io.spine.server.delivery

Class UniformAcrossAllShards

java.lang.Object

io.spine.server.delivery.DeliveryStrategy

io.spine.server.delivery.UniformAcrossAllShards

All Implemented Interfaces:

java.io.Serializable

@Immutable
public final class UniformAcrossAllShards
extends DeliveryStrategy
implements java.io.Serializable

The strategy of splitting the entities into a number of shards uniformly.

Uses a hash code of the entity identifier and the remainder of its division by the total number of shards to determine the index of a shard, at which the modification is allowed. To reach the consistency of the hash code values across JVMs, the MurmurHash3, x86 variant is used.

While Guava's Hashing is marked @Beta, it is still the best option for hashing functions — not to involve any heavy-weight third-party hashing solutions.

See Also:

Serialized Form

Method Summary

Modifier and Type	Method and Description
static DeliveryStrategy	forNumber(int totalShards) Creates a strategy of uniform target distribution across shards, for a given shard number.
io.spine.server.delivery.ShardIndex	indexFor(java.lang.Object entityId, io.spine.type.TypeUrl entityStateType) Determines the shard index for the messages heading to the entity with the specified target identifier.
int	shardCount() Tells how many shards there are according to this strategy.
static DeliveryStrategy	singleShard() Returns a pre-defined strategy instance, which defines a single shard and puts all the targets into it.

Methods inherited from class io.spine.server.delivery.DeliveryStrategy

determineIndex

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

forNumber

public static DeliveryStrategy forNumber(int totalShards)

Creates a strategy of uniform target distribution across shards, for a given shard number.

Parameters:

totalShards - a number of shards

Returns:

a uniform distribution strategy instance for a given shard number

indexFor

public io.spine.server.delivery.ShardIndex indexFor(java.lang.Object entityId,
                                                    io.spine.type.TypeUrl entityStateType)

Description copied from class: DeliveryStrategy

Determines the shard index for the messages heading to the entity with the specified target identifier.

Specified by:

indexFor in class DeliveryStrategy

Parameters:

entityId - the identifier of the entity, to which the messages are dispatched

entityStateType - the type URL of the entity, to which the messages are dispatched

Returns:

the shard index

shardCount

public int shardCount()

Description copied from class: DeliveryStrategy

Tells how many shards there are according to this strategy.

Specified by:

shardCount in class DeliveryStrategy

Returns:

total count of shards

singleShard

public static DeliveryStrategy singleShard()

Returns a pre-defined strategy instance, which defines a single shard and puts all the targets into it.

Returns:

a strategy that puts all entities in a single shard