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/**
* Copyright (C) 2010-2011, FuseSource Corp. All rights reserved.
*
* http://fusesource.com
*
* The software in this package is published under the terms of the
* CDDL license a copy of which has been included with this distribution
* in the license.txt file.
*/
package org.fusesource.fabric.activemq;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicReference;
import org.apache.activemq.command.DiscoveryEvent;
import org.apache.activemq.transport.discovery.DiscoveryAgent;
import org.apache.activemq.transport.discovery.DiscoveryListener;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.ZooDefs;
import org.apache.zookeeper.data.ACL;
import org.fusesource.fabric.groups.ChangeListener;
import org.fusesource.fabric.groups.Group;
import org.fusesource.fabric.groups.ZooKeeperGroupFactory;
import org.linkedin.util.clock.Timespan;
import org.linkedin.zookeeper.client.IZKClient;
import org.linkedin.zookeeper.client.ZKClient;
public class FabricDiscoveryAgent implements DiscoveryAgent {
private static final Log LOG = LogFactory.getLog(FabricDiscoveryAgent.class);
private IZKClient zkClient;
private List acl = ZooDefs.Ids.OPEN_ACL_UNSAFE;
private Group group;
private String groupName = "default";
private AtomicBoolean running=new AtomicBoolean();
private final AtomicReference discoveryListener = new AtomicReference();
private final HashMap discoveredServices = new HashMap();
private final AtomicInteger startCounter = new AtomicInteger(0);
private long initialReconnectDelay = 1000;
private long maxReconnectDelay = 1000 * 30;
private long backOffMultiplier = 2;
private boolean useExponentialBackOff=true;
private int maxReconnectAttempts = 0;
private final Object sleepMutex = new Object();
private long minConnectTime = 5000;
private String serviceName;
public void setGroupName(String groupName) {
this.groupName = groupName;
}
class SimpleDiscoveryEvent extends DiscoveryEvent {
private int connectFailures;
private long reconnectDelay = initialReconnectDelay;
private long connectTime = System.currentTimeMillis();
private AtomicBoolean failed = new AtomicBoolean(false);
private AtomicBoolean removed = new AtomicBoolean(false);
public SimpleDiscoveryEvent(String service) {
super(service);
}
}
public void registerService(String service) throws IOException {
this.serviceName = service;
if (startCounter.get() == 1) {
group.join(serviceName, serviceName.getBytes("UTF-8"));
}
}
public void serviceFailed(DiscoveryEvent devent) throws IOException {
final SimpleDiscoveryEvent event = (SimpleDiscoveryEvent)devent;
if (event.failed.compareAndSet(false, true)) {
discoveryListener.get().onServiceRemove(event);
if(!event.removed.get()) {
// Setup a thread to re-raise the event...
Thread thread = new Thread() {
public void run() {
// We detect a failed connection attempt because the service
// fails right away.
if (event.connectTime + minConnectTime > System.currentTimeMillis()) {
LOG.debug("Failure occured soon after the discovery event was generated. It will be clasified as a connection failure: "+event);
event.connectFailures++;
if (maxReconnectAttempts > 0 && event.connectFailures >= maxReconnectAttempts) {
LOG.debug("Reconnect attempts exceeded "+maxReconnectAttempts+" tries. Reconnecting has been disabled.");
return;
}
synchronized (sleepMutex) {
try {
if (!running.get() || event.removed.get()) {
return;
}
LOG.debug("Waiting "+event.reconnectDelay+" ms before attepting to reconnect.");
sleepMutex.wait(event.reconnectDelay);
} catch (InterruptedException ie) {
Thread.currentThread().interrupt();
return;
}
}
if (!useExponentialBackOff) {
event.reconnectDelay = initialReconnectDelay;
} else {
// Exponential increment of reconnect delay.
event.reconnectDelay *= backOffMultiplier;
if (event.reconnectDelay > maxReconnectDelay) {
event.reconnectDelay = maxReconnectDelay;
}
}
} else {
event.connectFailures = 0;
event.reconnectDelay = initialReconnectDelay;
}
if (!running.get() || event.removed.get()) {
return;
}
event.connectTime = System.currentTimeMillis();
event.failed.set(false);
discoveryListener.get().onServiceAdd(event);
}
};
thread.setDaemon(true);
thread.start();
}
}
}
public void setDiscoveryListener(DiscoveryListener discoveryListener) {
this.discoveryListener.set(discoveryListener);
}
synchronized public void start() throws Exception {
if( startCounter.addAndGet(1)==1 ) {
running.set(true);
if (zkClient == null) {
ZKClient client = new ZKClient(System.getProperty("zookeeper.url", "localhost:2181"), Timespan.parse("10s"), null);
client.start();
client.waitForStart();
zkClient = client;
}
group = ZooKeeperGroupFactory.create(zkClient, "/fabric/activemq-clusters/" + groupName, acl);
group.add(new ChangeListener() {
public void changed(byte[][] members) {
update(members);
}
});
if (serviceName != null) {
group.join(serviceName, serviceName.getBytes("UTF-8"));
}
}
}
synchronized public void stop() throws Exception {
if( startCounter.decrementAndGet()==0 ) {
running.set(false);
group.close();
zkClient.close();
zkClient = null;
}
}
private void update(byte[][] members) {
// Find new registered services...
DiscoveryListener discoveryListener = this.discoveryListener.get();
if(discoveryListener!=null) {
HashSet activeServices = new HashSet();
for(byte[] m : members) {
try {
activeServices.add(new String(m, "UTF-8"));
} catch (UnsupportedEncodingException e) {
}
}
// If there is error talking the the central server, then activeServices == null
if( members !=null ) {
synchronized(discoveredServices) {
HashSet removedServices = new HashSet(discoveredServices.keySet());
removedServices.removeAll(activeServices);
HashSet addedServices = new HashSet(activeServices);
addedServices.removeAll(discoveredServices.keySet());
addedServices.removeAll(removedServices);
for (String service : addedServices) {
SimpleDiscoveryEvent e = new SimpleDiscoveryEvent(service);
discoveredServices.put(service, e);
discoveryListener.onServiceAdd(e);
}
for (String service : removedServices) {
SimpleDiscoveryEvent e = discoveredServices.remove(service);
if( e !=null ) {
e.removed.set(true);
}
discoveryListener.onServiceRemove(e);
}
}
}
}
}
}