/**
* Copyright (C) 2012 LinkedIn Inc <opensource@linkedin.com>
*
* 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 com.linkedin.helix.participant;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import org.apache.log4j.Logger;
import com.linkedin.helix.HelixConstants.ChangeType;
import com.linkedin.helix.HelixConstants.StateModelToken;
import com.linkedin.helix.HelixDataAccessor;
import com.linkedin.helix.HelixManager;
import com.linkedin.helix.PropertyKey.Builder;
import com.linkedin.helix.manager.zk.ZKHelixDataAccessor;
import com.linkedin.helix.manager.zk.ZNRecordSerializer;
import com.linkedin.helix.manager.zk.ZkBaseDataAccessor;
import com.linkedin.helix.manager.zk.ZkClient;
import com.linkedin.helix.model.IdealState;
import com.linkedin.helix.model.IdealState.IdealStateModeProperty;
/**
* This provides the ability for users to run a custom code in exactly one
* process using a LeaderStandBy state model. <br/>
* A typical use case is when one uses CUSTOMIZED ideal state mode where the
* assignment of partition to nodes needs to change dynamically as the nodes go
* online/offline.<br/>
* <code>
* HelixCustomCodeRunner runner = new HelixCustomCodeRunner(manager,ZK_ADDR);
* runner
* .invoke(_callback)
* .on(ChangeType.LIVE_INSTANCE, ChangeType.IdealState)
* .usingLeaderStandbyModel("someUniqueId")
* .run()
* </code>
*
* @author kgopalak
*
*/
public class HelixCustomCodeRunner
{
private static final String LEADER_STANDBY = "LeaderStandby";
private static Logger LOG = Logger.getLogger(HelixCustomCodeRunner.class);
private static String PARTICIPANT_LEADER = "PARTICIPANT_LEADER";
private CustomCodeCallbackHandler _callback;
private List<ChangeType> _notificationTypes;
private String _resourceName;
private final HelixManager _manager;
private final String _zkAddr;
private GenericLeaderStandbyStateModelFactory _stateModelFty;
/**
* Constructs a HelixCustomCodeRunner that will run exactly in one place
*
* @param manager
* @param zkAddr
*/
public HelixCustomCodeRunner(HelixManager manager, String zkAddr)
{
_manager = manager;
_zkAddr = zkAddr;
}
/**
* callback to invoke when there is a change in cluster state specified by on(
* notificationTypes) This callback must be idempotent which means they should
* not depend on what changed instead simply read the cluster data and act on
* it.
*
* @param callback
* @return
*/
public HelixCustomCodeRunner invoke(CustomCodeCallbackHandler callback)
{
_callback = callback;
return this;
}
/**
* ChangeTypes interested in, ParticipantLeaderCallback.callback method will
* be invoked on the
*
* @param notificationTypes
* @return
*/
public HelixCustomCodeRunner on(ChangeType... notificationTypes)
{
_notificationTypes = Arrays.asList(notificationTypes);
return this;
}
public HelixCustomCodeRunner usingLeaderStandbyModel(String id)
{
_resourceName = PARTICIPANT_LEADER + "_" + id;
return this;
}
/**
* This method will be invoked when there is a change in any subscribed
* notificationTypes
*
* @throws Exception
*/
public void start() throws Exception
{
if (_callback == null || _notificationTypes == null || _notificationTypes.size() == 0
|| _resourceName == null)
{
throw new IllegalArgumentException("Require callback | notificationTypes | resourceName");
}
LOG.info("Register participantLeader on " + _notificationTypes + " using " + _resourceName);
_stateModelFty = new GenericLeaderStandbyStateModelFactory(_callback, _notificationTypes);
StateMachineEngine stateMach = _manager.getStateMachineEngine();
stateMach.registerStateModelFactory(LEADER_STANDBY, _stateModelFty, _resourceName);
ZkClient zkClient = null;
try
{
// manually add ideal state for participant leader using LeaderStandby
// model
zkClient = new ZkClient(_zkAddr, ZkClient.DEFAULT_CONNECTION_TIMEOUT);
zkClient.setZkSerializer(new ZNRecordSerializer());
HelixDataAccessor accessor = new ZKHelixDataAccessor(_manager.getClusterName(), new ZkBaseDataAccessor(zkClient));
Builder keyBuilder = accessor.keyBuilder();
IdealState idealState = new IdealState(_resourceName);
idealState.setIdealStateMode(IdealStateModeProperty.AUTO.toString());
idealState.setReplicas(StateModelToken.ANY_LIVEINSTANCE.toString());
idealState.setNumPartitions(1);
idealState.setStateModelDefRef(LEADER_STANDBY);
idealState.setStateModelFactoryName(_resourceName);
List<String> prefList = new ArrayList<String>(Arrays.asList(StateModelToken.ANY_LIVEINSTANCE
.toString()));
idealState.getRecord().setListField(_resourceName + "_0", prefList);
List<String> idealStates = accessor.getChildNames(keyBuilder.idealStates());
while (idealStates == null || !idealStates.contains(_resourceName))
{
accessor.setProperty(keyBuilder.idealStates(_resourceName), idealState);
idealStates = accessor.getChildNames(keyBuilder.idealStates());
}
LOG.info("Set idealState for participantLeader:" + _resourceName + ", idealState:"
+ idealState);
} finally
{
if (zkClient != null && zkClient.getConnection() != null)
{
zkClient.close();
}
}
}
/**
* Stop customer code runner
*/
public void stop()
{
LOG.info("Removing stateModelFactory for " + _resourceName);
_manager.getStateMachineEngine().removeStateModelFactory(LEADER_STANDBY, _stateModelFty,
_resourceName);
}
}