org.apache.hadoop.hbase.master

Interface LoadBalancer

All Superinterfaces:

org.apache.hadoop.conf.Configurable, ConfigurationObserver, Stoppable

All Known Implementing Classes:

BaseLoadBalancer, FavoredNodeLoadBalancer, FavoredStochasticBalancer, SimpleLoadBalancer, StochasticLoadBalancer

@InterfaceAudience.Private
public interface LoadBalancer
extends org.apache.hadoop.conf.Configurable, Stoppable, ConfigurationObserver

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 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 AssignmentManager to execute.

Field Summary

Fields

Modifier and Type	Field and Description
static ServerName	BOGUS_SERVER_NAME
static String	SYSTEM_TABLES_ON_MASTER Master carries system tables.
static String	TABLES_ON_MASTER Master can carry regions as of hbase-2.0.0.

Method Summary

Modifier and Type	Method and Description
List<RegionPlan>	balanceCluster(Map<ServerName,List<RegionInfo>> clusterState) Perform the major balance operation
List<RegionPlan>	balanceCluster(TableName tableName, Map<ServerName,List<RegionInfo>> clusterState) Perform the major balance operation
void	initialize() Initialize the load balancer.
static boolean	isMasterCanHostUserRegions(org.apache.hadoop.conf.Configuration conf)
static boolean	isSystemTablesOnlyOnMaster(org.apache.hadoop.conf.Configuration conf)
static boolean	isTablesOnMaster(org.apache.hadoop.conf.Configuration conf)
void	onConfigurationChange(org.apache.hadoop.conf.Configuration conf) This method would be called by the ConfigurationManager object when the Configuration object is reloaded from disk.
void	postMasterStartupInitialize() If balancer needs to do initialization after Master has started up, lets do that here.
ServerName	randomAssignment(RegionInfo regionInfo, List<ServerName> servers) Get a random region server from the list
void	regionOffline(RegionInfo regionInfo) Marks the region as offline at balancer.
void	regionOnline(RegionInfo regionInfo, ServerName sn) Marks the region as online at balancer.
Map<ServerName,List<RegionInfo>>	retainAssignment(Map<RegionInfo,ServerName> regions, List<ServerName> servers) Assign regions to the previously hosting region server
Map<ServerName,List<RegionInfo>>	roundRobinAssignment(List<RegionInfo> regions, List<ServerName> servers) Perform a Round Robin assignment of regions.
void	setClusterLoad(Map<TableName,Map<ServerName,List<RegionInfo>>> ClusterLoad) Pass RegionStates and allow balancer to set the current cluster load.
void	setClusterMetrics(ClusterMetrics st) Set the current cluster status.
void	setMasterServices(MasterServices masterServices) Set the master service.
void	updateBalancerStatus(boolean status)

Methods inherited from interface org.apache.hadoop.conf.Configurable

getConf, setConf

Methods inherited from interface org.apache.hadoop.hbase.Stoppable

isStopped, stop

Field Detail

TABLES_ON_MASTER

static final String TABLES_ON_MASTER

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.

See Also:

Constant Field Values

SYSTEM_TABLES_ON_MASTER

static final String SYSTEM_TABLES_ON_MASTER

Master carries system tables.

See Also:

Constant Field Values

BOGUS_SERVER_NAME

static final ServerName BOGUS_SERVER_NAME

Method Detail

setClusterMetrics

void setClusterMetrics(ClusterMetrics st)

Set the current cluster status. This allows a LoadBalancer to map host name to a server

Parameters:

st -

setClusterLoad

void setClusterLoad(Map<TableName,Map<ServerName,List<RegionInfo>>> ClusterLoad)

Pass RegionStates and allow balancer to set the current cluster load.

Parameters:

ClusterLoad -

setMasterServices

void setMasterServices(MasterServices masterServices)

Set the master service.

Parameters:

masterServices -

balanceCluster

List<RegionPlan> balanceCluster(TableName tableName,
                                Map<ServerName,List<RegionInfo>> clusterState)
                         throws HBaseIOException

Perform the major balance operation

Parameters:

tableName -

clusterState -

Returns:

List of plans

Throws:

HBaseIOException

balanceCluster

List<RegionPlan> balanceCluster(Map<ServerName,List<RegionInfo>> clusterState)
                         throws HBaseIOException

Perform the major balance operation

Parameters:

clusterState -

Returns:

List of plans

Throws:

HBaseIOException

roundRobinAssignment

Map<ServerName,List<RegionInfo>> roundRobinAssignment(List<RegionInfo> regions,
                                                      List<ServerName> servers)
                                               throws HBaseIOException

Perform a Round Robin assignment of regions.

Parameters:

regions -

servers -

Returns:

Map of servername to regioninfos

Throws:

HBaseIOException

retainAssignment

@Nullable
Map<ServerName,List<RegionInfo>> retainAssignment(Map<RegionInfo,ServerName> regions,
                                                            List<ServerName> servers)
                                                     throws HBaseIOException

Assign regions to the previously hosting region server

Parameters:

regions -

servers -

Returns:

List of plans

Throws:

HBaseIOException

randomAssignment

ServerName randomAssignment(RegionInfo regionInfo,
                            List<ServerName> servers)
                     throws HBaseIOException

Get a random region server from the list

Parameters:

regionInfo - Region for which this selection is being done.

servers -

Returns:

Servername

Throws:

HBaseIOException

initialize

void initialize()
         throws HBaseIOException

Initialize the load balancer. Must be called after setters.

Throws:

HBaseIOException

regionOnline

void regionOnline(RegionInfo regionInfo,
                  ServerName sn)

Marks the region as online at balancer.

Parameters:

regionInfo -

sn -

regionOffline

void regionOffline(RegionInfo regionInfo)

Marks the region as offline at balancer.

Parameters:

regionInfo -

onConfigurationChange

void onConfigurationChange(org.apache.hadoop.conf.Configuration conf)

Description copied from interface: ConfigurationObserver

This method would be called by the ConfigurationManager object when the Configuration object is reloaded from disk.

Specified by:

onConfigurationChange in interface ConfigurationObserver

postMasterStartupInitialize

void postMasterStartupInitialize()

If balancer needs to do initialization after Master has started up, lets do that here.

updateBalancerStatus

void updateBalancerStatus(boolean status)

isTablesOnMaster

static boolean isTablesOnMaster(org.apache.hadoop.conf.Configuration conf)

Returns:

true if Master carries regions

isSystemTablesOnlyOnMaster

static boolean isSystemTablesOnlyOnMaster(org.apache.hadoop.conf.Configuration conf)

isMasterCanHostUserRegions

static boolean isMasterCanHostUserRegions(org.apache.hadoop.conf.Configuration conf)