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TaskRequestIdGenerator xref
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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one
3    * or more contributor license agreements.  See the NOTICE file
4    * distributed with this work for additional information
5    * regarding copyright ownership.  The ASF licenses this file
6    * to you under the Apache License, Version 2.0 (the
7    * "License"); you may not use this file except in compliance
8    * with the License.  You may obtain a copy of the License at
9    *
10   *     http://www.apache.org/licenses/LICENSE-2.0
11   *
12   * Unless required by applicable law or agreed to in writing, software
13   * distributed under the License is distributed on an "AS IS" BASIS,
14   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15   * See the License for the specific language governing permissions and
16   * limitations under the License.
17   */
18  
19  package org.apache.giraph.comm.netty.handler;
20  
21  import com.google.common.collect.Maps;
22  import java.util.concurrent.ConcurrentMap;
23  import java.util.concurrent.atomic.AtomicLong;
24  
25  /**
26   * Generate different request ids based on the task id.  Thread-safe.
27   */
28  public class TaskRequestIdGenerator {
29    /** Task request generator map */
30    private final ConcurrentMap<Integer, AtomicLong>
31        taskRequestGeneratorMap = Maps.newConcurrentMap();
32  
33    /**
34     * Get the next request id for a given destination.  Thread-safe.
35     *
36     * @param taskId id of the task(consistent during a superstep)
37     * @return Valid request id
38     */
39    public Long getNextRequestId(Integer taskId) {
40      AtomicLong requestGenerator = taskRequestGeneratorMap.get(taskId);
41      if (requestGenerator == null) {
42        requestGenerator = new AtomicLong(0);
43        AtomicLong oldRequestGenerator =
44            taskRequestGeneratorMap.putIfAbsent(taskId, requestGenerator);
45        if (oldRequestGenerator != null) {
46          requestGenerator = oldRequestGenerator;
47        }
48      }
49      return requestGenerator.getAndIncrement();
50    }
51  }