001/** 002 * 003 * Licensed to the Apache Software Foundation (ASF) under one 004 * or more contributor license agreements. See the NOTICE file 005 * distributed with this work for additional information 006 * regarding copyright ownership. The ASF licenses this file 007 * to you under the Apache License, Version 2.0 (the 008 * "License"); you may not use this file except in compliance 009 * with the License. You may obtain a copy of the License at 010 * 011 * http://www.apache.org/licenses/LICENSE-2.0 012 * 013 * Unless required by applicable law or agreed to in writing, software 014 * distributed under the License is distributed on an "AS IS" BASIS, 015 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 016 * See the License for the specific language governing permissions and 017 * limitations under the License. 018 */ 019package org.apache.hadoop.hbase.master; 020 021import edu.umd.cs.findbugs.annotations.NonNull; 022import java.io.IOException; 023import java.util.List; 024import java.util.Map; 025import org.apache.hadoop.conf.Configurable; 026import org.apache.hadoop.conf.Configuration; 027import org.apache.hadoop.hbase.ClusterMetrics; 028import org.apache.hadoop.hbase.HBaseIOException; 029import org.apache.hadoop.hbase.ServerName; 030import org.apache.hadoop.hbase.Stoppable; 031import org.apache.hadoop.hbase.TableName; 032import org.apache.hadoop.hbase.client.RegionInfo; 033import org.apache.hadoop.hbase.conf.ConfigurationObserver; 034import org.apache.yetus.audience.InterfaceAudience; 035 036/** 037 * Makes decisions about the placement and movement of Regions across 038 * RegionServers. 039 * 040 * <p>Cluster-wide load balancing will occur only when there are no regions in 041 * transition and according to a fixed period of a time using {@link #balanceCluster(Map)}. 042 * 043 * <p>On cluster startup, bulk assignment can be used to determine 044 * locations for all Regions in a cluster. 045 * 046 * <p>This class produces plans for the 047 * {@link org.apache.hadoop.hbase.master.assignment.AssignmentManager} 048 * to execute. 049 */ 050@InterfaceAudience.Private 051public interface LoadBalancer extends Configurable, Stoppable, ConfigurationObserver { 052 /** 053 * Master can carry regions as of hbase-2.0.0. 054 * By default, it carries no tables. 055 * TODO: Add any | system as flags to indicate what it can do. 056 * 057 * @deprecated since 2.4.0, will be removed in 3.0.0. 058 * @see <a href="https://issues.apache.org/jira/browse/HBASE-15549">HBASE-15549</a> 059 */ 060 @Deprecated 061 String TABLES_ON_MASTER = "hbase.balancer.tablesOnMaster"; 062 063 /** 064 * Master carries system tables. 065 * 066 * @deprecated since 2.4.0, will be removed in 3.0.0. 067 * @see <a href="https://issues.apache.org/jira/browse/HBASE-15549">HBASE-15549</a> 068 */ 069 @Deprecated 070 String SYSTEM_TABLES_ON_MASTER = "hbase.balancer.tablesOnMaster.systemTablesOnly"; 071 072 // Used to signal to the caller that the region(s) cannot be assigned 073 // We deliberately use 'localhost' so the operation will fail fast 074 ServerName BOGUS_SERVER_NAME = ServerName.valueOf("localhost,1,1"); 075 076 /** 077 * Set the current cluster status. This allows a LoadBalancer to map host name to a server 078 * @param st 079 */ 080 void setClusterMetrics(ClusterMetrics st); 081 082 /** 083 * Set the master service. 084 * @param masterServices 085 */ 086 void setMasterServices(MasterServices masterServices); 087 088 /** 089 * Perform the major balance operation for cluster, will invoke {@link #balanceTable} to do 090 * actual balance. Normally not need override this method, except SimpleLoadBalancer and 091 * RSGroupBasedLoadBalancer. 092 * @param loadOfAllTable region load of servers for all table 093 * @return a list of regions to be moved, including source and destination, or null if cluster is 094 * already balanced 095 */ 096 List<RegionPlan> balanceCluster(Map<TableName, 097 Map<ServerName, List<RegionInfo>>> loadOfAllTable) throws IOException; 098 099 /** 100 * Perform the major balance operation for table, all class implement of {@link LoadBalancer} 101 * should override this method 102 * @param tableName the table to be balanced 103 * @param loadOfOneTable region load of servers for the specific one table 104 * @return List of plans 105 */ 106 List<RegionPlan> balanceTable(TableName tableName, 107 Map<ServerName, List<RegionInfo>> loadOfOneTable); 108 /** 109 * Perform a Round Robin assignment of regions. 110 * @param regions 111 * @param servers 112 * @return Map of servername to regioninfos 113 */ 114 @NonNull 115 Map<ServerName, List<RegionInfo>> roundRobinAssignment(List<RegionInfo> regions, 116 List<ServerName> servers) throws HBaseIOException; 117 118 /** 119 * Assign regions to the previously hosting region server 120 * @param regions 121 * @param servers 122 * @return List of plans 123 */ 124 @NonNull 125 Map<ServerName, List<RegionInfo>> retainAssignment(Map<RegionInfo, ServerName> regions, 126 List<ServerName> servers) throws HBaseIOException; 127 128 /** 129 * Get a random region server from the list 130 * @param regionInfo Region for which this selection is being done. 131 * @param servers 132 * @return Servername 133 */ 134 ServerName randomAssignment( 135 RegionInfo regionInfo, List<ServerName> servers 136 ) throws HBaseIOException; 137 138 /** 139 * Initialize the load balancer. Must be called after setters. 140 * @throws HBaseIOException 141 */ 142 void initialize() throws HBaseIOException; 143 144 /** 145 * Marks the region as online at balancer. 146 * @param regionInfo 147 * @param sn 148 */ 149 void regionOnline(RegionInfo regionInfo, ServerName sn); 150 151 /** 152 * Marks the region as offline at balancer. 153 * @param regionInfo 154 */ 155 void regionOffline(RegionInfo regionInfo); 156 157 /* 158 * Notification that config has changed 159 * @param conf 160 */ 161 @Override 162 void onConfigurationChange(Configuration conf); 163 164 /** 165 * If balancer needs to do initialization after Master has started up, lets do that here. 166 */ 167 void postMasterStartupInitialize(); 168 169 /*Updates balancer status tag reported to JMX*/ 170 void updateBalancerStatus(boolean status); 171 172 /** 173 * @return true if Master carries regions 174 * @deprecated since 2.4.0, will be removed in 3.0.0. 175 * @see <a href="https://issues.apache.org/jira/browse/HBASE-15549">HBASE-15549</a> 176 */ 177 @Deprecated 178 static boolean isTablesOnMaster(Configuration conf) { 179 return conf.getBoolean(TABLES_ON_MASTER, false); 180 } 181 182 /** 183 * @deprecated since 2.4.0, will be removed in 3.0.0. 184 * @see <a href="https://issues.apache.org/jira/browse/HBASE-15549">HBASE-15549</a> 185 */ 186 @Deprecated 187 static boolean isSystemTablesOnlyOnMaster(Configuration conf) { 188 return conf.getBoolean(SYSTEM_TABLES_ON_MASTER, false); 189 } 190 191 /** 192 * @deprecated since 2.4.0, will be removed in 3.0.0. 193 * @see <a href="https://issues.apache.org/jira/browse/HBASE-15549">HBASE-15549</a> 194 */ 195 @Deprecated 196 static boolean isMasterCanHostUserRegions(Configuration conf) { 197 return isTablesOnMaster(conf) && !isSystemTablesOnlyOnMaster(conf); 198 } 199}