akka.cluster.sharding

Interface ShardCoordinator.ShardAllocationStrategy

All Superinterfaces:

NoSerializationVerificationNeeded

All Known Implementing Classes:

ShardCoordinator.AbstractShardAllocationStrategy, ShardCoordinator.LeastShardAllocationStrategy

Enclosing class:

ShardCoordinator

public static interface ShardCoordinator.ShardAllocationStrategy
extends NoSerializationVerificationNeeded

Interface of the pluggable shard allocation and rebalancing logic used by the ShardCoordinator.

Java implementations should extend ShardCoordinator.AbstractShardAllocationStrategy.

Method Summary

Modifier and Type	Method and Description
scala.concurrent.Future<ActorRef>	allocateShard(ActorRef requester, java.lang.String shardId, scala.collection.immutable.Map<ActorRef,scala.collection.immutable.IndexedSeq<java.lang.String>> currentShardAllocations) Invoked when the location of a new shard is to be decided.
scala.concurrent.Future<scala.collection.immutable.Set<java.lang.String>>	rebalance(scala.collection.immutable.Map<ActorRef,scala.collection.immutable.IndexedSeq<java.lang.String>> currentShardAllocations, scala.collection.immutable.Set<java.lang.String> rebalanceInProgress) Invoked periodically to decide which shards to rebalance to another location.

Method Detail

allocateShard

scala.concurrent.Future<ActorRef> allocateShard(ActorRef requester,
                                                java.lang.String shardId,
                                                scala.collection.immutable.Map<ActorRef,scala.collection.immutable.IndexedSeq<java.lang.String>> currentShardAllocations)

Invoked when the location of a new shard is to be decided.

Parameters:

requester - actor reference to the ShardRegion that requested the location of the shard, can be returned if preference should be given to the node where the shard was first accessed

shardId - the id of the shard to allocate

currentShardAllocations - all actor refs to ShardRegion and their current allocated shards, in the order they were allocated

Returns:

a Future of the actor ref of the ShardRegion that is to be responsible for the shard, must be one of the references included in the currentShardAllocations parameter

rebalance

scala.concurrent.Future<scala.collection.immutable.Set<java.lang.String>> rebalance(scala.collection.immutable.Map<ActorRef,scala.collection.immutable.IndexedSeq<java.lang.String>> currentShardAllocations,
                                                                                    scala.collection.immutable.Set<java.lang.String> rebalanceInProgress)

Invoked periodically to decide which shards to rebalance to another location.

Parameters:

currentShardAllocations - all actor refs to ShardRegion and their current allocated shards, in the order they were allocated

rebalanceInProgress - set of shards that are currently being rebalanced, i.e. you should not include these in the returned set

Returns:

a Future of the shards to be migrated, may be empty to skip rebalance in this round