Package org.elasticsearch.cluster.routing.allocation.decider

Class AwarenessAllocationDecider

java.lang.Object

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.attr.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 Amazon 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	Description
static Setting<List<String>>	CLUSTER_ROUTING_ALLOCATION_AWARENESS_ATTRIBUTE_SETTING
static Setting<Settings>	CLUSTER_ROUTING_ALLOCATION_AWARENESS_FORCE_GROUP_SETTING
static String	NAME

Constructor Summary

Constructors

Constructor	Description
AwarenessAllocationDecider(Settings settings, ClusterSettings clusterSettings)

Method Summary

Modifier and Type	Method	Description
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, canForceAllocatePrimary, canRebalance, canRebalance, shouldAutoExpandToNode

Methods inherited from class java.lang.Object

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

Field Details

NAME

public static final String NAME

See Also:

Constant Field Values

CLUSTER_ROUTING_ALLOCATION_AWARENESS_ATTRIBUTE_SETTING

public static final Setting<List<String>> CLUSTER_ROUTING_ALLOCATION_AWARENESS_ATTRIBUTE_SETTING

CLUSTER_ROUTING_ALLOCATION_AWARENESS_FORCE_GROUP_SETTING

public static final Setting<Settings> CLUSTER_ROUTING_ALLOCATION_AWARENESS_FORCE_GROUP_SETTING

Constructor Details

AwarenessAllocationDecider

public AwarenessAllocationDecider(Settings settings,
 ClusterSettings clusterSettings)

Method Details

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