org.elasticsearch.cluster.routing.allocation.allocator

Class EvenShardsCountAllocator

java.lang.Object

org.elasticsearch.common.component.AbstractComponent

org.elasticsearch.cluster.routing.allocation.allocator.EvenShardsCountAllocator

All Implemented Interfaces:

ShardsAllocator

public class EvenShardsCountAllocator
extends AbstractComponent
implements ShardsAllocator

A ShardsAllocator that tries to balance shards across nodes in the cluster such that each node holds approximatly the same number of shards. The allocations algorithm operates on a cluster ie. is index-agnostic. While the number of shards per node might be balanced across the cluster a single node can hold mulitple shards from a single index such that the shard of an index are not necessarily balanced across nodes. Yet, due to high-level decisions multiple instances of the same shard won't be allocated on the same node.

During re-balancing the allocator takes shards from the most busy nodes and tries to relocate the shards to the least busy node until the number of shards per node are equal for all nodes in the cluster or until no shards can be relocated anymore.

Field Summary

Fields inherited from class org.elasticsearch.common.component.AbstractComponent

componentSettings, logger, settings

Constructor Summary

Constructors

Constructor and Description
EvenShardsCountAllocator(Settings settings)

Method Summary

Modifier and Type	Method and Description
boolean	allocateUnassigned(RoutingAllocation allocation) Assign all unassigned shards to nodes
void	applyFailedShards(FailedRerouteAllocation allocation) Applies changes on failed nodes based on the implemented algorithm.
void	applyStartedShards(StartedRerouteAllocation allocation) Applies changes on started nodes based on the implemented algorithm.
boolean	move(MutableShardRouting shardRouting, RoutingNode node, RoutingAllocation allocation) Moves a shard from the given node to other node.
boolean	rebalance(RoutingAllocation allocation) Rebalancing number of shards on all nodes

Methods inherited from class org.elasticsearch.common.component.AbstractComponent

nodeName

Methods inherited from class java.lang.Object

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

Constructor Detail

EvenShardsCountAllocator

@Inject
public EvenShardsCountAllocator(Settings settings)

Method Detail

applyStartedShards

public void applyStartedShards(StartedRerouteAllocation allocation)

Description copied from interface: ShardsAllocator

Applies changes on started nodes based on the implemented algorithm. For example if a shard has changed to ShardRoutingState.STARTED from ShardRoutingState.RELOCATING this allocator might apply some cleanups on the node that used to hold the shard.

Specified by:

applyStartedShards in interface ShardsAllocator

Parameters:

allocation - all started shards

applyFailedShards

public void applyFailedShards(FailedRerouteAllocation allocation)

Description copied from interface: ShardsAllocator

Applies changes on failed nodes based on the implemented algorithm.

Specified by:

applyFailedShards in interface ShardsAllocator

Parameters:

allocation - all failed shards

allocateUnassigned

public boolean allocateUnassigned(RoutingAllocation allocation)

Description copied from interface: ShardsAllocator

Assign all unassigned shards to nodes

Specified by:

allocateUnassigned in interface ShardsAllocator

Parameters:

allocation - current node allocation

Returns:

true if the allocation has changed, otherwise false

rebalance

public boolean rebalance(RoutingAllocation allocation)

Description copied from interface: ShardsAllocator

Rebalancing number of shards on all nodes

Specified by:

rebalance in interface ShardsAllocator

Parameters:

allocation - current node allocation

Returns:

true if the allocation has changed, otherwise false

move

public boolean move(MutableShardRouting shardRouting,
                    RoutingNode node,
                    RoutingAllocation allocation)

Description copied from interface: ShardsAllocator

Moves a shard from the given node to other node.

Specified by:

move in interface ShardsAllocator

Parameters:

shardRouting - the shard to move

node - A node containing the shard

allocation - current node allocation

Returns:

true if the allocation has changed, otherwise false