store_topic --delete

The command must correspond to the type of listener and authentication used to access the Kafka cluster.

The Topic Operator will reconstruct the ZooKeeper topic metadata from the state of the topics in Kafka.

Applications can trigger the automatic creation of topics in the Kafka cluster. By default, the Kafka broker configuration auto.create.topics.enable is set to true, allowing the broker to create topics automatically when an application attempts to produce or consume from a non-existing topic. Applications might also use the Kafka AdminClient to automatically create topics. When an application is deployed along with its KafkaTopic resources, it is possible that automatic topic creation in the cluster happens before the Topic Operator can react to the KafkaTopic.

The topics created for an application deployment are initially created with default topic configuration. If the Topic Operator attempts to reconfigure the topics based on KafkaTopic resource specifications included with the application deployment, the operation might fail because the required change to the configuration is not allowed. For example, if the change means lowering the number of topic partitions. For this reason, it is recommended to disable auto.create.topics.enable in the Kafka cluster configuration.