org.apache.hadoop.hbase.master.balancer

Class FavoredNodeLoadBalancer

java.lang.Object

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

org.apache.hadoop.hbase.master.balancer.FavoredNodeLoadBalancer

All Implemented Interfaces:

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

@InterfaceAudience.LimitedPrivate(value="Configuration")
public class FavoredNodeLoadBalancer
extends BaseLoadBalancer

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.

Nested Class Summary

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.BaseLoadBalancer

metricsBalancer, services, slop

Constructor Summary

Constructors

Constructor and Description
FavoredNodeLoadBalancer()

Method Summary

Methods

Modifier and Type	Method and Description
List<RegionPlan>	balanceCluster(Map<ServerName,List<HRegionInfo>> clusterState) Perform the major balance operation
List<ServerName>	getFavoredNodes(HRegionInfo regionInfo)
ServerName	randomAssignment(HRegionInfo regionInfo, List<ServerName> servers) Used to assign a single region to a random server.
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	setConf(org.apache.hadoop.conf.Configuration conf)

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

getConf, immediateAssignment, initialize, isStopped, needsBalance, regionOffline, regionOnline, retainAssignment, setClusterStatus, setMasterServices, setSlop, stop

Methods inherited from class java.lang.Object

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

Constructor Detail

FavoredNodeLoadBalancer

public FavoredNodeLoadBalancer()

Method Detail

setConf

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

Specified by:

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

Overrides:

setConf in class BaseLoadBalancer

balanceCluster

public List<RegionPlan> balanceCluster(Map<ServerName,List<HRegionInfo>> clusterState)

Description copied from interface: LoadBalancer

Perform the major balance operation

Returns:

List of plans

roundRobinAssignment

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

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 null if no assignment is possible (ie. no regions or no servers)

randomAssignment

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

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.

Returns:

Servername

getFavoredNodes

public List<ServerName> getFavoredNodes(HRegionInfo regionInfo)