kafka/docs/zk2kraft.html

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<div class="p-zk2kraft">
    <h4 class="anchor-heading">Significant Changes in Kafka 4.0 Release</h4>
    <p>The following are some of the updates in Kafka 4.0 release:</p>
    <h5 class="anchor-heading">Removal Zookeeper configs</h5>
    <ul>
        <li>
            <p>
                The password encoder-related configurations have been removed. These configurations were used in
                ZooKeeper mode to define the key and backup key for encrypting sensitive data (e.g., passwords), 
                specify the algorithm and key generation method for password encryption (e.g., AES, RSA), and control 
                the key length and encryption strength.
            </p>
            <ul>
                <li><code>password.encoder.secret</code></li>
                <li><code>password.encoder.old.secret</code></li>
                <li><code>password.encoder.keyfactory.algorithm</code></li>
                <li><code>password.encoder.cipher.algorithm</code></li>
                <li><code>password.encoder.key.length</code></li>
                <li><code>password.encoder.iterations</code></li>
            </ul>
            <p>
                In Kraft mode, Kafka stores sensitive data in records, and the data is not encrypted in Kafka.
            </p>
        </li>
        <li>
            <p>
                Removed <code>control.plane.listener.name</code>. Kafka relies on ZooKeeper to manage metadata, but some
                internal operations (e.g., communication between controllers (a.k.a., broker controller) and brokers)
                still require Kafka’s internal control plane for coordination.
            </p>
            <p>
                In KRaft mode, Kafka eliminates its dependency on ZooKeeper, and the control plane functionality is
                fully integrated into Kafka itself. The process roles are clearly separated: brokers handle data-related
                requests, while the controllers (a.k.a., quorum controller) manages metadata-related requests. The controllers 
                use the Raft protocol for internal communication, which operates differently from the ZooKeeper model. Use the
                following parameters to configure the control plane listener:
            </p>
            <ul>
                <li><code>controller.listener.names</code></li>
                <li><code>listeners</code></li>
                <li><code>listener.security.protocol.map</code></li>
            </ul>
        </li>
        <li>
            <p>
                Removed graceful broker shutdowns-related configurations. These configurations were used in ZooKeeper mode
                to define the maximum number of retries and the retry backoff time for controlled shutdowns. It can
                reduce the risk of unplanned leader changes and data inconsistencies.
            </p>
            <ul>
                <li><code>controlled.shutdown.max.retries</code></li>
                <li><code>controlled.shutdown.retry.backoff.ms</code></li>
            </ul>
            <p>
                In KRaft mode, Kafka uses the Raft protocol to manage metadata. The broker shutdown process differs from
                ZooKeeper mode as it is managed by the quorum-based controller. The shutdown process is more reliable
                and efficient due to automated leader transfers and metadata updates handled by the controller.
            </p>
        </li>
        <li>
            <p>
                Remove the broker id generation-related configurations. These configurations were used in ZooKeeper mode
                to define the broker id, specify the broker id auto generation, and control the broker id generation process.
            </p>
            <ul>
                <li><code>reserved.broker.max.id</code></li>
                <li><code>broker.id.generation.enable</code></li>
                <li><code>broker.id</code></li>
            </ul>
            <p>
                Kafka use the node id in Kraft mode to identify servers.
            </p>
            <ul>
                <li><code>node.id</code></li>
            </ul>
        </li>
        <li>
            <p>
                Removed dynamic configurations which relies on ZooKeeper. In KRaft mode, to change these configurations,
                you need to restart the broker/controller.
            </p>
            <ul>
                <li><code>advertised.listeners</code></li>
            </ul>
        </li>
        <li>
            <p>
                Removed Zookeeper related configurations.
            </p>
            <ul>
                <li><code>zookeeper.connect</code></li>
                <li><code>zookeeper.session.timeout.ms</code></li>
                <li><code>zookeeper.connection.timeout.ms</code></li>
                <li><code>zookeeper.set.acl</code></li>
                <li><code>zookeeper.max.in.flight.requests</code></li>
                <li><code>zookeeper.ssl.client.enable</code></li>
                <li><code>zookeeper.clientCnxnSocket</code></li>
                <li><code>zookeeper.ssl.keystore.location</code></li>
                <li><code>zookeeper.ssl.keystore.password</code></li>
                <li><code>zookeeper.ssl.keystore.type</code></li>
                <li><code>zookeeper.ssl.truststore.location</code></li>
                <li><code>zookeeper.ssl.truststore.password</code></li>
                <li><code>zookeeper.ssl.truststore.type</code></li>
                <li><code>zookeeper.ssl.protocol</code></li>
                <li><code>zookeeper.ssl.enabled.protocols</code></li>
                <li><code>zookeeper.ssl.cipher.suites</code></li>
                <li><code>zookeeper.ssl.endpoint.identification.algorithm</code></li>
                <li><code>zookeeper.ssl.crl.enable</code></li>
                <li><code>zookeeper.ssl.ocsp.enable</code></li>
            </ul>
        </li>
    </ul>
    <h5 class="anchor-heading">Removal metrics</h5>
    <ul>
        <li>
            <p>
                Remove the following metrics related to ZooKeeper.
                <code>ControlPlaneNetworkProcessorAvgIdlePercent</code>
                is to monitor the average fraction of time the network processors are idle. The other <code>ControlPlaneExpiredConnectionsKilledCount</code>
                is to monitor the total number of connections disconnected, across all processors.
            </p>
            <ul>
                <li><code>ControlPlaneNetworkProcessorAvgIdlePercent</code></li>
                <li><code>ControlPlaneExpiredConnectionsKilledCount</code></li>
            </ul>
            <p>
                In Kraft mode, Kafka also provides metrics to monitor the network processors and expired connections.
                Use the following metrics to monitor the network processors and expired connections:
            </p>
            <ul>
                <li><code>NetworkProcessorAvgIdlePercent</code></li>
                <li><code>ExpiredConnectionsKilledCount</code></li>
            </ul>
        </li>
        <li>
            <p>
                Remove the metrics which is monitoring the latency in milliseconds for ZooKeeper requests from broker.
            </p>
            <ul>
                <li><code>kafka.server:type=ZooKeeperClientMetrics,name=ZooKeeperRequestLatencyMs</code></li>
            </ul>
            <p>
                In Kraft mode, Zookeeper is not used, so the metrics is removed.
            </p>
        </li>
    </ul>
</div>