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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.hadoop.hbase.master;
20  
21  import org.apache.hadoop.classification.InterfaceAudience;
22  
23  /**
24   * Factory to create MetricsMasterSource when given a  MetricsMasterWrapper
25   */
26  @InterfaceAudience.Private
27  public class MetricsMasterSourceFactoryImpl implements MetricsMasterSourceFactory {
28    private static enum FactoryStorage {
29      INSTANCE;
30      MetricsMasterSource masterSource;
31    }
32  
33    @Override
34    public synchronized MetricsMasterSource create(MetricsMasterWrapper masterWrapper) {
35      if (FactoryStorage.INSTANCE.masterSource == null) {
36        FactoryStorage.INSTANCE.masterSource = new MetricsMasterSourceImpl(masterWrapper);
37      }
38      return FactoryStorage.INSTANCE.masterSource;
39    }
40  }