Package org.apache.pekko.stream.javadsl

Class BroadcastHub

java.lang.Object

org.apache.pekko.stream.javadsl.BroadcastHub

public class BroadcastHub
extends Object

A BroadcastHub is a special streaming hub that is able to broadcast streamed elements to a dynamic set of consumers. It consists of two parts, a Sink and a Source. The Sink broadcasts elements from a producer to the actually live consumers it has. Once the producer has been materialized, the Sink it feeds into returns a materialized value which is the corresponding Source. This Source can be materialized an arbitrary number of times, where each of the new materializations will receive their elements from the original Sink.

Constructor Summary

Constructors

Constructor	Description
BroadcastHub()

Method Summary

Modifier and Type	Method	Description
static <T> Sink<T,Source<T,NotUsed>>	of(Class<T> clazz)	Creates a Sink with default buffer size 256 that receives elements from its upstream producer and broadcasts them to a dynamic set of consumers.
static <T> Sink<T,Source<T,NotUsed>>	of(Class<T> clazz, int bufferSize)	Creates a Sink that receives elements from its upstream producer and broadcasts them to a dynamic set of consumers.
static <T> Sink<T,Source<T,NotUsed>>	of(Class<T> clazz, int startAfterNrOfConsumers, int bufferSize)	Creates a Sink that receives elements from its upstream producer and broadcasts them to a dynamic set of consumers.

Methods inherited from class java.lang.Object

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

Constructor Details

BroadcastHub

public BroadcastHub()

Method Details

of

public static <T> Sink<T,Source<T,NotUsed>> of(Class<T> clazz,
 int bufferSize)

Creates a Sink that receives elements from its upstream producer and broadcasts them to a dynamic set of consumers. After the Sink returned by this method is materialized, it returns a Source as materialized value. This Source can be materialized an arbitrary number of times and each materialization will receive the broadcast elements from the original Sink.

Every new materialization of the Sink results in a new, independent hub, which materializes to its own Source for consuming the Sink of that materialization.

If the original Sink is failed, then the failure is immediately propagated to all of its materialized Sources (possibly jumping over already buffered elements). If the original Sink is completed, then all corresponding Sources are completed. Both failure and normal completion is "remembered" and later materializations of the Source will see the same (failure or completion) state. Sources that are cancelled are simply removed from the dynamic set of consumers.

Parameters:

clazz - Type of elements this hub emits and consumes

bufferSize - Buffer size used by the producer. Gives an upper bound on how "far" from each other two concurrent consumers can be in terms of element. If the buffer is full, the producer is backpressured. Must be a power of two and less than 4096.

of

public static <T> Sink<T,Source<T,NotUsed>> of(Class<T> clazz,
 int startAfterNrOfConsumers,
 int bufferSize)

Creates a Sink that receives elements from its upstream producer and broadcasts them to a dynamic set of consumers. After the Sink returned by this method is materialized, it returns a Source as materialized value. This Source can be materialized an arbitrary number of times and each materialization will receive the broadcast elements from the original Sink.

Every new materialization of the Sink results in a new, independent hub, which materializes to its own Source for consuming the Sink of that materialization.

If the original Sink is failed, then the failure is immediately propagated to all of its materialized Sources (possibly jumping over already buffered elements). If the original Sink is completed, then all corresponding Sources are completed. Both failure and normal completion is "remembered" and later materializations of the Source will see the same (failure or completion) state. Sources that are cancelled are simply removed from the dynamic set of consumers.

Parameters:

clazz - Type of elements this hub emits and consumes

startAfterNrOfConsumers - Elements are buffered until this number of consumers have been connected. This is only used initially when the operator is starting up, i.e. it is not honored when consumers have been removed (canceled).

bufferSize - Buffer size used by the producer. Gives an upper bound on how "far" from each other two concurrent consumers can be in terms of element. If the buffer is full, the producer is backpressured. Must be a power of two and less than 4096.

Since:

1.1.0

of

public static <T> Sink<T,Source<T,NotUsed>> of(Class<T> clazz)

Creates a Sink with default buffer size 256 that receives elements from its upstream producer and broadcasts them to a dynamic set of consumers. After the Sink returned by this method is materialized, it returns a Source as materialized value. This Source can be materialized an arbitrary number of times and each materialization will receive the broadcast elements from the original Sink.

Every new materialization of the Sink results in a new, independent hub, which materializes to its own Source for consuming the Sink of that materialization.

If the original Sink is failed, then the failure is immediately propagated to all of its materialized Sources (possibly jumping over already buffered elements). If the original Sink is completed, then all corresponding Sources are completed. Both failure and normal completion is "remembered" and later materializations of the Source will see the same (failure or completion) state. Sources that are cancelled are simply removed from the dynamic set of consumers.

Parameters:

clazz - Type of elements this hub emits and consumes