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

java.lang.Object
  org.apache.hadoop.hbase.master.balancer.BaseLoadBalancer

All Implemented Interfaces:

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

Direct Known Subclasses:

FavoredNodeLoadBalancer, SimpleLoadBalancer, StochasticLoadBalancer

public abstract class BaseLoadBalancer
extends Object
implements LoadBalancer

The base class for load balancers. It provides the the functions used to by AssignmentManager to assign regions in the edge cases. It doesn't provide an implementation of the actual balancing algorithm.

Nested Class Summary

protected static class

BaseLoadBalancer.Cluster An efficient array based implementation similar to ClusterState for keeping the status of the cluster in terms of region assignment and distribution.

Field Summary

protected MetricsBalancer	metricsBalancer
protected MasterServices	services
protected float	slop

Constructor Summary

BaseLoadBalancer()

Method Summary

org.apache.hadoop.conf.Configuration	getConf()
Map<HRegionInfo,ServerName>	immediateAssignment(List<HRegionInfo> regions, List<ServerName> servers) Generates an immediate assignment plan to be used by a new master for regions in transition that do not have an already known destination.
void	initialize() Initialize the load balancer.
boolean	isStopped()
protected boolean	needsBalance(ClusterLoadState cs)
ServerName	randomAssignment(HRegionInfo regionInfo, List<ServerName> servers) Used to assign a single region to a random server.
void	regionOffline(HRegionInfo regionInfo) Marks the region as offline at balancer.
void	regionOnline(HRegionInfo regionInfo, ServerName sn) Marks the region as online at balancer.
Map<ServerName,List<HRegionInfo>>	retainAssignment(Map<HRegionInfo,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<HRegionInfo>>	roundRobinAssignment(List<HRegionInfo> regions, List<ServerName> servers) Generates a bulk assignment plan to be used on cluster startup using a simple round-robin assignment.
void	setClusterStatus(ClusterStatus st) Set the current cluster status.
void	setConf(org.apache.hadoop.conf.Configuration conf)
void	setMasterServices(MasterServices masterServices) Set the master service.
protected void	setSlop(org.apache.hadoop.conf.Configuration conf)
void	stop(String why)

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

balanceCluster

Field Detail

slop

protected float slop

metricsBalancer

protected final MetricsBalancer metricsBalancer

services

protected MasterServices services

Constructor Detail

BaseLoadBalancer

public BaseLoadBalancer()

Method Detail

setConf

public void setConf(org.apache.hadoop.conf.Configuration conf)

Specified by:

setConf in interface org.apache.hadoop.conf.Configurable

setSlop

protected void setSlop(org.apache.hadoop.conf.Configuration conf)

getConf

public org.apache.hadoop.conf.Configuration getConf()

Specified by:

getConf in interface org.apache.hadoop.conf.Configurable

setClusterStatus

public void setClusterStatus(ClusterStatus st)

Description copied from interface: LoadBalancer

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

Specified by:

setClusterStatus in interface LoadBalancer

setMasterServices

public void setMasterServices(MasterServices masterServices)

Description copied from interface: LoadBalancer

Set the master service.

Specified by:

setMasterServices in interface LoadBalancer

needsBalance

protected boolean needsBalance(ClusterLoadState cs)

roundRobinAssignment

public Map<ServerName,List<HRegionInfo>> roundRobinAssignment(List<HRegionInfo> regions,
                                                              List<ServerName> servers)

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

Parameters:

regions - all regions

servers - all servers

Returns:

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

immediateAssignment

public Map<HRegionInfo,ServerName> immediateAssignment(List<HRegionInfo> regions,
                                                       List<ServerName> servers)

Generates an immediate assignment plan to be used by a new master for regions in transition that do not have an already known destination. Takes a list of regions that need immediate assignment and a list of all available servers. Returns a map of regions to the server they should be assigned to. This method will return quickly and does not do any intelligent balancing. The goal is to make a fast decision not the best decision possible. Currently this is random.

Specified by:

immediateAssignment in interface LoadBalancer

Parameters:

regions -

servers -

Returns:

map of regions to the server it should be assigned to

randomAssignment

public ServerName randomAssignment(HRegionInfo regionInfo,
                                   List<ServerName> servers)

Used to assign a single region to a random server.

Specified by:

randomAssignment in interface LoadBalancer

Parameters:

regionInfo - Region for which this selection is being done.

Returns:

Servername

retainAssignment

public Map<ServerName,List<HRegionInfo>> retainAssignment(Map<HRegionInfo,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.

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

Parameters:

regions - regions and existing assignment from meta

servers - available servers

Returns:

map of servers and regions to be assigned to them

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

Throws:

HBaseIOException

regionOnline

public void regionOnline(HRegionInfo regionInfo,
                         ServerName sn)

Description copied from interface: LoadBalancer

Marks the region as online at balancer.

Specified by:

regionOnline in interface LoadBalancer

regionOffline

public void regionOffline(HRegionInfo regionInfo)

Description copied from interface: LoadBalancer

Marks the region as offline at balancer.

Specified by:

regionOffline in interface LoadBalancer

isStopped

public boolean isStopped()

Specified by:

isStopped in interface Stoppable

stop

public void stop(String why)

Specified by:

stop in interface Stoppable