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 */
018package org.apache.hadoop.hdfs.server.balancer;
019
020import org.apache.hadoop.net.NetworkTopology;
021import org.apache.hadoop.net.Node;
022
023/** A matcher interface for matching nodes. */
024public 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}