class SliceRangeShardAllocationStrategy extends ActorSystemDependentAllocationStrategy with ClusterShardAllocationMixin
Intended to be used with database sharding, https://doc.akka.io/libraries/akka-persistence-r2dbc/current/data-partition.html, with a cluster of many Akka nodes. To avoid that each Akka node has database connections to all databases it is preferred to collocate entities with the same slice and contiguous range of slices to the same Akka node. Thereby the connections from one Akka node will go to one or a few databases since the database sharding is based on slice ranges.
It must be used together with the SliceRangeShardAllocationStrategy.ShardBySliceMessageExtractor.
Create a new instance of this for each entity type, i.e. a SliceRangeShardAllocationStrategy
instance must not be shared between different entity types.
It will not rebalance when there is already an ongoing rebalance in progress.
Important: Do not change shard allocation strategy in a rolling update. The cluster must be fully stopped and then started again when changing to a different allocation strategy.
Not intended for public inheritance/implementation.
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- SliceRangeShardAllocationStrategy.scala
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- This member is added by an implicit conversion from SliceRangeShardAllocationStrategy toany2stringadd[SliceRangeShardAllocationStrategy] performed by method any2stringadd in scala.Predef.
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- def ->[B](y: B): (SliceRangeShardAllocationStrategy, B)
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- This member is added by an implicit conversion from SliceRangeShardAllocationStrategy toArrowAssoc[SliceRangeShardAllocationStrategy] 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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- SliceRangeShardAllocationStrategy → ShardAllocationStrategy
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- def clusterState: CurrentClusterState
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- SliceRangeShardAllocationStrategy → ClusterShardAllocationMixin
- def ensuring(cond: (SliceRangeShardAllocationStrategy) => Boolean, msg: => Any): SliceRangeShardAllocationStrategy
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- This member is added by an implicit conversion from SliceRangeShardAllocationStrategy toEnsuring[SliceRangeShardAllocationStrategy] performed by method Ensuring in scala.Predef.
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- def ensuring(cond: (SliceRangeShardAllocationStrategy) => Boolean): SliceRangeShardAllocationStrategy
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- This member is added by an implicit conversion from SliceRangeShardAllocationStrategy toEnsuring[SliceRangeShardAllocationStrategy] performed by method Ensuring in scala.Predef.
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- def ensuring(cond: Boolean, msg: => Any): SliceRangeShardAllocationStrategy
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- This member is added by an implicit conversion from SliceRangeShardAllocationStrategy toEnsuring[SliceRangeShardAllocationStrategy] performed by method Ensuring in scala.Predef.
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- def ensuring(cond: Boolean): SliceRangeShardAllocationStrategy
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- This member is added by an implicit conversion from SliceRangeShardAllocationStrategy toEnsuring[SliceRangeShardAllocationStrategy] performed by method Ensuring in scala.Predef.
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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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- SliceRangeShardAllocationStrategy → 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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- SliceRangeShardAllocationStrategy → ActorSystemDependentAllocationStrategy
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(Since version 9)
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- This member is added by an implicit conversion from SliceRangeShardAllocationStrategy toStringFormat[SliceRangeShardAllocationStrategy] performed by method StringFormat in scala.Predef.
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(Since version 2.12.16) Use
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- def →[B](y: B): (SliceRangeShardAllocationStrategy, B)
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