StochasticLoadBalancer (Apache HBase

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

所有已实现的接口:

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

直接已知子类:

FavoredStochasticBalancer
```
@InterfaceAudience.LimitedPrivate(value="Configuration")
public class StochasticLoadBalancer
extends BaseLoadBalancer
```
This is a best effort load balancer. Given a Cost function F(C) => x It will randomly try and mutate the cluster to Cprime. If F(Cprime) < F(C) then the new cluster state becomes the plan. It includes costs functions to compute the cost of:
- Region Load
- Table Load
- Data Locality
- Memstore Sizes
- Storefile Sizes
Every cost function returns a number between 0 and 1 inclusive; where 0 is the lowest cost best solution, and 1 is the highest possible cost and the worst solution. The computed costs are scaled by their respective multipliers:
- hbase.master.balancer.stochastic.regionLoadCost
- hbase.master.balancer.stochastic.moveCost
- hbase.master.balancer.stochastic.tableLoadCost
- hbase.master.balancer.stochastic.localityCost
- hbase.master.balancer.stochastic.memstoreSizeCost
- hbase.master.balancer.stochastic.storefileSizeCost
In addition to the above configurations, the balancer can be tuned by the following configuration values:
- hbase.master.balancer.stochastic.maxMoveRegions which controls what the max number of regions that can be moved in a single invocation of this balancer.
- hbase.master.balancer.stochastic.stepsPerRegion is the coefficient by which the number of regions is multiplied to try and get the number of times the balancer will mutate all servers.
- hbase.master.balancer.stochastic.maxSteps which controls the maximum number of times that the balancer will try and mutate all the servers. The balancer will use the minimum of this value and the above computation.
This balancer is best used with hbase.master.loadbalance.bytable set to false so that the balancer gets the full picture of all loads on the cluster.

嵌套类概要
- 从类继承的嵌套类/接口 org.apache.hadoop.hbase.master.balancer.BaseLoadBalancer
  BaseLoadBalancer.Cluster

字段概要

字段
限定符和类型	字段和说明
`protected static String`	`KEEP_REGION_LOADS`
`protected static String`	`MAX_RUNNING_TIME_KEY`
`protected static String`	`MAX_STEPS_KEY`
`protected static String`	`MIN_COST_NEED_BALANCE_KEY`
`protected static Random`	`RANDOM`
`protected static String`	`RUN_MAX_STEPS_KEY`
`protected static String`	`STEPS_PER_REGION_KEY`

从类继承的字段 org.apache.hadoop.hbase.master.balancer.BaseLoadBalancer
clusterStatus, config, maintenanceMode, masterServerName, metricsBalancer, MIN_SERVER_BALANCE, onlySystemTablesOnMaster, overallSlop, rackManager, regionFinder, services, slop, useRegionFinder

从接口继承的字段 org.apache.hadoop.hbase.master.LoadBalancer
BOGUS_SERVER_NAME, SYSTEM_TABLES_ON_MASTER, TABLES_ON_MASTER

构造器概要

构造器
构造器和说明

StochasticLoadBalancer()
The constructor that pass a MetricsStochasticBalancer to BaseLoadBalancer to replace its default MetricsBalancer

构造器
构造器和说明
`StochasticLoadBalancer()` The constructor that pass a MetricsStochasticBalancer to BaseLoadBalancer to replace its default MetricsBalancer

方法概要

所有方法静态方法实例方法具体方法
限定符和类型	方法和说明
`protected boolean`	`areSomeRegionReplicasColocated(BaseLoadBalancer.Cluster c)` Subclasses should implement this to return true if the cluster has nodes that hosts multiple replicas for the same region, or, if there are multiple racks and the same rack hosts replicas of the same region
`List<RegionPlan>`	`balanceCluster(Map<ServerName,List<RegionInfo>> clusterState)` Given the cluster state this will try and approach an optimal balance.
`List<RegionPlan>`	`balanceCluster(TableName tableName, Map<ServerName,List<RegionInfo>> clusterState)` Perform the major balance operation
`static String`	`composeAttributeName(String tableName, String costFunctionName)` A helper function to compose the attribute name from tablename and costfunction name
`protected double`	`computeCost(BaseLoadBalancer.Cluster cluster, double previousCost)` This is the main cost function.
`String[]`	`getCostFunctionNames()` Get the names of the cost functions
`protected void`	`initCosts(BaseLoadBalancer.Cluster cluster)`
`protected boolean`	`needsBalance(BaseLoadBalancer.Cluster cluster)`
`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.
`protected void`	`setCandidateGenerators(List<org.apache.hadoop.hbase.master.balancer.StochasticLoadBalancer.CandidateGenerator> customCandidateGenerators)`
`void`	`setClusterMetrics(ClusterMetrics 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)`
`protected void`	`updateCostsWithAction(BaseLoadBalancer.Cluster cluster, BaseLoadBalancer.Cluster.Action action)`
`void`	`updateMetricsSize(int size)` Update the number of metrics that are reported to JMX

从类继承的方法 org.apache.hadoop.hbase.master.balancer.BaseLoadBalancer
assignMasterSystemRegions, balanceMasterRegions, createCluster, getConf, getRegionAssignmentsByServer, initialize, isStopped, postMasterStartupInitialize, randomAssignment, regionOffline, regionOnline, retainAssignment, roundRobinAssignment, setClusterLoad, setRackManager, shouldBeOnMaster, stop, updateBalancerStatus

从类继承的方法 java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

从接口继承的方法 org.apache.hadoop.hbase.master.LoadBalancer
isMasterCanHostUserRegions, isSystemTablesOnlyOnMaster, isTablesOnMaster

- 字段详细资料
  - STEPS_PER_REGION_KEY
```
protected static final String STEPS_PER_REGION_KEY
```
    另请参阅:
    
    常量字段值
  - MAX_STEPS_KEY
```
protected static final String MAX_STEPS_KEY
```
    另请参阅:
    
    常量字段值
  - RUN_MAX_STEPS_KEY
```
protected static final String RUN_MAX_STEPS_KEY
```
    另请参阅:
    
    常量字段值
  - MAX_RUNNING_TIME_KEY
```
protected static final String MAX_RUNNING_TIME_KEY
```
    另请参阅:
    
    常量字段值
  - KEEP_REGION_LOADS
```
protected static final String KEEP_REGION_LOADS
```
    另请参阅:
    
    常量字段值
  - MIN_COST_NEED_BALANCE_KEY
```
protected static final String MIN_COST_NEED_BALANCE_KEY
```
    另请参阅:
    
    常量字段值
  - RANDOM
```
protected static final Random RANDOM
```
- 构造器详细资料
  - StochasticLoadBalancer
```
public StochasticLoadBalancer()
```
    The constructor that pass a MetricsStochasticBalancer to BaseLoadBalancer to replace its default MetricsBalancer
- 方法详细资料
  - onConfigurationChange
```
public void onConfigurationChange(org.apache.hadoop.conf.Configuration conf)
```
    从接口复制的说明: ConfigurationObserver
    
    This method would be called by the ConfigurationManager object when the Configuration object is reloaded from disk.
    
    指定者:
    
    onConfigurationChange 在接口中 ConfigurationObserver
    
    指定者:
    
    onConfigurationChange 在接口中 LoadBalancer
    
    覆盖:
    
    onConfigurationChange 在类中 BaseLoadBalancer
  - setConf
```
public void setConf(org.apache.hadoop.conf.Configuration conf)
```
    指定者:
    
    setConf 在接口中 org.apache.hadoop.conf.Configurable
    
    覆盖:
    
    setConf 在类中 BaseLoadBalancer
  - setCandidateGenerators
```
protected void setCandidateGenerators(List<org.apache.hadoop.hbase.master.balancer.StochasticLoadBalancer.CandidateGenerator> customCandidateGenerators)
```
  - setSlop
```
protected void setSlop(org.apache.hadoop.conf.Configuration conf)
```
    覆盖:
    
    setSlop 在类中 BaseLoadBalancer
  - setClusterMetrics
```
public void setClusterMetrics(ClusterMetrics st)
```
    从接口复制的说明: LoadBalancer
    
    Set the current cluster status. This allows a LoadBalancer to map host name to a server
    
    指定者:
    
    setClusterMetrics 在接口中 LoadBalancer
    
    覆盖:
    
    setClusterMetrics 在类中 BaseLoadBalancer
  - updateMetricsSize
```
public void updateMetricsSize(int size)
```
    Update the number of metrics that are reported to JMX
  - setMasterServices
```
public void setMasterServices(MasterServices masterServices)
```
    从接口复制的说明: LoadBalancer
    
    Set the master service.
    
    指定者:
    
    setMasterServices 在接口中 LoadBalancer
    
    覆盖:
    
    setMasterServices 在类中 BaseLoadBalancer
  - areSomeRegionReplicasColocated
```
protected boolean areSomeRegionReplicasColocated(BaseLoadBalancer.Cluster c)
```
    从类复制的说明: BaseLoadBalancer
    
    Subclasses should implement this to return true if the cluster has nodes that hosts multiple replicas for the same region, or, if there are multiple racks and the same rack hosts replicas of the same region
    
    覆盖:
    
    areSomeRegionReplicasColocated 在类中 BaseLoadBalancer
    
    参数:
    
    c - Cluster information
    
    返回:
    
    whether region replicas are currently co-located
  - needsBalance
```
protected boolean needsBalance(BaseLoadBalancer.Cluster cluster)
```
    覆盖:
    
    needsBalance 在类中 BaseLoadBalancer
  - balanceCluster
```
public List<RegionPlan> balanceCluster(TableName tableName,
                                       Map<ServerName,List<RegionInfo>> clusterState)
```
    从接口复制的说明: LoadBalancer
    
    Perform the major balance operation
    
    返回:
    
    List of plans
  - balanceCluster
```
public List<RegionPlan> balanceCluster(Map<ServerName,List<RegionInfo>> clusterState)
```
    Given the cluster state this will try and approach an optimal balance. This should always approach the optimal state given enough steps.
    
    返回:
    
    List of plans
  - initCosts
```
protected void initCosts(BaseLoadBalancer.Cluster cluster)
```
  - updateCostsWithAction
```
protected void updateCostsWithAction(BaseLoadBalancer.Cluster cluster,
                                     BaseLoadBalancer.Cluster.Action action)
```
  - getCostFunctionNames
```
public String[] getCostFunctionNames()
```
    Get the names of the cost functions
  - computeCost
```
protected double computeCost(BaseLoadBalancer.Cluster cluster,
                             double previousCost)
```
    This is the main cost function. It will compute a cost associated with a proposed cluster state. All different costs will be combined with their multipliers to produce a double cost.
    
    参数:
    
    cluster - The state of the cluster
    
    previousCost - the previous cost. This is used as an early out.
    
    返回:
    
    a double of a cost associated with the proposed cluster state. This cost is an aggregate of all individual cost functions.
  - composeAttributeName
```
public static String composeAttributeName(String tableName,
                                          String costFunctionName)
```
    A helper function to compose the attribute name from tablename and costfunction name

类 StochasticLoadBalancer

嵌套类概要

从类继承的嵌套类/接口 org.apache.hadoop.hbase.master.balancer.BaseLoadBalancer

字段概要

从类继承的字段 org.apache.hadoop.hbase.master.balancer.BaseLoadBalancer

从接口继承的字段 org.apache.hadoop.hbase.master.LoadBalancer

构造器概要

方法概要

从类继承的方法 org.apache.hadoop.hbase.master.balancer.BaseLoadBalancer

从类继承的方法 java.lang.Object

从接口继承的方法 org.apache.hadoop.hbase.master.LoadBalancer

字段详细资料

STEPS_PER_REGION_KEY

MAX_STEPS_KEY

RUN_MAX_STEPS_KEY

MAX_RUNNING_TIME_KEY

KEEP_REGION_LOADS

MIN_COST_NEED_BALANCE_KEY

RANDOM

构造器详细资料

StochasticLoadBalancer

方法详细资料

onConfigurationChange

setConf

setCandidateGenerators

setSlop

setClusterMetrics

updateMetricsSize

setMasterServices

areSomeRegionReplicasColocated

needsBalance

balanceCluster

balanceCluster

initCosts

updateCostsWithAction

getCostFunctionNames

computeCost

composeAttributeName