Package org.apache.helix.participant

Source Code of org.apache.helix.participant.HelixCustomCodeRunner

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.util.ArrayList;
import java.util.Arrays;
import java.util.List;

import org.apache.helix.HelixDataAccessor;
import org.apache.helix.HelixManager;
import org.apache.helix.HelixConstants.ChangeType;
import org.apache.helix.HelixConstants.StateModelToken;
import org.apache.helix.PropertyKey.Builder;
import org.apache.helix.manager.zk.ZKHelixDataAccessor;
import org.apache.helix.manager.zk.ZNRecordSerializer;
import org.apache.helix.manager.zk.ZkBaseDataAccessor;
import org.apache.helix.manager.zk.ZkClient;
import org.apache.helix.model.IdealState;
import org.apache.helix.model.IdealState.IdealStateModeProperty;
import org.apache.log4j.Logger;


/**
* 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>
*
*
*/
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);
  }
}
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