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
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- ConsistentHashingShardAllocationStrategy.scala
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- This member is added by an implicit conversion from ConsistentHashingShardAllocationStrategy toany2stringadd[ConsistentHashingShardAllocationStrategy] performed by method any2stringadd in scala.Predef.
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- def ->[B](y: B): (ConsistentHashingShardAllocationStrategy, B)
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- This member is added by an implicit conversion from ConsistentHashingShardAllocationStrategy toArrowAssoc[ConsistentHashingShardAllocationStrategy] performed by method ArrowAssoc in scala.Predef.
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- 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
ShardRegionand their current allocated shards, in the order they were allocated- returns
a
Futureof the actor ref of the ShardRegion that is to be responsible for the shard, must be one of the references included in thecurrentShardAllocationsparameter
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- ConsistentHashingShardAllocationStrategy → ShardAllocationStrategy
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- def clusterState: CurrentClusterState
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- ConsistentHashingShardAllocationStrategy → ClusterShardAllocationMixin
- def ensuring(cond: (ConsistentHashingShardAllocationStrategy) => Boolean, msg: => Any): ConsistentHashingShardAllocationStrategy
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- This member is added by an implicit conversion from ConsistentHashingShardAllocationStrategy toEnsuring[ConsistentHashingShardAllocationStrategy] performed by method Ensuring in scala.Predef.
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- def ensuring(cond: (ConsistentHashingShardAllocationStrategy) => Boolean): ConsistentHashingShardAllocationStrategy
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- def ensuring(cond: Boolean, msg: => Any): ConsistentHashingShardAllocationStrategy
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- This member is added by an implicit conversion from ConsistentHashingShardAllocationStrategy toEnsuring[ConsistentHashingShardAllocationStrategy] performed by method Ensuring in scala.Predef.
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- def ensuring(cond: Boolean): ConsistentHashingShardAllocationStrategy
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- final def isAGoodTimeToRebalance(regionEntries: Iterable[RegionEntry]): Boolean
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- 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
ShardRegionand 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
Futureof the shards to be migrated, may be empty to skip rebalance in this round
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- ConsistentHashingShardAllocationStrategy → ShardAllocationStrategy
- final def regionEntriesFor(currentShardAllocations: AllocationMap): Iterable[RegionEntry]
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- 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.
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- def →[B](y: B): (ConsistentHashingShardAllocationStrategy, B)
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