helix-core/src/main/java/org/apache/helix/examples/BootstrapHandler.java

package org.apache.helix.examples;

/*
 * 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.UUID;

import org.apache.helix.ClusterMessagingService;
import org.apache.helix.Criteria;
import org.apache.helix.HelixManager;
import org.apache.helix.InstanceType;
import org.apache.helix.NotificationContext;
import org.apache.helix.model.Message;
import org.apache.helix.model.Message.MessageState;
import org.apache.helix.model.Message.MessageType;
import org.apache.helix.participant.statemachine.StateModel;
import org.apache.helix.participant.statemachine.StateModelFactory;
import org.apache.helix.participant.statemachine.StateModelInfo;
import org.apache.helix.participant.statemachine.Transition;

public class BootstrapHandler extends StateModelFactory<StateModel> {

  @Override
  public StateModel createNewStateModel(String resourceName, String stateUnitKey) {
    return new BootstrapStateModel(stateUnitKey);
  }

  @StateModelInfo(initialState = "OFFLINE", states = "{'OFFLINE','SLAVE','MASTER'}")
  public static class BootstrapStateModel extends StateModel {

    private final String _stateUnitKey;

    public BootstrapStateModel(String stateUnitKey) {
      _stateUnitKey = stateUnitKey;

    }

    @Transition(from = "MASTER", to = "SLAVE")
    public void masterToSlave(Message message, NotificationContext context) {

    }

    @Transition(from = "OFFLINE", to = "SLAVE")
    public void offlineToSlave(Message message, NotificationContext context) {
      System.out.println("BootstrapProcess.BootstrapStateModel.offlineToSlave()");
      HelixManager manager = context.getManager();
      ClusterMessagingService messagingService = manager.getMessagingService();
      Message requestBackupUriRequest =
          new Message(MessageType.USER_DEFINE_MSG, UUID.randomUUID().toString());
      requestBackupUriRequest.setMsgSubType(BootstrapProcess.REQUEST_BOOTSTRAP_URL);
      requestBackupUriRequest.setMsgState(MessageState.NEW);
      Criteria recipientCriteria = new Criteria();
      recipientCriteria.setInstanceName("*");
      recipientCriteria.setRecipientInstanceType(InstanceType.PARTICIPANT);
      recipientCriteria.setResource(message.getResourceName());
      recipientCriteria.setPartition(message.getPartitionName());
      recipientCriteria.setSessionSpecific(true);
      // wait for 30 seconds
      int timeout = 30000;
      BootstrapReplyHandler responseHandler = new BootstrapReplyHandler();

      int sentMessageCount =
          messagingService.sendAndWait(recipientCriteria, requestBackupUriRequest, responseHandler,
              timeout);
      if (sentMessageCount == 0) {
        // could not find any other node hosting the partition
      } else if (responseHandler.getBootstrapUrl() != null) {
        System.out.println("Got bootstrap url:" + responseHandler.getBootstrapUrl());
        System.out.println("Got backup time:" + responseHandler.getBootstrapTime());
        // Got the url fetch it
      } else {
        // Either go to error state
        // throw new Exception("Cant find backup/bootstrap data");
        // Request some node to start backup process
      }
    }

    @Transition(from = "SLAVE", to = "OFFLINE")
    public void slaveToOffline(Message message, NotificationContext context) {
      System.out.println("BootstrapProcess.BootstrapStateModel.slaveToOffline()");
    }

    @Transition(from = "SLAVE", to = "MASTER")
    public void slaveToMaster(Message message, NotificationContext context) {
      System.out.println("BootstrapProcess.BootstrapStateModel.slaveToMaster()");
    }

  }
}