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 019package org.apache.hadoop.net; 020 021import org.apache.hadoop.classification.InterfaceAudience; 022import org.apache.hadoop.classification.InterfaceStability; 023import org.apache.hadoop.conf.Configurable; 024import org.apache.hadoop.conf.Configuration; 025import org.apache.hadoop.fs.CommonConfigurationKeys; 026 027import java.util.HashMap; 028import java.util.HashSet; 029import java.util.Map; 030import java.util.Set; 031 032/** 033 * This is a base class for DNS to Switch mappings. <p/> It is not mandatory to 034 * derive {@link DNSToSwitchMapping} implementations from it, but it is strongly 035 * recommended, as it makes it easy for the Hadoop developers to add new methods 036 * to this base class that are automatically picked up by all implementations. 037 * <p/> 038 * 039 * This class does not extend the <code>Configured</code> 040 * base class, and should not be changed to do so, as it causes problems 041 * for subclasses. The constructor of the <code>Configured</code> calls 042 * the {@link #setConf(Configuration)} method, which will call into the 043 * subclasses before they have been fully constructed. 044 * 045 */ 046@InterfaceAudience.Public 047@InterfaceStability.Evolving 048public abstract class AbstractDNSToSwitchMapping 049 implements DNSToSwitchMapping, Configurable { 050 051 private Configuration conf; 052 053 /** 054 * Create an unconfigured instance 055 */ 056 protected AbstractDNSToSwitchMapping() { 057 } 058 059 /** 060 * Create an instance, caching the configuration file. 061 * This constructor does not call {@link #setConf(Configuration)}; if 062 * a subclass extracts information in that method, it must call it explicitly. 063 * @param conf the configuration 064 */ 065 protected AbstractDNSToSwitchMapping(Configuration conf) { 066 this.conf = conf; 067 } 068 069 @Override 070 public Configuration getConf() { 071 return conf; 072 } 073 074 @Override 075 public void setConf(Configuration conf) { 076 this.conf = conf; 077 } 078 079 /** 080 * Predicate that indicates that the switch mapping is known to be 081 * single-switch. The base class returns false: it assumes all mappings are 082 * multi-rack. Subclasses may override this with methods that are more aware 083 * of their topologies. 084 * 085 * <p/> 086 * 087 * This method is used when parts of Hadoop need know whether to apply 088 * single rack vs multi-rack policies, such as during block placement. 089 * Such algorithms behave differently if they are on multi-switch systems. 090 * </p> 091 * 092 * @return true if the mapping thinks that it is on a single switch 093 */ 094 public boolean isSingleSwitch() { 095 return false; 096 } 097 098 /** 099 * Get a copy of the map (for diagnostics) 100 * @return a clone of the map or null for none known 101 */ 102 public Map<String, String> getSwitchMap() { 103 return null; 104 } 105 106 /** 107 * Generate a string listing the switch mapping implementation, 108 * the mapping for every known node and the number of nodes and 109 * unique switches known about -each entry to a separate line. 110 * @return a string that can be presented to the ops team or used in 111 * debug messages. 112 */ 113 public String dumpTopology() { 114 Map<String, String> rack = getSwitchMap(); 115 StringBuilder builder = new StringBuilder(); 116 builder.append("Mapping: ").append(toString()).append("\n"); 117 if (rack != null) { 118 builder.append("Map:\n"); 119 Set<String> switches = new HashSet<String>(); 120 for (Map.Entry<String, String> entry : rack.entrySet()) { 121 builder.append(" ") 122 .append(entry.getKey()) 123 .append(" -> ") 124 .append(entry.getValue()) 125 .append("\n"); 126 switches.add(entry.getValue()); 127 } 128 builder.append("Nodes: ").append(rack.size()).append("\n"); 129 builder.append("Switches: ").append(switches.size()).append("\n"); 130 } else { 131 builder.append("No topology information"); 132 } 133 return builder.toString(); 134 } 135 136 protected boolean isSingleSwitchByScriptPolicy() { 137 return conf != null 138 && conf.get(CommonConfigurationKeys.NET_TOPOLOGY_SCRIPT_FILE_NAME_KEY) == null; 139 } 140 141 /** 142 * Query for a {@link DNSToSwitchMapping} instance being on a single 143 * switch. 144 * <p/> 145 * This predicate simply assumes that all mappings not derived from 146 * this class are multi-switch. 147 * @param mapping the mapping to query 148 * @return true if the base class says it is single switch, or the mapping 149 * is not derived from this class. 150 */ 151 public static boolean isMappingSingleSwitch(DNSToSwitchMapping mapping) { 152 return mapping != null && mapping instanceof AbstractDNSToSwitchMapping 153 && ((AbstractDNSToSwitchMapping) mapping).isSingleSwitch(); 154 } 155 156}