Chapter 18. Upgrading Streams for Apache Kafka and Kafka Upgrade your Kafka cluster with no downtime. Streams for Apache Kafka 2.7 supports and uses Apache Kafka version 3.7.0. Kafka 3.6.0 is supported only for the purpose of upgrading to Streams for Apache Kafka 2.7. You upgrade to the latest supported version of Kafka when you install the latest version of Streams for Apache Kafka. 18.1. Upgrade prerequisites Before you begin the upgrade process, make sure you are familiar with any upgrade changes described in the Streams for Apache Kafka 2.7 on Red Hat Enterprise Linux Release Notes . Note Refer to the documentation supporting a specific version of Streams for Apache Kafka for information on how to upgrade to that version. 18.2. Updating Kafka versions Upgrading Kafka when using ZooKeeper for cluster management requires updates to the Kafka version ( Kafka.spec.kafka.version ) and its inter-broker protocol version ( inter.broker.protocol.version ) in the configuration of the Kafka resource. Each version of Kafka has a compatible version of the inter-broker protocol. The inter-broker protocol is used for inter-broker communication. The minor version of the protocol typically increases to match the minor version of Kafka, as shown in the preceding table. The inter-broker protocol version is set cluster wide in the Kafka resource. To change it, you edit the inter.broker.protocol.version property in Kafka.spec.kafka.config . The following table shows the differences between Kafka versions: Table 18.1. Kafka version differences Streams for Apache Kafka version Kafka version Inter-broker protocol version Log message format version ZooKeeper version 2.7 3.7.0 3.7 3.7 3.8.3 2.6 3.6.0 3.6 3.6 3.8.3 Kafka 3.7.0 is supported for production use. Kafka 3.6.0 is supported only for the purpose of upgrading to Streams for Apache Kafka 2.7. Log message format version When a producer sends a message to a Kafka broker, the message is encoded using a specific format. The format can change between Kafka releases, so messages specify which version of the message format they were encoded with. The properties used to set a specific message format version are as follows: message.format.version property for topics log.message.format.version property for Kafka brokers From Kafka 3.0.0, the message format version values are assumed to match the inter.broker.protocol.version and don't need to be set. The values reflect the Kafka version used. When upgrading to Kafka 3.0.0 or higher, you can remove these settings when you update the inter.broker.protocol.version . Otherwise, you can set the message format version based on the Kafka version you are upgrading to. The default value of message.format.version for a topic is defined by the log.message.format.version that is set on the Kafka broker. You can manually set the message.format.version of a topic by modifying its topic configuration. Rolling updates from Kafka version changes The Cluster Operator initiates rolling updates to Kafka brokers when the Kafka version is updated. Further rolling updates depend on the configuration for inter.broker.protocol.version and log.message.format.version . If Kafka.spec.kafka.config contains... The Cluster Operator initiates... Both the inter.broker.protocol.version and the log.message.format.version . A single rolling update. After the update, the inter.broker.protocol.version must be updated manually, followed by log.message.format.version . Changing each will trigger a further rolling update. Either the inter.broker.protocol.version or the log.message.format.version . Two rolling updates. No configuration for the inter.broker.protocol.version or the log.message.format.version . Two rolling updates. Important From Kafka 3.0.0, when the inter.broker.protocol.version is set to 3.0 or higher, the log.message.format.version option is ignored and doesn't need to be set. The log.message.format.version property for brokers and the message.format.version property for topics are deprecated and will be removed in a future release of Kafka. As part of the Kafka upgrade, the Cluster Operator initiates rolling updates for ZooKeeper. A single rolling update occurs even if the ZooKeeper version is unchanged. Additional rolling updates occur if the new version of Kafka requires a new ZooKeeper version. 18.3. Strategies for upgrading clients Upgrading Kafka clients ensures that they benefit from the features, fixes, and improvements that are introduced in new versions of Kafka. Upgraded clients maintain compatibility with other upgraded Kafka components. The performance and stability of the clients might also be improved. Consider the best approach for upgrading Kafka clients and brokers to ensure a smooth transition. The chosen upgrade strategy depends on whether you are upgrading brokers or clients first. Since Kafka 3.0, you can upgrade brokers and client independently and in any order. The decision to upgrade clients or brokers first depends on several factors, such as the number of applications that need to be upgraded and how much downtime is tolerable. If you upgrade clients before brokers, some new features may not work as they are not yet supported by brokers. However, brokers can handle producers and consumers running with different versions and supporting different log message versions. 18.4. Upgrading Kafka brokers and ZooKeeper Upgrade Kafka brokers and ZooKeeper on a host machine to use the latest version of Streams for Apache Kafka. You update the installation files, then configure and restart all Kafka brokers to use a new inter-broker protocol version. After performing these steps, data is transmitted between the Kafka brokers using the new inter-broker protocol version. Note From Kafka 3.0.0, message format version values are assumed to match the inter.broker.protocol.version and don't need to be set. The values reflect the Kafka version used. Prerequisites You are logged in to Red Hat Enterprise Linux as the kafka user. You have installed Kafka and other Kafka components you are using on separate hosts. For more information, see Section 3.1, "Installation environment" . You have downloaded the installation files . Procedure For each Kafka broker in your Streams for Apache Kafka cluster and one at a time: Download the Streams for Apache Kafka archive from the Streams for Apache Kafka software downloads page . Note If prompted, log in to your Red Hat account. On the command line, create a temporary directory and extract the contents of the amq-streams-<version>-bin.zip file. mkdir /tmp/kafka unzip amq-streams-<version>-bin.zip -d /tmp/kafka If running, stop ZooKeeper and the Kafka broker running on the host. /opt/kafka/bin/zookeeper-server-stop.sh /opt/kafka/bin/kafka-server-stop.sh jcmd | grep zookeeper jcmd | grep kafka If you are running Kafka on a multi-node cluster, see Section 4.3, "Performing a graceful rolling restart of Kafka brokers" . Delete the libs and bin directories from your existing installation: rm -rf /opt/kafka/libs /opt/kafka/bin Copy the libs and bin directories from the temporary directory: cp -r /tmp/kafka/kafka_<version>/libs /opt/kafka/ cp -r /tmp/kafka/kafka_<version>/bin /opt/kafka/ If required, update the configuration files in the config directory to reflect any changes in the new versions. Delete the temporary directory. rm -r /tmp/kafka Edit the /opt/kafka/config/server.properties properties file. Set the inter.broker.protocol.version and log.message.format.version properties to the current version. For example, the current version is 3.6 if upgrading from Kafka version 3.6.0 to 3.7.0: inter.broker.protocol.version=3.6 log.message.format.version=3.6 Use the correct version for the Kafka version you are upgrading from ( 3.5 , 3.6 , and so on). Leaving the inter.broker.protocol.version unchanged at the current setting ensures that the brokers can continue to communicate with each other throughout the upgrade. If the properties are not configured, add them with the current version. If you are upgrading from Kafka 3.0.0 or later, you only need to set the inter.broker.protocol.version . Restart the updated ZooKeeper and Kafka broker: /opt/kafka/bin/zookeeper-server-start.sh -daemon /opt/kafka/config/zookeeper.properties /opt/kafka/bin/kafka-server-start.sh -daemon /opt/kafka/config/server.properties The Kafka broker and ZooKeeper start using the binaries for the latest Kafka version. For information on restarting brokers in a multi-node cluster, see Section 4.3, "Performing a graceful rolling restart of Kafka brokers" . Verify that the restarted Kafka broker has caught up with the partition replicas it is following. Use the kafka-topics.sh tool to ensure that all replicas contained in the broker are back in sync. For instructions, see Listing and describing topics . In the steps, update your Kafka brokers to use the new inter-broker protocol version. Update each broker, one at a time. Warning Downgrading Streams for Apache Kafka is not possible after completing the following steps. Set the inter.broker.protocol.version property to 3.7 in the /opt/kafka/config/server.properties file: inter.broker.protocol.version=3.7 On the command line, stop the Kafka broker that you modified: /opt/kafka/bin/kafka-server-stop.sh Check that Kafka is not running: jcmd | grep kafka Restart the Kafka broker that you modified: /opt/kafka/bin/kafka-server-start.sh -daemon /opt/kafka/config/server.properties Check that Kafka is running: jcmd | grep kafka If you are upgrading from a version earlier than Kafka 3.0.0, set the log.message.format.version property to 3.7 in the /opt/kafka/config/server.properties file: log.message.format.version=3.7 On the command line, stop the Kafka broker that you modified: /opt/kafka/bin/kafka-server-stop.sh Check that Kafka is not running: jcmd | grep kafka Restart the Kafka broker that you modified: /opt/kafka/bin/kafka-server-start.sh -daemon /opt/kafka/config/server.properties Check that Kafka is running: jcmd | grep kafka Verify that the restarted Kafka broker has caught up with the partition replicas it is following. Use the kafka-topics.sh tool to ensure that all replicas contained in the broker are back in sync. For instructions, see Listing and describing topics . If it was used in the upgrade, remove the legacy log.message.format.version configuration from the server.properties file. Upgrading client applications Ensure all Kafka client applications are updated to use the new version of the client binaries as part of the upgrade process and verify their compatibility with the Kafka upgrade. If needed, coordinate with the team responsible for managing the client applications. Tip To check that a client is using the latest message format, use the kafka.server:type=BrokerTopicMetrics,name={Produce|Fetch}MessageConversionsPerSec metric. The metric shows 0 if the latest message format is being used. 18.5. Upgrading Kafka components Upgrade Kafka components on a host machine to use the latest version of Streams for Apache Kafka. You can use the Streams for Apache Kafka installation files to upgrade the following components: Kafka Connect MirrorMaker Kafka Bridge (separate ZIP file) Prerequisites You are logged in to Red Hat Enterprise Linux as the kafka user. You have downloaded the installation files . You have upgraded Kafka . If a Kafka component is running on the same host as Kafka, you'll also need to stop and start Kafka when upgrading. Procedure For each host running an instance of the Kafka component: Download the Streams for Apache Kafka or Kafka Bridge installation files from the Streams for Apache Kafka software downloads page . Note If prompted, log in to your Red Hat account. On the command line, create a temporary directory and extract the contents of the amq-streams-<version>-bin.zip file. mkdir /tmp/kafka unzip amq-streams-<version>-bin.zip -d /tmp/kafka For Kafka Bridge, extract the amq-streams-<version>-bridge-bin.zip file. If running, stop the Kafka component running on the host. Delete the libs and bin directories from your existing installation: rm -rf /opt/kafka/libs /opt/kafka/bin Copy the libs and bin directories from the temporary directory: cp -r /tmp/kafka/kafka_<version>/libs /opt/kafka/ cp -r /tmp/kafka/kafka_<version>/bin /opt/kafka/ If required, update the configuration files in the config directory to reflect any changes in the new versions. Delete the temporary directory. rm -r /tmp/kafka Start the Kafka component using the appropriate script and properties files. Starting Kafka Connect in standalone mode /opt/kafka/bin/connect-standalone.sh \ /opt/kafka/config/connect-standalone.properties <connector1> .properties [ <connector2> .properties ...] Starting Kafka Connect in distributed mode /opt/kafka/bin/connect-distributed.sh \ /opt/kafka/config/connect-distributed.properties Starting MirrorMaker 2 in dedicated mode /opt/kafka/bin/connect-mirror-maker.sh \ /opt/kafka/config/connect-mirror-maker.properties Starting Kafka Bridge su - kafka ./bin/kafka_bridge_run.sh \ --config-file= <path> /application.properties Verify that the Kafka component is running, and producing or consuming data as expected. Verifying Kafka Connect in standalone mode is running jcmd | grep ConnectStandalone Verifying Kafka Connect in distributed mode is running jcmd | grep ConnectDistributed Verifying MirrorMaker 2 in dedicated mode is running jcmd | grep mirrorMaker Verifying Kafka Bridge is running by checking the log HTTP-Kafka Bridge started and listening on port 8080 HTTP-Kafka Bridge bootstrap servers localhost:9092

Commands:
mkdir /tmp/kafka unzip amq-streams-<version>-bin.zip -d /tmp/kafka
/opt/kafka/bin/zookeeper-server-stop.sh /opt/kafka/bin/kafka-server-stop.sh jcmd | grep zookeeper jcmd | grep kafka
rm -rf /opt/kafka/libs /opt/kafka/bin
cp -r /tmp/kafka/kafka_<version>/libs /opt/kafka/ cp -r /tmp/kafka/kafka_<version>/bin /opt/kafka/
rm -r /tmp/kafka
inter.broker.protocol.version=3.6 log.message.format.version=3.6
/opt/kafka/bin/zookeeper-server-start.sh -daemon /opt/kafka/config/zookeeper.properties /opt/kafka/bin/kafka-server-start.sh -daemon /opt/kafka/config/server.properties
inter.broker.protocol.version=3.7
/opt/kafka/bin/kafka-server-stop.sh
jcmd | grep kafka
/opt/kafka/bin/kafka-server-start.sh -daemon /opt/kafka/config/server.properties
jcmd | grep kafka
log.message.format.version=3.7
/opt/kafka/bin/kafka-server-stop.sh
jcmd | grep kafka
/opt/kafka/bin/kafka-server-start.sh -daemon /opt/kafka/config/server.properties
jcmd | grep kafka
mkdir /tmp/kafka unzip amq-streams-<version>-bin.zip -d /tmp/kafka
rm -rf /opt/kafka/libs /opt/kafka/bin
cp -r /tmp/kafka/kafka_<version>/libs /opt/kafka/ cp -r /tmp/kafka/kafka_<version>/bin /opt/kafka/
rm -r /tmp/kafka
/opt/kafka/bin/connect-standalone.sh /opt/kafka/config/connect-standalone.properties <connector1> .properties [ <connector2> .properties ...]
/opt/kafka/bin/connect-distributed.sh /opt/kafka/config/connect-distributed.properties
/opt/kafka/bin/connect-mirror-maker.sh /opt/kafka/config/connect-mirror-maker.properties
su - kafka ./bin/kafka_bridge_run.sh --config-file= <path> /application.properties
jcmd | grep ConnectStandalone
jcmd | grep ConnectDistributed
jcmd | grep mirrorMaker
HTTP-Kafka Bridge started and listening on port 8080 HTTP-Kafka Bridge bootstrap servers localhost:9092