akka.contrib.pattern
Class ShardCoordinator.LeastShardAllocationStrategy
java.lang.Object
akka.contrib.pattern.ShardCoordinator.LeastShardAllocationStrategy
- All Implemented Interfaces:
- NoSerializationVerificationNeeded, ShardCoordinator.ShardAllocationStrategy, java.io.Serializable
- Enclosing class:
- ShardCoordinator
public static class ShardCoordinator.LeastShardAllocationStrategy
- extends java.lang.Object
- implements ShardCoordinator.ShardAllocationStrategy, scala.Serializable
The default implementation of ShardCoordinator.LeastShardAllocationStrategy
allocates new shards to the ShardRegion
with least number of previously allocated shards.
It picks shards for rebalancing handoff from the ShardRegion
with most number of previously allocated shards.
They will then be allocated to the ShardRegion
with least number of previously allocated shards,
i.e. new members in the cluster. There is a configurable threshold of how large the difference
must be to begin the rebalancing. The number of ongoing rebalancing processes can be limited.
- See Also:
- Serialized Form
Method Summary |
ActorRef |
allocateShard(ActorRef requester,
java.lang.String shardId,
scala.collection.immutable.Map<ActorRef,scala.collection.immutable.IndexedSeq<java.lang.String>> currentShardAllocations)
Invoked when the location of a new shard is to be decided. |
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. |
Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
ShardCoordinator.LeastShardAllocationStrategy
public ShardCoordinator.LeastShardAllocationStrategy(int rebalanceThreshold,
int maxSimultaneousRebalance)
allocateShard
public ActorRef allocateShard(ActorRef requester,
java.lang.String shardId,
scala.collection.immutable.Map<ActorRef,scala.collection.immutable.IndexedSeq<java.lang.String>> currentShardAllocations)
- Description copied from interface:
ShardCoordinator.ShardAllocationStrategy
- Invoked when the location of a new shard is to be decided.
- Specified by:
allocateShard
in interface ShardCoordinator.ShardAllocationStrategy
- Parameters:
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 accessedshardId
- the id of the shard to allocatecurrentShardAllocations
- all actor refs to ShardRegion
and their current allocated shards,
in the order they were allocated
- Returns:
- 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
rebalance
public 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.
- Specified by:
rebalance
in interface ShardCoordinator.ShardAllocationStrategy
- Parameters:
currentShardAllocations
- all actor refs to ShardRegion
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:
- the shards to be migrated, may be empty to skip rebalance in this round