helix-core/src/main/java/org/apache/helix/participant/GenericLeaderStandbyModel.java

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.List;

import org.apache.helix.HelixManager;
import org.apache.helix.NotificationContext;
import org.apache.helix.HelixConstants.ChangeType;
import org.apache.helix.PropertyKey.Builder;
import org.apache.helix.model.Message;
import org.apache.helix.participant.statemachine.StateModel;
import org.apache.helix.participant.statemachine.StateModelInfo;
import org.apache.helix.participant.statemachine.Transition;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

@StateModelInfo(initialState = "OFFLINE", states = {
    "LEADER", "STANDBY"
})
public class GenericLeaderStandbyModel extends StateModel {
  private static Logger LOG = LoggerFactory.getLogger(GenericLeaderStandbyModel.class);

  private final CustomCodeInvoker _particHolder;
  private final List<ChangeType> _notificationTypes;

  public GenericLeaderStandbyModel(CustomCodeCallbackHandler callback,
      List<ChangeType> notificationTypes, String partitionKey) {
    _particHolder = new CustomCodeInvoker(callback, partitionKey);
    _notificationTypes = notificationTypes;
  }

  @Transition(to = "STANDBY", from = "OFFLINE")
  public void onBecomeStandbyFromOffline(Message message, NotificationContext context) {
    LOG.info("Become STANDBY from OFFLINE");
  }

  @Transition(to = "LEADER", from = "STANDBY")
  public void onBecomeLeaderFromStandby(Message message, NotificationContext context)
      throws Exception {
    LOG.info("Become LEADER from STANDBY");
    HelixManager manager = context.getManager();
    if (manager == null) {
      throw new IllegalArgumentException("Require HelixManager in notification conext");
    }
    for (ChangeType notificationType : _notificationTypes) {
      if (notificationType == ChangeType.LIVE_INSTANCE) {
        manager.addLiveInstanceChangeListener(_particHolder);
      } else if (notificationType == ChangeType.CONFIG) {
        manager.addConfigChangeListener(_particHolder);
      } else if (notificationType == ChangeType.EXTERNAL_VIEW) {
        manager.addExternalViewChangeListener(_particHolder);
      } else {
        LOG.error("Unsupport notificationType:" + notificationType.toString());
      }
    }
  }

  @Transition(to = "STANDBY", from = "LEADER")
  public void onBecomeStandbyFromLeader(Message message, NotificationContext context) {
    LOG.info("Become STANDBY from LEADER");
    HelixManager manager = context.getManager();
    if (manager == null) {
      throw new IllegalArgumentException("Require HelixManager in notification conext");
    }

    Builder keyBuilder = new Builder(manager.getClusterName());
    for (ChangeType notificationType : _notificationTypes) {
      if (notificationType == ChangeType.LIVE_INSTANCE) {
        manager.removeListener(keyBuilder.liveInstances(), _particHolder);
      } else if (notificationType == ChangeType.CONFIG) {
        manager.removeListener(keyBuilder.instanceConfigs(), _particHolder);
      } else if (notificationType == ChangeType.EXTERNAL_VIEW) {
        manager.removeListener(keyBuilder.externalViews(), _particHolder);
      } else {
        LOG.error("Unsupport notificationType:" + notificationType.toString());
      }
    }
  }

  @Transition(to = "OFFLINE", from = "STANDBY")
  public void onBecomeOfflineFromStandby(Message message, NotificationContext context) {
    LOG.info("Become OFFLINE from STANDBY");
  }
}