/*
    * 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;
    }
  }