org.nebulaframework.grid.cluster.manager.services.heartbeat.HeartBeatTracker.java Source code

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Here is the source code for org.nebulaframework.grid.cluster.manager.services.heartbeat.HeartBeatTracker.java

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/*
 * Copyright (C) 2008 Yohan Liyanage. 
 * 
 * Licensed 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.nebulaframework.grid.cluster.manager.services.heartbeat;

import java.util.UUID;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.nebulaframework.grid.cluster.manager.ClusterManager;
import org.nebulaframework.grid.service.message.ServiceMessage;
import org.nebulaframework.grid.service.message.ServiceMessageType;

/**
 * HeartBeatTracker keeps track of HeartBeats from a specific
 * {@code GridNode}, and if more than {@link ClusterHeartBeatService#MAX_MISS}
 * heartbeats are missed, it dispatches a {@link ServiceMessage}
 * notifying that a {@link ServiceMessageType#HEARTBEAT_FAILED} has
 * occurred for the given {@code GridNode}.
 * 
 * @author Yohan Liyanage
 * @version 1.0
 */
class HeartBeatTracker implements Runnable {

    private static Log log = LogFactory.getLog(HeartBeatTracker.class);

    private UUID nodeId;
    private long lastBeat = System.currentTimeMillis();
    private int missed = 0;
    private boolean stopped = false;

    /**
     * Constructs a {@code HeartBeatTracker} which is to
     * track the heartbeats from a {@code GridNode} with
     * given nodeId
     * 
     * @param nodeId {@code GridNode} id
     */
    public HeartBeatTracker(UUID nodeId) {
        super();
        this.nodeId = nodeId;

    }

    /**
     * Checks for HeartBeats and notifies if heartbeats 
     * have missed for more than {@link ClusterHeartBeatService#MAX_MISS}.
     * <p>
     * Executed on a separate thread.
     */
    public void run() {
        while (!stopped) {

            // Remember time before sleeping
            long sleepTime = System.currentTimeMillis();

            try {
                // Sleep for BEAT_PERIOD
                Thread.sleep(ClusterHeartBeatService.BEAT_PERIOD);
            } catch (InterruptedException e) {
                log.warn("Heartbeat Sleep Interrupted", e);
                continue;
            }

            // Check if stopped during sleep
            if (stopped)
                break;

            // If no new beat during sleep time
            if (lastBeat - sleepTime < 0) {

                missed++;

                // If  missed more than MAX_MISS, notify
                if (missed > ClusterHeartBeatService.MAX_MISS) {
                    ServiceMessage message = new ServiceMessage(nodeId.toString(),
                            ServiceMessageType.HEARTBEAT_FAILED);
                    ClusterManager.getInstance().getServiceMessageSender().sendServiceMessage(message);
                    log.warn("[Heartbeat] Heartbeat Failed on " + nodeId.toString());
                    stop();
                }
            }

        }
    }

    /**
     * Invoked to notify that a new heartbeat has received
     * from the {@code GridNode} of this {@code HeartBeatTracker}.
     */
    public void notifyBeat() {
        lastBeat = System.currentTimeMillis();
        missed = 0;
    }

    /**
     * Starts the {@code HeartBeatTracker}.
     */
    public void start() {
        Thread beatThread = new Thread(this, "HeartBeatTracker-" + nodeId.toString());
        beatThread.setDaemon(true);
        beatThread.setPriority(Thread.MAX_PRIORITY);
        beatThread.start();
        log.debug("[HeartBeat] Started Tracking : " + nodeId);
    }

    /**
     * Stops the {@code HeartBeatTracker}.
     */
    public void stop() {
        log.debug("[HeartBeat] Stopped Tracking : " + nodeId);
        this.stopped = true;
    }

}