org.apache.hadoop.hbase.master.balancer

Class FavoredStochasticBalancer

java.lang.Object

org.apache.hadoop.hbase.master.balancer.BaseLoadBalancer

org.apache.hadoop.hbase.master.balancer.StochasticLoadBalancer

org.apache.hadoop.hbase.master.balancer.FavoredStochasticBalancer

All Implemented Interfaces:

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

@InterfaceAudience.Private
public class FavoredStochasticBalancer
extends StochasticLoadBalancer
implements FavoredNodesPromoter

An implementation of the LoadBalancer that assigns favored nodes for each region. There is a Primary RegionServer that hosts the region, and then there is Secondary and Tertiary RegionServers. Currently, the favored nodes information is used in creating HDFS files - the Primary RegionServer passes the primary, secondary, tertiary node addresses as hints to the DistributedFileSystem API for creating files on the filesystem. These nodes are treated as hints by the HDFS to place the blocks of the file. This alleviates the problem to do with reading from remote nodes (since we can make the Secondary RegionServer as the new Primary RegionServer) after a region is recovered. This should help provide consistent read latencies for the regions even when their primary region servers die. This provides two CandidateGenerator

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.hadoop.hbase.master.balancer.StochasticLoadBalancer

StochasticLoadBalancer.CostFunction, StochasticLoadBalancer.GeneratorType

Nested classes/interfaces inherited from class org.apache.hadoop.hbase.master.balancer.BaseLoadBalancer

BaseLoadBalancer.Cluster

Field Summary

Fields inherited from class org.apache.hadoop.hbase.master.balancer.StochasticLoadBalancer

candidateGenerators, COST_EPSILON, COST_FUNCTIONS_COST_FUNCTIONS_KEY, KEEP_REGION_LOADS, MAX_RUNNING_TIME_KEY, MAX_STEPS_KEY, MIN_COST_NEED_BALANCE_KEY, RANDOM, RUN_MAX_STEPS_KEY, STEPS_PER_REGION_KEY

Fields inherited from class org.apache.hadoop.hbase.master.balancer.BaseLoadBalancer

BALANCER_DECISION_BUFFER_ENABLED, BALANCER_REJECTION_BUFFER_ENABLED, clusterStatus, config, DEFAULT_BALANCER_DECISION_BUFFER_ENABLED, DEFAULT_BALANCER_REJECTION_BUFFER_ENABLED, isByTable, masterServerName, metricsBalancer, MIN_SERVER_BALANCE, onlySystemTablesOnMaster, overallSlop, rackManager, regionFinder, services, slop, useRegionFinder

Fields inherited from interface org.apache.hadoop.hbase.favored.FavoredNodesPromoter

FAVORED_ALWAYS_ASSIGN_REGIONS

Fields inherited from interface org.apache.hadoop.hbase.master.LoadBalancer

BOGUS_SERVER_NAME, SYSTEM_TABLES_ON_MASTER, TABLES_ON_MASTER

Constructor Summary

Constructors

Constructor and Description
FavoredStochasticBalancer()

Method Summary

Modifier and Type	Method and Description
List<RegionPlan>	balanceTable(TableName tableName, Map<ServerName,List<RegionInfo>> loadOfOneTable) Given the cluster state this will try and approach an optimal balance.
protected void	configureGenerators()
void	generateFavoredNodesForDaughter(List<ServerName> servers, RegionInfo parent, RegionInfo regionA, RegionInfo regionB)
void	generateFavoredNodesForMergedRegion(RegionInfo merged, RegionInfo[] mergeParents)
List<ServerName>	getFavoredNodes(RegionInfo regionInfo)
protected org.apache.hadoop.hbase.master.balancer.CandidateGenerator	getRandomGenerator() Returns any candidate generator in random
void	initialize() Initialize the load balancer.
ServerName	randomAssignment(RegionInfo regionInfo, List<ServerName> servers) Used to assign a single region to a random server.
Map<ServerName,List<RegionInfo>>	retainAssignment(Map<RegionInfo,ServerName> regions, List<ServerName> servers) Generates a bulk assignment startup plan, attempting to reuse the existing assignment information from META, but adjusting for the specified list of available/online servers available for assignment.
Map<ServerName,List<RegionInfo>>	roundRobinAssignment(List<RegionInfo> regions, List<ServerName> servers) Generates a bulk assignment plan to be used on cluster startup using a simple round-robin assignment.
void	setMasterServices(MasterServices masterServices) Set the master service.

Methods inherited from class org.apache.hadoop.hbase.master.balancer.StochasticLoadBalancer

areSomeRegionReplicasColocated, composeAttributeName, getCandidateGenerators, needsBalance, onConfigurationChange, setCandidateGenerators, setClusterMetrics, setConf, setSlop, updateMetricsSize

Methods inherited from class org.apache.hadoop.hbase.master.balancer.BaseLoadBalancer

assignMasterSystemRegions, balanceCluster, balanceMasterRegions, createCluster, getConf, getRegionAssignmentsByServer, idleRegionServerExist, isStopped, postMasterStartupInitialize, regionOffline, regionOnline, setRackManager, shouldBeOnMaster, stop, updateBalancerStatus

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface org.apache.hadoop.hbase.master.LoadBalancer

isMasterCanHostUserRegions, isSystemTablesOnlyOnMaster, isTablesOnMaster

Constructor Detail

FavoredStochasticBalancer

public FavoredStochasticBalancer()

Method Detail

initialize

public void initialize()
                throws HBaseIOException

Description copied from interface: LoadBalancer

Initialize the load balancer. Must be called after setters.

Specified by:

initialize in interface LoadBalancer

Overrides:

initialize in class BaseLoadBalancer

Throws:

HBaseIOException

configureGenerators

protected void configureGenerators()

getRandomGenerator

protected org.apache.hadoop.hbase.master.balancer.CandidateGenerator getRandomGenerator()

Returns any candidate generator in random

Overrides:

getRandomGenerator in class StochasticLoadBalancer

setMasterServices

public void setMasterServices(MasterServices masterServices)

Description copied from interface: LoadBalancer

Set the master service.

Specified by:

setMasterServices in interface LoadBalancer

Overrides:

setMasterServices in class BaseLoadBalancer

roundRobinAssignment

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

Description copied from class: BaseLoadBalancer

Generates a bulk assignment plan to be used on cluster startup using a simple round-robin assignment.

Takes a list of all the regions and all the servers in the cluster and returns a map of each server to the regions that it should be assigned.

Currently implemented as a round-robin assignment. Same invariant as load balancing, all servers holding floor(avg) or ceiling(avg). TODO: Use block locations from HDFS to place regions with their blocks

Specified by:

roundRobinAssignment in interface LoadBalancer

Overrides:

roundRobinAssignment in class BaseLoadBalancer

Parameters:

regions - all regions

servers - all servers

Returns:

map of server to the regions it should take, or emptyMap if no assignment is possible (ie. no servers)

Throws:

HBaseIOException

randomAssignment

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

Description copied from class: BaseLoadBalancer

Used to assign a single region to a random server.

Specified by:

randomAssignment in interface LoadBalancer

Overrides:

randomAssignment in class BaseLoadBalancer

Parameters:

regionInfo - Region for which this selection is being done.

Throws:

HBaseIOException

retainAssignment

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

Description copied from class: BaseLoadBalancer

Generates a bulk assignment startup plan, attempting to reuse the existing assignment information from META, but adjusting for the specified list of available/online servers available for assignment.

Takes a map of all regions to their existing assignment from META. Also takes a list of online servers for regions to be assigned to. Attempts to retain all assignment, so in some instances initial assignment will not be completely balanced.

Any leftover regions without an existing server to be assigned to will be assigned randomly to available servers.

Specified by:

retainAssignment in interface LoadBalancer

Overrides:

retainAssignment in class BaseLoadBalancer

Parameters:

regions - regions and existing assignment from meta

servers - available servers

Returns:

map of servers and regions to be assigned to them, or emptyMap if no assignment is possible (ie. no servers)

Throws:

HBaseIOException

getFavoredNodes

public List<ServerName> getFavoredNodes(RegionInfo regionInfo)

generateFavoredNodesForDaughter

public void generateFavoredNodesForDaughter(List<ServerName> servers,
                                            RegionInfo parent,
                                            RegionInfo regionA,
                                            RegionInfo regionB)
                                     throws IOException

Specified by:

generateFavoredNodesForDaughter in interface FavoredNodesPromoter

Throws:

IOException

generateFavoredNodesForMergedRegion

public void generateFavoredNodesForMergedRegion(RegionInfo merged,
                                                RegionInfo[] mergeParents)
                                         throws IOException

Specified by:

generateFavoredNodesForMergedRegion in interface FavoredNodesPromoter

Throws:

IOException

balanceTable

public List<RegionPlan> balanceTable(TableName tableName,
                                     Map<ServerName,List<RegionInfo>> loadOfOneTable)

Description copied from class: StochasticLoadBalancer

Given the cluster state this will try and approach an optimal balance. This should always approach the optimal state given enough steps.

Specified by:

balanceTable in interface LoadBalancer

Overrides:

balanceTable in class StochasticLoadBalancer

Parameters:

tableName - the table to be balanced

loadOfOneTable - region load of servers for the specific one table

Returns:

List of plans