class ConsistentHashingShardAllocationStrategy extends ActorSystemDependentAllocationStrategy with ClusterShardAllocationMixin

akka.cluster.sharding.ShardCoordinator.ShardAllocationStrategy that is using consistent hashing. This can be useful when shards with the same shard id for different entity types should be best effort colocated to the same nodes.

When adding or removing nodes it will rebalance according to the new consistent hashing, but that means that only a few shards will be rebalanced and others remain on the same location.

A good explanation of Consistent Hashing: https://tom-e-white.com/2007/11/consistent-hashing.html

Create a new instance of this for each entity types, i.e. a ConsistentHashingShardAllocationStrategy instance must not be shared between different entity types.

Not intended for public inheritance/implementation

Annotations
@DoNotInherit()
Source
ConsistentHashingShardAllocationStrategy.scala
Linear Supertypes
ClusterShardAllocationMixin, ActorSystemDependentAllocationStrategy, ShardAllocationStrategy, NoSerializationVerificationNeeded, AnyRef, Any
Type Hierarchy
Ordering
  1. Alphabetic
  2. By Inheritance
Inherited
  1. ConsistentHashingShardAllocationStrategy
  2. ClusterShardAllocationMixin
  3. ActorSystemDependentAllocationStrategy
  4. ShardAllocationStrategy
  5. NoSerializationVerificationNeeded
  6. AnyRef
  7. Any
Implicitly
  1. by any2stringadd
  2. by StringFormat
  3. by Ensuring
  4. by ArrowAssoc
  1. Hide All
  2. Show All
Visibility
  1. Public
  2. Protected

Instance Constructors

  1. new ConsistentHashingShardAllocationStrategy(rebalanceLimit: Int)

Value Members

  1. def allocateShard(requester: ActorRef, shardId: ShardId, currentShardAllocations: Map[ActorRef, IndexedSeq[ShardId]]): Future[ActorRef]

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

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

    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

    Definition Classes
    ConsistentHashingShardAllocationStrategyShardAllocationStrategy
  2. def rebalance(currentShardAllocations: Map[ActorRef, IndexedSeq[ShardId]], rebalanceInProgress: Set[ShardId]): Future[Set[ShardId]]

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

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

    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

    Definition Classes
    ConsistentHashingShardAllocationStrategyShardAllocationStrategy
  3. def start(system: ActorSystem): Unit

    Called before any calls to allocate/rebalance.

    Called before any calls to allocate/rebalance. Do not block. If asynchronous actions are required they can be started here and delay the Futures returned by allocate/rebalance.

    Definition Classes
    ConsistentHashingShardAllocationStrategy → ActorSystemDependentAllocationStrategy