package org.apache.helix.participant;
/*
* 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.lang.management.ManagementFactory;
import org.apache.helix.ControllerChangeListener;
import org.apache.helix.HelixDataAccessor;
import org.apache.helix.HelixManager;
import org.apache.helix.HelixManagerFactory;
import org.apache.helix.InstanceType;
import org.apache.helix.NotificationContext;
import org.apache.helix.PropertyKey.Builder;
import org.apache.helix.PropertyType;
import org.apache.helix.controller.GenericHelixController;
import org.apache.helix.controller.HelixControllerMain;
import org.apache.helix.controller.restlet.ZKPropertyTransferServer;
import org.apache.helix.model.LeaderHistory;
import org.apache.helix.model.LiveInstance;
import org.apache.log4j.Logger;
// TODO: merge with GenericHelixController
public class DistClusterControllerElection implements ControllerChangeListener {
private static Logger LOG = Logger.getLogger(DistClusterControllerElection.class);
private final String _zkAddr;
private final GenericHelixController _controller = new GenericHelixController();
private HelixManager _leader;
public DistClusterControllerElection(String zkAddr) {
_zkAddr = zkAddr;
}
/**
* may be accessed by multiple threads: zk-client thread and
* ZkHelixManager.disconnect()->reset() TODO: Refactor accessing
* HelixMaangerMain class statically
*/
@Override
public synchronized void onControllerChange(NotificationContext changeContext) {
HelixManager manager = changeContext.getManager();
if (manager == null) {
LOG.error("missing attributes in changeContext. requires HelixManager");
return;
}
InstanceType type = manager.getInstanceType();
if (type != InstanceType.CONTROLLER && type != InstanceType.CONTROLLER_PARTICIPANT) {
LOG.error("fail to become controller because incorrect instanceType (was " + type.toString()
+ ", requires CONTROLLER | CONTROLLER_PARTICIPANT)");
return;
}
try {
if (changeContext.getType().equals(NotificationContext.Type.INIT)
|| changeContext.getType().equals(NotificationContext.Type.CALLBACK)) {
// DataAccessor dataAccessor = manager.getDataAccessor();
HelixDataAccessor accessor = manager.getHelixDataAccessor();
Builder keyBuilder = accessor.keyBuilder();
while (accessor.getProperty(keyBuilder.controllerLeader()) == null) {
boolean success = tryUpdateController(manager);
if (success) {
updateHistory(manager);
if (type == InstanceType.CONTROLLER) {
HelixControllerMain.addListenersToController(manager, _controller);
manager.startTimerTasks();
} else if (type == InstanceType.CONTROLLER_PARTICIPANT) {
String clusterName = manager.getClusterName();
String controllerName = manager.getInstanceName();
_leader =
HelixManagerFactory.getZKHelixManager(clusterName, controllerName,
InstanceType.CONTROLLER, _zkAddr);
_leader.connect();
_leader.startTimerTasks();
HelixControllerMain.addListenersToController(_leader, _controller);
}
}
}
} else if (changeContext.getType().equals(NotificationContext.Type.FINALIZE)) {
if (_leader != null) {
_leader.disconnect();
}
}
} catch (Exception e) {
LOG.error("Exception when trying to become leader", e);
}
}
private boolean tryUpdateController(HelixManager manager) {
// DataAccessor dataAccessor = manager.getDataAccessor();
HelixDataAccessor accessor = manager.getHelixDataAccessor();
Builder keyBuilder = accessor.keyBuilder();
LiveInstance leader = new LiveInstance(manager.getInstanceName());
try {
leader.setLiveInstance(ManagementFactory.getRuntimeMXBean().getName());
// TODO: this session id is not the leader's session id in
// distributed mode
leader.setSessionId(manager.getSessionId());
leader.setHelixVersion(manager.getVersion());
if (ZKPropertyTransferServer.getInstance() != null) {
String zkPropertyTransferServiceUrl =
ZKPropertyTransferServer.getInstance().getWebserviceUrl();
if (zkPropertyTransferServiceUrl != null) {
leader.setWebserviceUrl(zkPropertyTransferServiceUrl);
}
} else {
LOG.warn("ZKPropertyTransferServer instnace is null");
}
boolean success = accessor.createProperty(keyBuilder.controllerLeader(), leader);
if (success) {
return true;
} else {
LOG.info("Unable to become leader probably because some other controller becames the leader");
}
} catch (Exception e) {
LOG.error(
"Exception when trying to updating leader record in cluster:" + manager.getClusterName()
+ ". Need to check again whether leader node has been created or not", e);
}
leader = accessor.getProperty(keyBuilder.controllerLeader());
if (leader != null) {
String leaderSessionId = leader.getTypedSessionId().stringify();
LOG.info("Leader exists for cluster: " + manager.getClusterName() + ", currentLeader: "
+ leader.getInstanceName() + ", leaderSessionId: " + leaderSessionId);
if (leaderSessionId != null && leaderSessionId.equals(manager.getSessionId())) {
return true;
}
}
return false;
}
private void updateHistory(HelixManager manager) {
HelixDataAccessor accessor = manager.getHelixDataAccessor();
Builder keyBuilder = accessor.keyBuilder();
LeaderHistory history = accessor.getProperty(keyBuilder.controllerLeaderHistory());
if (history == null) {
history = new LeaderHistory(PropertyType.HISTORY.toString());
}
history.updateHistory(manager.getClusterName(), manager.getInstanceName());
accessor.setProperty(keyBuilder.controllerLeaderHistory(), history);
}
}