org.apache.druid.server.coordinator.balancer

Class RandomBalancerStrategy

java.lang.Object

org.apache.druid.server.coordinator.balancer.RandomBalancerStrategy

All Implemented Interfaces:

BalancerStrategy

public class RandomBalancerStrategy
extends Object
implements BalancerStrategy

A simple BalancerStrategy that

• assigns segments randomly amongst eligible servers
• performs no balancing

Constructor Summary

Constructors

Constructor and Description
RandomBalancerStrategy()

Method Summary

Modifier and Type	Method and Description
ServerHolder	findDestinationServerToMoveSegment(DataSegment segmentToMove, ServerHolder sourceServer, List<ServerHolder> serverHolders) Finds the best server from the list of destinationServers to load the segmentToMove, if it is moved from the sourceServer.
Iterator<ServerHolder>	findServersToDropSegment(DataSegment segmentToDrop, List<ServerHolder> serverHolders) Finds the best servers to drop the given segment.
Iterator<ServerHolder>	findServersToLoadSegment(DataSegment segmentToLoad, List<ServerHolder> serverHolders) Finds the best servers to load the given segment.
CoordinatorRunStats	getAndResetStats() Returns the stats collected by the strategy in the current run and resets the stats collector for the next run.

Methods inherited from class java.lang.Object

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

Constructor Detail

RandomBalancerStrategy

public RandomBalancerStrategy()

Method Detail

findServersToLoadSegment

public Iterator<ServerHolder> findServersToLoadSegment(DataSegment segmentToLoad,
                                                       List<ServerHolder> serverHolders)

Description copied from interface: BalancerStrategy

Finds the best servers to load the given segment. This method can be used both for placing the first copy of a segment in a tier or a replica of an already available segment.

Specified by:

findServersToLoadSegment in interface BalancerStrategy

Returns:

Iterator over the best servers (in order of preference) to load the segment.

findDestinationServerToMoveSegment

public ServerHolder findDestinationServerToMoveSegment(DataSegment segmentToMove,
                                                       ServerHolder sourceServer,
                                                       List<ServerHolder> serverHolders)

Description copied from interface: BalancerStrategy

Finds the best server from the list of destinationServers to load the segmentToMove, if it is moved from the sourceServer.

In order to avoid unnecessary moves when the segment is already optimally placed, include the sourceServer in the list of destinationServers.

Specified by:

findDestinationServerToMoveSegment in interface BalancerStrategy

Returns:

The server to move to, or null if the segment is already optimally placed.

findServersToDropSegment

public Iterator<ServerHolder> findServersToDropSegment(DataSegment segmentToDrop,
                                                       List<ServerHolder> serverHolders)

Description copied from interface: BalancerStrategy

Finds the best servers to drop the given segment.

Specified by:

findServersToDropSegment in interface BalancerStrategy

Returns:

Iterator over the servers (in order of preference) to drop the segment

getAndResetStats

public CoordinatorRunStats getAndResetStats()

Description copied from interface: BalancerStrategy

Returns the stats collected by the strategy in the current run and resets the stats collector for the next run.

Specified by:

getAndResetStats in interface BalancerStrategy