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1   /**
2    * Copyright 2012 The Apache Software Foundation
3    *
4    * Licensed to the Apache Software Foundation (ASF) under one
5    * or more contributor license agreements.  See the NOTICE file
6    * distributed with this work for additional information
7    * regarding copyright ownership.  The ASF licenses this file
8    * to you under the Apache License, Version 2.0 (the
9    * "License"); you may not use this file except in compliance
10   * with the License.  You may obtain a copy of the License at
11   *
12   *     http://www.apache.org/licenses/LICENSE-2.0
13   *
14   * Unless required by applicable law or agreed to in writing, software
15   * distributed under the License is distributed on an "AS IS" BASIS,
16   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
17   * See the License for the specific language governing permissions and
18   * limitations under the License.
19   */
20  package org.apache.hadoop.hbase.master.balancer;
21  
22  import java.util.List;
23  import java.util.Map;
24  
25  import org.apache.commons.logging.Log;
26  import org.apache.commons.logging.LogFactory;
27  import org.apache.hadoop.classification.InterfaceAudience;
28  import org.apache.hadoop.hbase.HRegionInfo;
29  import org.apache.hadoop.hbase.ServerName;
30  import org.jboss.netty.util.internal.ConcurrentHashMap;
31  
32  /**
33   * This class contains the mapping information between each region and
34   * its favored region server list. Used by {@link FavoredNodeLoadBalancer} set
35   * of classes and from unit tests (hence the class is public)
36   *
37   * All the access to this class is thread-safe.
38   */
39  @InterfaceAudience.Private
40  public class FavoredNodes {
41    protected static final Log LOG = LogFactory.getLog(
42        FavoredNodes.class.getName());
43  
44    /** the map between each region and its favored region server list */
45    private Map<HRegionInfo, List<ServerName>> favoredNodesMap;
46  
47    public static enum Position {
48      PRIMARY,
49      SECONDARY,
50      TERTIARY;
51    };
52  
53    public FavoredNodes() {
54      favoredNodesMap = new ConcurrentHashMap<HRegionInfo, List<ServerName>>();
55    }
56  
57    /**
58     * Add an assignment to the plan
59     * @param region
60     * @param servers
61     */
62    public synchronized void updateFavoredNodesMap(HRegionInfo region,
63        List<ServerName> servers) {
64      if (region == null || servers == null || servers.size() ==0)
65        return;
66      this.favoredNodesMap.put(region, servers);
67    }
68  
69    /**
70     * @param region
71     * @return the list of favored region server for this region based on the plan
72     */
73    public synchronized List<ServerName> getFavoredNodes(HRegionInfo region) {
74      return favoredNodesMap.get(region);
75    }
76  
77    /**
78     * Return the position of the server in the favoredNodes list. Assumes the
79     * favoredNodes list is of size 3.
80     * @param favoredNodes
81     * @param server
82     * @return position
83     */
84    static Position getFavoredServerPosition(
85        List<ServerName> favoredNodes, ServerName server) {
86      if (favoredNodes == null || server == null ||
87          favoredNodes.size() != FavoredNodeAssignmentHelper.FAVORED_NODES_NUM) {
88        return null;
89      }
90      for (Position p : Position.values()) {
91        if (favoredNodes.get(p.ordinal()).equals(server)) {
92          return p;
93        }
94      }
95      return null;
96    }
97  }