package org.apache.helix.servicediscovery;
/*
* 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.
*/
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Timer;
import java.util.TimerTask;
import org.apache.helix.HelixDataAccessor;
import org.apache.helix.HelixManager;
import org.apache.helix.HelixManagerFactory;
import org.apache.helix.InstanceType;
import org.apache.helix.LiveInstanceChangeListener;
import org.apache.helix.LiveInstanceInfoProvider;
import org.apache.helix.NotificationContext;
import org.apache.helix.PropertyKey;
import org.apache.helix.PropertyKey.Builder;
import org.apache.helix.ZNRecord;
import org.apache.helix.manager.zk.ZKHelixManager;
import org.apache.helix.model.HelixConfigScope;
import org.apache.helix.model.HelixConfigScope.ConfigScopeProperty;
import org.apache.helix.model.LiveInstance;
import org.apache.helix.model.builder.HelixConfigScopeBuilder;
public class ServiceDiscovery {
private final String zkAddress;
private final String cluster;
private HelixManager admin;
List<ServiceMetadata> cache;
static int DEFAULT_POLL_INTERVAL = 30 * 1000; // in ms
private final Mode mode;
Map<String, HelixManager> serviceMap;
private Timer timer;
enum Mode {
NONE, // No monitoring, only registration, on demand reading zk
WATCH, // Watches ZK path
POLL// Polls zk at some intervals
}
public ServiceDiscovery(String zkAddress, String cluster, Mode mode) {
this.zkAddress = zkAddress;
this.cluster = cluster;
this.mode = mode;
serviceMap = new HashMap<String, HelixManager>();
cache = Collections.emptyList();
}
/**
* @return returns true if
*/
public boolean start() throws Exception {
// auto create cluster and allow nodes to automatically join the cluster
admin =
HelixManagerFactory.getZKHelixManager(cluster, "service-discovery",
InstanceType.ADMINISTRATOR, zkAddress);
admin.connect();
admin.getClusterManagmentTool().addCluster(cluster, false);
HelixConfigScope scope =
new HelixConfigScopeBuilder(ConfigScopeProperty.CLUSTER).forCluster(cluster).build();
Map<String, String> properties = new HashMap<String, String>();
properties.put(ZKHelixManager.ALLOW_PARTICIPANT_AUTO_JOIN, String.valueOf(true));
admin.getClusterManagmentTool().setConfig(scope, properties);
switch (mode) {
case POLL:
startBackgroundTask();
break;
case WATCH:
setupWatcher();
break;
case NONE:// dont monitor changes, supports only registration
}
refreshCache();
return true;
}
private void startBackgroundTask() {
TimerTask timertask = new TimerTask() {
@Override
public void run() {
refreshCache();
}
};
timer = new Timer();
timer.scheduleAtFixedRate(timertask, DEFAULT_POLL_INTERVAL, DEFAULT_POLL_INTERVAL);
}
private void setupWatcher() throws Exception {
LiveInstanceChangeListener listener = new LiveInstanceChangeListener() {
@Override
public void onLiveInstanceChange(List<LiveInstance> liveInstances,
NotificationContext changeContext) {
if (changeContext.getType() != NotificationContext.Type.FINALIZE) {
refreshCache();
}
}
};
admin.addLiveInstanceChangeListener(listener);
}
public boolean stop() {
if (admin != null && admin.isConnected()) {
admin.disconnect();
}
if (timer != null) {
timer.cancel();
}
return true;
}
public void deregister(final String serviceId) {
HelixManager helixManager = serviceMap.get(serviceId);
if (helixManager != null && helixManager.isConnected()) {
helixManager.disconnect();
}
}
public boolean register(final String serviceId, final ServiceMetadata serviceMetadata)
throws Exception {
HelixManager helixManager =
HelixManagerFactory.getZKHelixManager(cluster, serviceId, InstanceType.PARTICIPANT,
zkAddress);
LiveInstanceInfoProvider liveInstanceInfoProvider = new LiveInstanceInfoProvider() {
@Override
public ZNRecord getAdditionalLiveInstanceInfo() {
// serialize serviceMetadata to ZNRecord
ZNRecord rec = new ZNRecord(serviceId);
rec.setSimpleField("HOST", serviceMetadata.getHost());
rec.setSimpleField("PORT", String.valueOf(serviceMetadata.getPort()));
rec.setSimpleField("SERVICE_NAME", serviceMetadata.getServiceName());
return rec;
}
};
helixManager.setLiveInstanceInfoProvider(liveInstanceInfoProvider);
helixManager.connect();
serviceMap.put(serviceId, helixManager);
refreshCache();
return true;
}
private void refreshCache() {
Builder propertyKeyBuilder = new PropertyKey.Builder(cluster);
HelixDataAccessor helixDataAccessor = admin.getHelixDataAccessor();
List<LiveInstance> liveInstances =
helixDataAccessor.getChildValues(propertyKeyBuilder.liveInstances());
refreshCache(liveInstances);
}
private void refreshCache(List<LiveInstance> liveInstances) {
List<ServiceMetadata> services = new ArrayList<ServiceMetadata>();
for (LiveInstance liveInstance : liveInstances) {
ServiceMetadata metadata = new ServiceMetadata();
ZNRecord rec = liveInstance.getRecord();
metadata.setPort(Integer.parseInt(rec.getSimpleField("PORT")));
metadata.setHost(rec.getSimpleField("HOST"));
metadata.setServiceName(rec.getSimpleField("SERVICE_NAME"));
services.add(metadata);
}
// protect against multiple threads updating this
synchronized (this) {
cache = services;
}
}
public List<ServiceMetadata> findAllServices() {
if (mode == Mode.NONE) {
refreshCache();
}
return cache;
}
}