org.elasticsearch.cluster.routing.allocation.decider

Class AwarenessAllocationDecider

java.lang.Object

org.elasticsearch.common.component.AbstractComponent

org.elasticsearch.cluster.routing.allocation.decider.AllocationDecider

org.elasticsearch.cluster.routing.allocation.decider.AwarenessAllocationDecider

public class AwarenessAllocationDecider
extends AllocationDecider

This AllocationDecider controls shard allocation based on awareness key-value pairs defined in the node configuration. Awareness explicitly controls where replicas should be allocated based on attributes like node or physical rack locations. Awareness attributes accept arbitrary configuration keys like a rack data-center identifier. For example the setting:

 cluster.routing.allocation.awareness.attributes: rack_id
 

will cause allocations to be distributed over different racks such that ideally at least one replicas of the all shard is available on the same rack. To enable allocation awareness in this example nodes should contain a value for the rack_id key like:

 node.rack_id:1
 

Awareness can also be used to prevent over-allocation in the case of node or even "zone" failure. For example in cloud-computing infrastructures like Amazone AWS a cluster might span over multiple "zones". Awareness can be used to distribute replicas to individual zones by setting:

 cluster.routing.allocation.awareness.attributes: zone
 

and forcing allocation to be aware of the following zone the data resides in:

 cluster.routing.allocation.awareness.force.zone.values: zone1,zone2
 

In contrast to regular awareness this setting will prevent over-allocation on zone1 even if zone2 fails partially or becomes entirely unavailable. Nodes that belong to a certain zone / group should be started with the zone id configured on the node-level settings like:

 node.zone: zone1
 

Field Summary

Fields

Modifier and Type	Field and Description
static String	CLUSTER_ROUTING_ALLOCATION_AWARENESS_ATTRIBUTES
static String	CLUSTER_ROUTING_ALLOCATION_AWARENESS_FORCE_GROUP
static String	NAME

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

deprecationLogger, logger, settings

Constructor Summary

Constructors

Constructor and Description
AwarenessAllocationDecider() Creates a new AwarenessAllocationDecider instance
AwarenessAllocationDecider(Settings settings) Creates a new AwarenessAllocationDecider instance from given settings
AwarenessAllocationDecider(Settings settings, NodeSettingsService nodeSettingsService)

Method Summary

Methods

Modifier and Type	Method and Description
String[]	awarenessAttributes() Get the attributes defined by this instance
Decision	canAllocate(ShardRouting shardRouting, RoutingNode node, RoutingAllocation allocation) Returns a Decision whether the given shard routing can be allocated on the given node.
Decision	canRemain(ShardRouting shardRouting, RoutingNode node, RoutingAllocation allocation) Returns a Decision whether the given shard routing can be remain on the given node.

Methods inherited from class org.elasticsearch.cluster.routing.allocation.decider.AllocationDecider

canAllocate, canAllocate, canAllocate, canRebalance, canRebalance

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

logDeprecatedSetting, logRemovedSetting, nodeName

Methods inherited from class java.lang.Object

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

Field Detail

NAME

public static final String NAME

See Also:

Constant Field Values

CLUSTER_ROUTING_ALLOCATION_AWARENESS_ATTRIBUTES

public static final String CLUSTER_ROUTING_ALLOCATION_AWARENESS_ATTRIBUTES

See Also:

Constant Field Values

CLUSTER_ROUTING_ALLOCATION_AWARENESS_FORCE_GROUP

public static final String CLUSTER_ROUTING_ALLOCATION_AWARENESS_FORCE_GROUP

See Also:

Constant Field Values

Constructor Detail

AwarenessAllocationDecider

public AwarenessAllocationDecider()

Creates a new AwarenessAllocationDecider instance

AwarenessAllocationDecider

public AwarenessAllocationDecider(Settings settings)

Creates a new AwarenessAllocationDecider instance from given settings

Parameters:

settings - Settings to use

AwarenessAllocationDecider

@Inject
public AwarenessAllocationDecider(Settings settings,
                                 NodeSettingsService nodeSettingsService)

Method Detail

awarenessAttributes

public String[] awarenessAttributes()

Get the attributes defined by this instance

Returns:

attributes defined by this instance

canAllocate

public Decision canAllocate(ShardRouting shardRouting,
                   RoutingNode node,
                   RoutingAllocation allocation)

Description copied from class: AllocationDecider

Returns a Decision whether the given shard routing can be allocated on the given node. The default is Decision.ALWAYS.

Overrides:

canAllocate in class AllocationDecider

canRemain

public Decision canRemain(ShardRouting shardRouting,
                 RoutingNode node,
                 RoutingAllocation allocation)

Description copied from class: AllocationDecider

Returns a Decision whether the given shard routing can be remain on the given node. The default is Decision.ALWAYS.

Overrides:

canRemain in class AllocationDecider