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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.aggregators;
20  
21  import com.google.common.collect.Maps;
22  
23  import java.util.Map;
24  
25  /**
26   * Cache which counts the number of flushes per task id (destination worker
27   * id), so we know how many requests were sent to the worker
28   */
29  public abstract class CountingCache {
30    /** Counts the number of flushes for each worker */
31    private Map<Integer, Long> countMap = Maps.newHashMap();
32  
33    /**
34     * Increase count of flushes for worker with desired task id. Subclasses
35     * should call this method whenever flush is called.
36     *
37     * @param taskId Task id of worker
38     */
39    protected void incrementCounter(Integer taskId) {
40      Long currentCount = countMap.get(taskId);
41      countMap.put(taskId,
42          (currentCount == null) ? 1 : (currentCount + 1));
43    }
44  
45    /**
46     * Get number of flushes for worker with desired task id
47     *
48     * @param taskId Task id of worker
49     * @return Number of objects for the worker
50     */
51    protected long getCount(Integer taskId) {
52      Long count = countMap.get(taskId);
53      if (count == null) {
54        return 0;
55      } else {
56        return count.longValue();
57      }
58    }
59  
60    /**
61     * Reset the counts
62     */
63    public void reset() {
64      countMap.clear();
65    }
66  }