trait ShardAllocationStrategy extends NoSerializationVerificationNeeded
Interface of the pluggable shard allocation and rebalancing logic used by the ShardCoordinator.
Java implementations should extend AbstractShardAllocationStrategy.
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- ShardCoordinator.scala
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abstract
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 thecurrentShardAllocations
parameter
-
abstract
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