001    /**
002     * Licensed to the Apache Software Foundation (ASF) under one
003     * or more contributor license agreements.  See the NOTICE file
004     * distributed with this work for additional information
005     * regarding copyright ownership.  The ASF licenses this file
006     * to you under the Apache License, Version 2.0 (the
007     * "License"); you may not use this file except in compliance
008     * with the License.  You may obtain a copy of the License at
009     *
010     *     http://www.apache.org/licenses/LICENSE-2.0
011     *
012     * Unless required by applicable law or agreed to in writing, software
013     * distributed under the License is distributed on an "AS IS" BASIS,
014     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015     * See the License for the specific language governing permissions and
016     * limitations under the License.
017     */
018    package org.apache.hadoop.hdfs.server.balancer;
019    
020    import org.apache.hadoop.net.NetworkTopology;
021    import org.apache.hadoop.net.Node;
022    
023    /** A matcher interface for matching nodes. */
024    public interface Matcher {
025      /** Given the cluster topology, does the left node match the right node? */
026      public boolean match(NetworkTopology cluster, Node left,  Node right);
027    
028      /** Match datanodes in the same node group. */
029      public static final Matcher SAME_NODE_GROUP = new Matcher() {
030        @Override
031        public boolean match(NetworkTopology cluster, Node left, Node right) {
032          return cluster.isOnSameNodeGroup(left, right);
033        }
034    
035        @Override
036        public String toString() {
037          return "SAME_NODE_GROUP";
038        }
039      };
040    
041      /** Match datanodes in the same rack. */
042      public static final Matcher SAME_RACK = new Matcher() {
043        @Override
044        public boolean match(NetworkTopology cluster, Node left, Node right) {
045          return cluster.isOnSameRack(left, right);
046        }
047    
048        @Override
049        public String toString() {
050          return "SAME_RACK";
051        }
052      };
053    
054      /** Match any datanode with any other datanode. */
055      public static final Matcher ANY_OTHER = new Matcher() {
056        @Override
057        public boolean match(NetworkTopology cluster, Node left, Node right) {
058          return left != right;
059        }
060    
061        @Override
062        public String toString() {
063          return "ANY_OTHER";
064        }
065      };
066    }