akka.contrib.pattern.ShardCoordinator
Invoked when the location of a new shard is to be decided.
Invoked when the location of a new shard is to be decided.
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
the id of the shard to allocate
all actor refs to ShardRegion
and their current allocated shards,
in the order they were allocated
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
Invoked periodically to decide which shards to rebalance to another location.
Invoked periodically to decide which shards to rebalance to another location.
all actor refs to ShardRegion
and their current allocated shards,
in the order they were allocated
set of shards that are currently being rebalanced, i.e. you should not include these in the returned set
the shards to be migrated, may be empty to skip rebalance in this round
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 theShardRegion
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. 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.