/**
* 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.activemq.transport.discovery.http;
import java.io.IOException;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Scanner;
import java.util.Set;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicReference;
import org.apache.activemq.Service;
import org.apache.activemq.command.DiscoveryEvent;
import org.apache.activemq.transport.discovery.DiscoveryAgent;
import org.apache.activemq.transport.discovery.DiscoveryListener;
import org.apache.activemq.util.IntrospectionSupport;
import org.apache.activemq.util.Suspendable;
import org.apache.http.client.HttpClient;
import org.apache.http.client.ResponseHandler;
import org.apache.http.client.methods.HttpDelete;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPut;
import org.apache.http.impl.client.BasicResponseHandler;
import org.apache.http.impl.client.DefaultHttpClient;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
public class HTTPDiscoveryAgent implements DiscoveryAgent, Suspendable {
static enum UpdateState {
SUSPENDED,
RESUMING,
RESUMED
}
private static final Logger LOG = LoggerFactory.getLogger(HTTPDiscoveryAgent.class);
private String registryURL = "http://localhost:8080/discovery-registry/default";
private HttpClient httpClient = new DefaultHttpClient();
private AtomicBoolean running = new AtomicBoolean();
private final AtomicReference<DiscoveryListener> discoveryListener = new AtomicReference<DiscoveryListener>();
private final HashSet<String> registeredServices = new HashSet<String>();
private final HashMap<String, SimpleDiscoveryEvent> discoveredServices = new HashMap<String, SimpleDiscoveryEvent>();
private Thread thread;
private long updateInterval = 1000 * 10;
@SuppressWarnings("unused")
private String brokerName;
private boolean startEmbeddRegistry = false;
private Service jetty;
private 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;
private final Object sleepMutex = new Object();
private final Object updateMutex = new Object();
private UpdateState updateState = UpdateState.RESUMED;
private long minConnectTime = 5000;
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 String getGroup() {
return null;
}
public void registerService(String service) throws IOException {
synchronized (registeredServices) {
registeredServices.add(service);
}
doRegister(service);
}
synchronized private void doRegister(String service) {
String url = registryURL;
try {
HttpPut method = new HttpPut(url);
method.addHeader("service", service);
ResponseHandler<String> handler = new BasicResponseHandler();
String responseBody = httpClient.execute(method, handler);
LOG.debug("PUT to " + url + " got a " + responseBody);
} catch (Exception e) {
LOG.debug("PUT to " + url + " failed with: " + e);
}
}
@SuppressWarnings("unused")
synchronized private void doUnRegister(String service) {
String url = registryURL;
try {
HttpDelete method = new HttpDelete(url);
method.addHeader("service", service);
ResponseHandler<String> handler = new BasicResponseHandler();
String responseBody = httpClient.execute(method, handler);
LOG.debug("DELETE to " + url + " got a " + responseBody);
} catch (Exception e) {
LOG.debug("DELETE to " + url + " failed with: " + e);
}
}
synchronized private Set<String> doLookup(long freshness) {
String url = registryURL + "?freshness=" + freshness;
try {
HttpGet method = new HttpGet(url);
ResponseHandler<String> handler = new BasicResponseHandler();
String response = httpClient.execute(method, handler);
LOG.debug("GET to " + url + " got a " + response);
Set<String> rc = new HashSet<String>();
Scanner scanner = new Scanner(response);
while (scanner.hasNextLine()) {
String service = scanner.nextLine();
if (service.trim().length() != 0) {
rc.add(service);
}
}
scanner.close();
return rc;
} catch (Exception e) {
LOG.debug("GET to " + url + " failed with: " + e);
return null;
}
}
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 setBrokerName(String brokerName) {
this.brokerName = brokerName;
}
public void setDiscoveryListener(DiscoveryListener discoveryListener) {
this.discoveryListener.set(discoveryListener);
}
public void setGroup(String group) {
}
public void start() throws Exception {
if (startCounter.addAndGet(1) == 1) {
if (startEmbeddRegistry) {
jetty = createEmbeddedJettyServer();
Map<String, Object> props = new HashMap<String, Object>();
props.put("agent", this);
IntrospectionSupport.setProperties(jetty, props);
jetty.start();
}
running.set(true);
thread = new Thread("HTTPDiscovery Agent") {
@Override
public void run() {
while (running.get()) {
try {
update();
synchronized (updateMutex) {
do {
if( updateState == UpdateState.RESUMING ) {
updateState = UpdateState.RESUMED;
} else {
updateMutex.wait(updateInterval);
}
} while( updateState==UpdateState.SUSPENDED && running.get());
}
} catch (InterruptedException e) {
return;
}
}
}
};
thread.setDaemon(true);
thread.start();
}
}
/**
* Create the EmbeddedJettyServer instance via reflection so that we can
* avoid a hard runtime dependency on jetty.
*
* @return
* @throws Exception
*/
private Service createEmbeddedJettyServer() throws Exception {
Class<?> clazz = HTTPDiscoveryAgent.class.getClassLoader().loadClass("org.apache.activemq.transport.discovery.http.EmbeddedJettyServer");
return (Service) clazz.newInstance();
}
private void update() {
// Register all our services...
synchronized (registeredServices) {
for (String service : registeredServices) {
doRegister(service);
}
}
// Find new registered services...
DiscoveryListener discoveryListener = this.discoveryListener.get();
if (discoveryListener != null) {
Set<String> activeServices = doLookup(updateInterval * 3);
// If there is error talking the the central server, then
// activeServices == null
if (activeServices != null) {
synchronized (discoveredServices) {
HashSet<String> removedServices = new HashSet<String>(discoveredServices.keySet());
removedServices.removeAll(activeServices);
HashSet<String> addedServices = new HashSet<String>(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);
}
}
}
}
}
public void stop() throws Exception {
if (startCounter.decrementAndGet() == 0) {
resume();
running.set(false);
if (thread != null) {
thread.join(updateInterval * 3);
thread = null;
}
if (jetty != null) {
jetty.stop();
jetty = null;
}
}
}
public String getRegistryURL() {
return registryURL;
}
public void setRegistryURL(String discoveryRegistryURL) {
this.registryURL = discoveryRegistryURL;
}
public long getUpdateInterval() {
return updateInterval;
}
public void setUpdateInterval(long updateInterval) {
this.updateInterval = updateInterval;
}
public boolean isStartEmbeddRegistry() {
return startEmbeddRegistry;
}
public void setStartEmbeddRegistry(boolean startEmbeddRegistry) {
this.startEmbeddRegistry = startEmbeddRegistry;
}
@Override
public void suspend() throws Exception {
synchronized (updateMutex) {
updateState = UpdateState.SUSPENDED;
}
}
@Override
public void resume() throws Exception {
synchronized (updateMutex) {
updateState = UpdateState.RESUMING;
updateMutex.notify();
}
}
}