clients/src/main/java/org/apache/kafka/common/PartitionInfo.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.kafka.common;

/**
 * This is used to describe per-partition state in the MetadataResponse.
 */
public class PartitionInfo {
    private final String topic;
    private final int partition;
    private final Node leader;
    private final Node[] replicas;
    private final Node[] inSyncReplicas;
    private final Node[] offlineReplicas;

    // Used only by tests
    public PartitionInfo(String topic, int partition, Node leader, Node[] replicas, Node[] inSyncReplicas) {
        this(topic, partition, leader, replicas, inSyncReplicas, new Node[0]);
    }

    public PartitionInfo(String topic,
                         int partition,
                         Node leader,
                         Node[] replicas,
                         Node[] inSyncReplicas,
                         Node[] offlineReplicas) {
        this.topic = topic;
        this.partition = partition;
        this.leader = leader;
        this.replicas = replicas;
        this.inSyncReplicas = inSyncReplicas;
        this.offlineReplicas = offlineReplicas;
    }

    /**
     * The topic name
     */
    public String topic() {
        return topic;
    }

    /**
     * The partition id
     */
    public int partition() {
        return partition;
    }

    /**
     * The node id of the node currently acting as a leader for this partition or null if there is no leader
     */
    public Node leader() {
        return leader;
    }

    /**
     * The complete set of replicas for this partition regardless of whether they are alive or up-to-date
     */
    public Node[] replicas() {
        return replicas;
    }

    /**
     * The subset of the replicas that are in sync, that is caught-up to the leader and ready to take over as leader if
     * the leader should fail
     */
    public Node[] inSyncReplicas() {
        return inSyncReplicas;
    }

    /**
     * The subset of the replicas that are offline
     */
    public Node[] offlineReplicas() {
        return offlineReplicas;
    }

    @Override
    public String toString() {
        return String.format("Partition(topic = %s, partition = %d, leader = %s, replicas = %s, isr = %s, offlineReplicas = %s)",
                             topic,
                             partition,
                             leader == null ? "none" : leader.idString(),
                             formatNodeIds(replicas),
                             formatNodeIds(inSyncReplicas),
                             formatNodeIds(offlineReplicas));
    }

    /* Extract the node ids from each item in the array and format for display */
    private String formatNodeIds(Node[] nodes) {
        StringBuilder b = new StringBuilder("[");
        if (nodes != null) {
            for (int i = 0; i < nodes.length; i++) {
                b.append(nodes[i].idString());
                if (i < nodes.length - 1)
                    b.append(',');
            }
        }
        b.append("]");
        return b.toString();
    }

}