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