/*

  * 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.comm.netty.handler;

 import org.apache.giraph.comm.netty.NettyServer;

 import org.apache.giraph.conf.GiraphConstants;

 import org.apache.giraph.utils.IncreasingBitSet;

 import org.apache.hadoop.conf.Configuration;

 import com.google.common.collect.MapMaker;

 import java.util.concurrent.ConcurrentMap;

 /**

  * Provides a thread-safe map for checking worker and request id pairs

  */

 public class WorkerRequestReservedMap {

   /** Map of the worker ids to the requests received (bit set) */

   private final ConcurrentMap<Integer, IncreasingBitSet>

   workerRequestReservedMap;

   /**

    * Constructor

    *

    * @param conf Configuration

    */

   public WorkerRequestReservedMap(Configuration conf) {

     workerRequestReservedMap = new MapMaker().concurrencyLevel(

         conf.getInt(GiraphConstants.MSG_NUM_FLUSH_THREADS,

             NettyServer.MAXIMUM_THREAD_POOL_SIZE_DEFAULT)).makeMap();

   }

   /**

    * Reserve the request (before the request starts to insure that it is

    * only executed once).  We are assuming no failure on the server.

    *

    * @param workerId workerId of the request

    * @param requestId Request id

    * @return True if the reserving succeeded, false otherwise

    */

   public boolean reserveRequest(Integer workerId, long requestId) {

     IncreasingBitSet requestSet = getRequestSet(workerId);

     return requestSet.add(requestId);

   }

   /**

    * Get and create the entry as necessary to get the request bit set.

    *

    * @param workerId Id of the worker to get the bit set for

    * @return Bit set for the worker

    */

   private IncreasingBitSet getRequestSet(Integer workerId) {

     IncreasingBitSet requestSet = workerRequestReservedMap.get(workerId);

     if (requestSet == null) {

       requestSet = new IncreasingBitSet();

       IncreasingBitSet previous =

           workerRequestReservedMap.putIfAbsent(workerId, requestSet);

       if (previous != null) {

         requestSet = previous;

       }

     }

     return requestSet;

   }

 }