Package org.apache.accumulo.core.spi.balancer

Class SimpleLoadBalancer

java.lang.Object

org.apache.accumulo.core.spi.balancer.SimpleLoadBalancer

All Implemented Interfaces:

TabletBalancer

public class SimpleLoadBalancer
extends Object
implements TabletBalancer

A simple tablet balancer that attempts to spread tablets out evenly across all available tablet servers. The goal is to achieve the same number of tablets on each tablet server.

Initial assignments attempt to maintain locality by assigning tablets to their previous location if possible, but otherwise assignments are made in a random fashion across all available tablet servers.

This balancer replaces the deprecated org.apache.accumulo.server.master.balancer.DefaultLoadBalancer which will be removed in a future release. This balancer has the same functionality but uses the stable SPI which does not expose internal types on public methods.

Since:

2.1.0

Nested Class Summary

Nested classes/interfaces inherited from interface org.apache.accumulo.core.spi.balancer.TabletBalancer

TabletBalancer.AssignmentParameters, TabletBalancer.BalanceParameters

Field Summary

Fields

Modifier and Type	Field	Description
protected BalancerEnvironment	environment

Constructor Summary

Constructors

Constructor	Description
SimpleLoadBalancer()
SimpleLoadBalancer(TableId table)

Method Summary

Modifier and Type	Method	Description
long	balance(TabletBalancer.BalanceParameters params)	Ask the balancer if any migrations are necessary.
TabletServerId	getAssignment(SortedMap<TabletServerId,TServerStatus> locations, TabletServerId last)
void	getAssignments(TabletBalancer.AssignmentParameters params)	Assign tablets to tablet servers.
boolean	getMigrations(Map<TabletServerId,TServerStatus> current, List<TabletMigration> result)
protected List<TabletStatistics>	getOnlineTabletsForTable(TabletServerId tabletServerId, TableId tableId)
void	init(BalancerEnvironment balancerEnvironment)	Initialize the TabletBalancer.

Methods inherited from class java.lang.Object

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

Field Details

environment

protected BalancerEnvironment environment

Constructor Details

SimpleLoadBalancer

public SimpleLoadBalancer()

SimpleLoadBalancer

public SimpleLoadBalancer(TableId table)

Method Details

init

public void init(BalancerEnvironment balancerEnvironment)

Description copied from interface: TabletBalancer

Initialize the TabletBalancer. This gives the balancer the opportunity to read the configuration.

Specified by:

init in interface TabletBalancer

getAssignment

public TabletServerId getAssignment(SortedMap<TabletServerId,TServerStatus> locations,
 TabletServerId last)

getMigrations

public boolean getMigrations(Map<TabletServerId,TServerStatus> current,
 List<TabletMigration> result)

getOnlineTabletsForTable

protected List<TabletStatistics> getOnlineTabletsForTable(TabletServerId tabletServerId,
 TableId tableId)
                                                   throws AccumuloSecurityException,
AccumuloException

Throws:

AccumuloSecurityException

AccumuloException

getAssignments

public void getAssignments(TabletBalancer.AssignmentParameters params)

Description copied from interface: TabletBalancer

Assign tablets to tablet servers. This method is called whenever the manager finds tablets that are unassigned.

Specified by:

getAssignments in interface TabletBalancer

balance

public long balance(TabletBalancer.BalanceParameters params)

Description copied from interface: TabletBalancer

Ask the balancer if any migrations are necessary. If the balancer is going to self-abort due to some environmental constraint (e.g. it requires some minimum number of tservers, or a maximum number of outstanding migrations), it should issue a log message to alert operators. The message should be at WARN normally and at ERROR if the balancer knows that the problem can not self correct. It should not issue these messages more than once a minute. This method will not be called when there are unassigned tablets.

Specified by:

balance in interface TabletBalancer

Returns:

the time, in milliseconds, to wait before re-balancing.