Package org.apache.pekko.cluster.sharding.typed

Class ShardingMessageExtractor<E,M>

java.lang.Object

org.apache.pekko.cluster.sharding.typed.ShardingMessageExtractor<E,M>

Type Parameters:

E - Possibly an Envelope around the messages accepted by the entity actor, is the same as M if there is no envelope.

M - The type of message accepted by the entity actor

Direct Known Subclasses:

HashCodeMessageExtractor, HashCodeNoEnvelopeMessageExtractor, Murmur2MessageExtractor, Murmur2NoEnvelopeMessageExtractor

public abstract class ShardingMessageExtractor<E,M>
extends Object

Entirely customizable typed message extractor. Prefer HashCodeMessageExtractor or HashCodeNoEnvelopeMessageExtractorif possible.

Constructor Summary

Constructors

Constructor	Description
ShardingMessageExtractor()

Method Summary

Modifier and Type	Method	Description
static <M> ShardingMessageExtractor<ShardingEnvelope<M>,M>	apply(int numberOfShards)	Scala API:
abstract String	entityId(E message)	Extract the entity id from an incoming message.
static <M> ShardingMessageExtractor<M,M>	noEnvelope(int numberOfShards, M stopMessage, scala.Function1<M,String> extractEntityId)	Scala API: Create a message extractor for a protocol where the entity id is available in each message.
abstract String	shardId(String entityId)	The shard identifier for a given entity id.
abstract M	unwrapMessage(E message)	Extract the message to send to the entity from an incoming message.

Methods inherited from class java.lang.Object

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

Constructor Details

ShardingMessageExtractor

public ShardingMessageExtractor()

Method Details

apply

public static <M>
ShardingMessageExtractor<ShardingEnvelope<M>,M> apply(int numberOfShards)

Scala API:

Create the default message extractor, using envelopes to identify what entity a message is for and the hashcode of the entityId to decide which shard an entity belongs to.

This is recommended since it does not force details about sharding into the entity protocol

noEnvelope

public static <M> ShardingMessageExtractor<M,M> noEnvelope(int numberOfShards,
 M stopMessage,
 scala.Function1<M,String> extractEntityId)

Scala API: Create a message extractor for a protocol where the entity id is available in each message.

entityId

public abstract String entityId(E message)

Extract the entity id from an incoming message. If null is returned the message will be unhandled, i.e. posted as Unhandled messages on the event stream

shardId

public abstract String shardId(String entityId)

The shard identifier for a given entity id. Only messages that passed the entityId(E) function will be used as input to this function.

unwrapMessage

public abstract M unwrapMessage(E message)

Extract the message to send to the entity from an incoming message. Note that the extracted message does not have to be the same as the incoming message to support wrapping in message envelope that is unwrapped before sending to the entity actor.