Class LeastShardAllocationStrategy
- java.lang.Object
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- akka.cluster.sharding.internal.AbstractLeastShardAllocationStrategy
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- akka.cluster.sharding.internal.LeastShardAllocationStrategy
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- All Implemented Interfaces:
NoSerializationVerificationNeeded
,ShardCoordinator.ActorSystemDependentAllocationStrategy
,ShardCoordinator.ShardAllocationStrategy
public class LeastShardAllocationStrategy extends AbstractLeastShardAllocationStrategy
INTERNAL API: UseShardCoordinator.ShardAllocationStrategy.leastShardAllocationStrategy
factory method.ShardAllocationStrategy
that allocates new shards to theShardRegion
(node) with least number of previously allocated shards.When a node is added to the cluster the shards on the existing nodes will be rebalanced to the new node. The
LeastShardAllocationStrategy
picks shards for rebalancing from theShardRegion
s with most number of previously allocated shards. They will then be allocated to theShardRegion
with least number of previously allocated shards, i.e. new members in the cluster. The amount of shards to rebalance in each round can be limited to make it progress slower since rebalancing too many shards at the same time could result in additional load on the system. For example, causing many Event Sourced entites to be started at the same time.It will not rebalance when there is already an ongoing rebalance in progress.
param: absoluteLimit the maximum number of shards that will be rebalanced in one rebalance round param: relativeLimit fraction (< 1.0) of total number of (known) shards that will be rebalanced in one rebalance round
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Nested Class Summary
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Nested classes/interfaces inherited from class akka.cluster.sharding.internal.AbstractLeastShardAllocationStrategy
AbstractLeastShardAllocationStrategy.RegionEntry, AbstractLeastShardAllocationStrategy.RegionEntry$, AbstractLeastShardAllocationStrategy.ShardSuitabilityOrdering$
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Constructor Summary
Constructors Constructor Description LeastShardAllocationStrategy(int absoluteLimit, double relativeLimit)
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description scala.concurrent.Future<scala.collection.immutable.Set<java.lang.String>>
rebalance(scala.collection.immutable.Map<ActorRef,scala.collection.immutable.IndexedSeq<java.lang.String>> currentShardAllocations, scala.collection.immutable.Set<java.lang.String> rebalanceInProgress)
Invoked periodically to decide which shards to rebalance to another location.java.lang.String
toString()
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Methods inherited from class akka.cluster.sharding.internal.AbstractLeastShardAllocationStrategy
allocateShard, clusterState, isAGoodTimeToRebalance, mostSuitableRegion, regionEntriesFor, selfMember, start
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Method Detail
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rebalance
public scala.concurrent.Future<scala.collection.immutable.Set<java.lang.String>> rebalance(scala.collection.immutable.Map<ActorRef,scala.collection.immutable.IndexedSeq<java.lang.String>> currentShardAllocations, scala.collection.immutable.Set<java.lang.String> rebalanceInProgress)
Description copied from interface:ShardCoordinator.ShardAllocationStrategy
Invoked periodically to decide which shards to rebalance to another location.- Parameters:
currentShardAllocations
- all actor refs toShardRegion
and their current allocated shards, in the order they were allocatedrebalanceInProgress
- 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
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toString
public java.lang.String toString()
- Overrides:
toString
in classjava.lang.Object
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