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/**
*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.hadoop.hbase.master;
import edu.umd.cs.findbugs.annotations.NonNull;
import java.io.IOException;
import java.util.List;
import java.util.Map;
import org.apache.hadoop.conf.Configurable;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.ClusterMetrics;
import org.apache.hadoop.hbase.HBaseIOException;
import org.apache.hadoop.hbase.ServerName;
import org.apache.hadoop.hbase.Stoppable;
import org.apache.hadoop.hbase.TableName;
import org.apache.hadoop.hbase.client.RegionInfo;
import org.apache.hadoop.hbase.conf.ConfigurationObserver;
import org.apache.yetus.audience.InterfaceAudience;
/**
* Makes decisions about the placement and movement of Regions across
* RegionServers.
*
* Cluster-wide load balancing will occur only when there are no regions in
* transition and according to a fixed period of a time using {@link #balanceCluster(Map)}.
*
*
On cluster startup, bulk assignment can be used to determine
* locations for all Regions in a cluster.
*
*
This class produces plans for the
* {@link org.apache.hadoop.hbase.master.assignment.AssignmentManager}
* to execute.
*/
@InterfaceAudience.Private
public interface LoadBalancer extends Configurable, Stoppable, ConfigurationObserver {
/**
* Master can carry regions as of hbase-2.0.0.
* By default, it carries no tables.
* TODO: Add any | system as flags to indicate what it can do.
*
* @deprecated since 2.4.0, will be removed in 3.0.0.
* @see HBASE-15549
*/
@Deprecated
String TABLES_ON_MASTER = "hbase.balancer.tablesOnMaster";
/**
* Master carries system tables.
*
* @deprecated since 2.4.0, will be removed in 3.0.0.
* @see HBASE-15549
*/
@Deprecated
String SYSTEM_TABLES_ON_MASTER = "hbase.balancer.tablesOnMaster.systemTablesOnly";
// Used to signal to the caller that the region(s) cannot be assigned
// We deliberately use 'localhost' so the operation will fail fast
ServerName BOGUS_SERVER_NAME = ServerName.valueOf("localhost,1,1");
/**
* Set the current cluster status. This allows a LoadBalancer to map host name to a server
* @param st
*/
void setClusterMetrics(ClusterMetrics st);
/**
* Set the master service.
* @param masterServices
*/
void setMasterServices(MasterServices masterServices);
/**
* Perform the major balance operation for cluster, will invoke {@link #balanceTable} to do
* actual balance. Normally not need override this method, except SimpleLoadBalancer and
* RSGroupBasedLoadBalancer.
* @param loadOfAllTable region load of servers for all table
* @return a list of regions to be moved, including source and destination, or null if cluster is
* already balanced
*/
List balanceCluster(Map>> loadOfAllTable) throws IOException;
/**
* Perform the major balance operation for table, all class implement of {@link LoadBalancer}
* should override this method
* @param tableName the table to be balanced
* @param loadOfOneTable region load of servers for the specific one table
* @return List of plans
*/
List balanceTable(TableName tableName,
Map> loadOfOneTable);
/**
* Perform a Round Robin assignment of regions.
* @param regions
* @param servers
* @return Map of servername to regioninfos
*/
@NonNull
Map> roundRobinAssignment(List regions,
List servers) throws HBaseIOException;
/**
* Assign regions to the previously hosting region server
* @param regions
* @param servers
* @return List of plans
*/
@NonNull
Map> retainAssignment(Map regions,
List servers) throws HBaseIOException;
/**
* Get a random region server from the list
* @param regionInfo Region for which this selection is being done.
* @param servers
* @return Servername
*/
ServerName randomAssignment(
RegionInfo regionInfo, List servers
) throws HBaseIOException;
/**
* Initialize the load balancer. Must be called after setters.
* @throws HBaseIOException
*/
void initialize() throws HBaseIOException;
/**
* Marks the region as online at balancer.
* @param regionInfo
* @param sn
*/
void regionOnline(RegionInfo regionInfo, ServerName sn);
/**
* Marks the region as offline at balancer.
* @param regionInfo
*/
void regionOffline(RegionInfo regionInfo);
/*
* Notification that config has changed
* @param conf
*/
@Override
void onConfigurationChange(Configuration conf);
/**
* If balancer needs to do initialization after Master has started up, lets do that here.
*/
void postMasterStartupInitialize();
/*Updates balancer status tag reported to JMX*/
void updateBalancerStatus(boolean status);
/**
* @return true if Master carries regions
* @deprecated since 2.4.0, will be removed in 3.0.0.
* @see HBASE-15549
*/
@Deprecated
static boolean isTablesOnMaster(Configuration conf) {
return conf.getBoolean(TABLES_ON_MASTER, false);
}
/**
* @deprecated since 2.4.0, will be removed in 3.0.0.
* @see HBASE-15549
*/
@Deprecated
static boolean isSystemTablesOnlyOnMaster(Configuration conf) {
return conf.getBoolean(SYSTEM_TABLES_ON_MASTER, false);
}
/**
* @deprecated since 2.4.0, will be removed in 3.0.0.
* @see HBASE-15549
*/
@Deprecated
static boolean isMasterCanHostUserRegions(Configuration conf) {
return isTablesOnMaster(conf) && !isSystemTablesOnlyOnMaster(conf);
}
}