org.apache.druid.server.coordinator

Class RandomBalancerStrategy

java.lang.Object

org.apache.druid.server.coordinator.RandomBalancerStrategy

All Implemented Interfaces:

BalancerStrategy

public class RandomBalancerStrategy
extends Object
implements BalancerStrategy

Constructor Summary

Constructors

Constructor and Description
RandomBalancerStrategy()

Method Summary

Modifier and Type	Method and Description
void	emitStats(String tier, CoordinatorStats stats, List<ServerHolder> serverHolderList) Add balancing strategy stats during the 'balanceTier' operation of BalanceSegments to be included
ServerHolder	findNewSegmentHomeBalancer(DataSegment proposalSegment, List<ServerHolder> serverHolders) Find the best server to move a DataSegment to according the the balancing strategy.
ServerHolder	findNewSegmentHomeReplicator(DataSegment proposalSegment, List<ServerHolder> serverHolders) Find the best server on which to place a DataSegment replica according to the balancing strategy
BalancerSegmentHolder	pickSegmentToMove(List<ServerHolder> serverHolders, Set<String> broadcastDatasources) Pick the best segment to move from one of the supplied set of servers according to the balancing strategy.
Iterator<ServerHolder>	pickServersToDrop(DataSegment toDropSegment, NavigableSet<ServerHolder> serverHolders) Returns an iterator for a set of servers to drop from, ordered by preference of which server to drop from first for a given drop strategy.

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

findNewSegmentHomeReplicator

public ServerHolder findNewSegmentHomeReplicator(DataSegment proposalSegment,
                                                 List<ServerHolder> serverHolders)

Description copied from interface: BalancerStrategy

Find the best server on which to place a DataSegment replica according to the balancing strategy

Specified by:

findNewSegmentHomeReplicator in interface BalancerStrategy

Parameters:

proposalSegment - segment to replicate

serverHolders - servers to consider as replica holders

Returns:

The server to replicate to, or null if no suitable server is found

findNewSegmentHomeBalancer

public ServerHolder findNewSegmentHomeBalancer(DataSegment proposalSegment,
                                               List<ServerHolder> serverHolders)

Description copied from interface: BalancerStrategy

Find the best server to move a DataSegment to according the the balancing strategy.

Specified by:

findNewSegmentHomeBalancer in interface BalancerStrategy

Parameters:

proposalSegment - segment to move

serverHolders - servers to consider as move destinations

Returns:

The server to move to, or null if no move should be made or no server is suitable

pickSegmentToMove

public BalancerSegmentHolder pickSegmentToMove(List<ServerHolder> serverHolders,
                                               Set<String> broadcastDatasources)

Description copied from interface: BalancerStrategy

Pick the best segment to move from one of the supplied set of servers according to the balancing strategy.

Specified by:

pickSegmentToMove in interface BalancerStrategy

Parameters:

serverHolders - set of historicals to consider for moving segments

broadcastDatasources - Datasources that contain segments which were loaded via broadcast rules. Balancing strategies should avoid rebalancing segments for such datasources, since they should be loaded on all servers anyway. NOTE: this should really be handled on a per-segment basis, to properly support the interval or period-based broadcast rules. For simplicity of the initial implementation, only forever broadcast rules are supported.

Returns:

BalancerSegmentHolder containing segment to move and server it currently resides on, or null if there are no segments to pick from (i. e. all provided serverHolders are empty).

pickServersToDrop

public Iterator<ServerHolder> pickServersToDrop(DataSegment toDropSegment,
                                                NavigableSet<ServerHolder> serverHolders)

Description copied from interface: BalancerStrategy

Returns an iterator for a set of servers to drop from, ordered by preference of which server to drop from first for a given drop strategy. One or more segments may be dropped, depending on how much the segment is over-replicated.

Specified by:

pickServersToDrop in interface BalancerStrategy

Parameters:

toDropSegment - segment to drop from one or more servers

serverHolders - set of historicals to consider dropping from

Returns:

Iterator for set of historicals, ordered by drop preference

emitStats

public void emitStats(String tier,
                      CoordinatorStats stats,
                      List<ServerHolder> serverHolderList)

Description copied from interface: BalancerStrategy

Add balancing strategy stats during the 'balanceTier' operation of BalanceSegments to be included

Specified by:

emitStats in interface BalancerStrategy

Parameters:

tier - historical tier being balanced

stats - stats object to add balancing strategy stats to

serverHolderList - servers in tier being balanced