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Java implementation of Raft Consensus, this module contains only the core algorithm, and does not have any dependency except Java SE 8, for interface implementations that required by this module, please checkout jraft-ext module

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/**
 *
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  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 net.data.technology.jraft;

import java.nio.ByteBuffer;
import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;

/**
 * Cluster configuration, a class to hold the cluster configuration information
 * @author Data Technology LLC
 *
 */
public class ClusterConfiguration {

    private long logIndex;
    private long lastLogIndex;
    private List servers;

    public ClusterConfiguration(){
        this.servers = new LinkedList();
        this.logIndex = 0;
        this.lastLogIndex = 0;
    }

    /**
     * De-serialize the data stored in buffer to cluster configuration
     * this is used for the peers to get the cluster configuration from log entry value
     * @param buffer the binary data
     * @return cluster configuration
     */
    public static ClusterConfiguration fromBytes(ByteBuffer buffer){
        ClusterConfiguration configuration = new ClusterConfiguration();
        configuration.setLogIndex(buffer.getLong());
        configuration.setLastLogIndex(buffer.getLong());
        while(buffer.hasRemaining()){
            configuration.getServers().add(new ClusterServer(buffer));
        }

        return configuration;
    }

    /**
     * De-serialize the data stored in buffer to cluster configuration
     * this is used for the peers to get the cluster configuration from log entry value
     * @param data the binary data
     * @return cluster configuration
     */
    public static ClusterConfiguration fromBytes(byte[] data){
        return fromBytes(ByteBuffer.wrap(data));
    }

    public long getLogIndex() {
        return logIndex;
    }

    public void setLogIndex(long logIndex) {
        this.logIndex = logIndex;
    }

    /**
     * Gets the log index that contains the previous cluster configuration
     * @return log index
     */
    public long getLastLogIndex() {
        return lastLogIndex;
    }

    public void setLastLogIndex(long lastLogIndex) {
        this.lastLogIndex = lastLogIndex;
    }

    public List getServers() {
        return servers;
    }

    /**
     * Try to get a cluster server configuration from cluster configuration
     * @param id the server id
     * @return a cluster server configuration or null if id is not found
     */
    public ClusterServer getServer(int id){
        for(ClusterServer server : this.servers){
            if(server.getId() == id){
                return server;
            }
        }

        return null;
    }

    /**
     * Serialize the cluster configuration into a buffer
     * this is used for the leader to serialize a new cluster configuration and replicate to peers
     * @return binary data that represents the cluster configuration
     */
    public byte[] toBytes(){
        int totalSize = Long.BYTES * 2;
        List serversData = new ArrayList(this.servers.size());
        for(int i = 0; i < this.servers.size(); ++i){
            ClusterServer server = this.servers.get(i);
            byte[] dataForServer = server.toBytes();
            totalSize += dataForServer.length;
            serversData.add(dataForServer);
        }

        ByteBuffer buffer = ByteBuffer.allocate(totalSize);
        buffer.putLong(this.logIndex);
        buffer.putLong(this.lastLogIndex);
        for(int i = 0; i < serversData.size(); ++i){
            buffer.put(serversData.get(i));
        }

        return buffer.array();
    }
}