/*

  * 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.partition;

 import java.util.Collection;

 import org.apache.hadoop.io.Writable;

 import org.apache.hadoop.io.WritableComparable;

 import org.apache.giraph.worker.WorkerInfo;

 /**

  * Determines how to divide the graph into partitions, how to manipulate

  * partitions and then how to assign those partitions to workers.

  *

  * @param <I> Vertex index value

  * @param <V> Vertex value

  * @param <E> Edge value

  */

 @SuppressWarnings("rawtypes")

 public interface MasterGraphPartitioner<I extends WritableComparable,

     V extends Writable, E extends Writable> {

   /**

    * Set some initial partition owners for the graph. Guaranteed to be called

    * prior to the graph being loaded (initial or restart).

    *

    * @param availableWorkerInfos Workers available for partition assignment

    * @param maxWorkers Maximum number of workers

    * @return Collection of generated partition owners.

    */

   Collection<PartitionOwner> createInitialPartitionOwners(

       Collection<WorkerInfo> availableWorkerInfos, int maxWorkers);

   /**

    * Sets partition owners for the graph.

    * Used then loading from checkpoint.

    * @param partitionOwners assigned partition owners.

    */

   void setPartitionOwners(Collection<PartitionOwner> partitionOwners);

   /**

    * After the worker stats have been merged to a single list, the master can

    * use this information to send commands to the workers for any

    * {@link Partition} changes. This protocol is specific to the

    * {@link MasterGraphPartitioner} implementation.

    *

    * @param allPartitionStatsList All partition stats from all workers.

    * @param availableWorkers Workers available for partition assignment

    * @param maxWorkers Maximum number of workers

    * @param superstep Partition owners will be set for this superstep

    * @return Collection of {@link PartitionOwner} objects that changed from

    *         the previous superstep, empty list if no change.

    */

   Collection<PartitionOwner> generateChangedPartitionOwners(

       Collection<PartitionStats> allPartitionStatsList,

       Collection<WorkerInfo> availableWorkers,

       int maxWorkers,

       long superstep);

   /**

    * Get current partition owners at this time.

    *

    * @return Collection of current {@link PartitionOwner} objects

    */

   Collection<PartitionOwner> getCurrentPartitionOwners();

   /**

    * Instantiate the {@link PartitionStats} implementation used to read the

    * worker stats

    *

    * @return Instantiated {@link PartitionStats} object

    */

   PartitionStats createPartitionStats();

 }