t

akka.cluster.sharding.ShardCoordinator

StartableAllocationStrategy

trait StartableAllocationStrategy extends ShardAllocationStrategy

Shard allocation strategy where start is called by the shard coordinator before any calls to rebalance or allocate shard. This can be used if there is any expensive initialization to be done that you do not want to to in the constructor as it will happen on every node rather than just the node that hosts the ShardCoordinator

Source
ShardCoordinator.scala
Linear Supertypes
ShardAllocationStrategy, NoSerializationVerificationNeeded, AnyRef, Any
Known Subclasses
ExternalShardAllocationStrategy
Type Hierarchy
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Inherited
  1. StartableAllocationStrategy
  2. ShardAllocationStrategy
  3. NoSerializationVerificationNeeded
  4. AnyRef
  5. Any
Implicitly
  1. by any2stringadd
  2. by StringFormat
  3. by Ensuring
  4. by ArrowAssoc
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Visibility
  1. Public
  2. Protected

Abstract Value Members

  1. abstract def allocateShard(requester: ActorRef, shardId: ShardId, currentShardAllocations: Map[, [ShardId]]): [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
    ShardAllocationStrategy
  2. abstract def rebalance(currentShardAllocations: Map[, [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
    ShardAllocationStrategy
  3. abstract def start(): 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.