/*

  * 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.

  */

 package org.apache.giraph.bsp;

 import java.io.IOException;

 import org.apache.giraph.graph.MasterAggregatorUsage;

 import org.apache.hadoop.io.Writable;

 import org.apache.hadoop.io.WritableComparable;

 import org.apache.zookeeper.KeeperException;

 /**

  * At most, there will be one active master at a time, but many threads can

  * be trying to be the active master.

  *

  * @param <I> Vertex id

  * @param <V> Vertex value

  * @param <E> Edge value

  * @param <M> Message data

  */

 @SuppressWarnings("rawtypes")

 public interface CentralizedServiceMaster<I extends WritableComparable,

     V extends Writable, E extends Writable, M extends Writable> extends

     CentralizedService<I, V, E, M>, MasterAggregatorUsage {

   /**

    * Become the master.

    * @return true if became the master, false if the application is done.

    */

   boolean becomeMaster();

   /**

    * Create the {@link InputSplit} objects from the index range based on the

    * user-defined VertexInputFormat.  The {@link InputSplit} objects will

    * processed by the workers later on during the INPUT_SUPERSTEP.

    *

    * @return Number of partitions. Returns -1 on failure to create

    *         valid input splits.

    */

   int createInputSplits();

   /**

    * Master coordinates the superstep

    *

    * @return State of the application as a result of this superstep

    * @throws InterruptedException

    * @throws KeeperException

    */

   SuperstepState coordinateSuperstep()

     throws KeeperException, InterruptedException;

   /**

    * Master can decide to restart from the last good checkpoint if a

    * worker fails during a superstep.

    *

    * @param checkpoint Checkpoint to restart from

    */

   void restartFromCheckpoint(long checkpoint);

   /**

    * Get the last known good checkpoint

    *

    * @return Last good superstep number

    * @throws IOException

    */

   long getLastGoodCheckpoint() throws IOException;

   /**

    * If the master decides that this job doesn't have the resources to

    * continue, it can fail the job.  It can also designate what to do next.

    * Typically this is mainly informative.

    *

    * @param state State of the application.

    * @param applicationAttempt Attempt to start on

    * @param desiredSuperstep Superstep to restart from (if applicable)

    */

   void setJobState(ApplicationState state,

     long applicationAttempt,

     long desiredSuperstep);

 }