Class PartitionHub
- java.lang.Object
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- akka.stream.javadsl.PartitionHub
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public class PartitionHub extends java.lang.Object
Creates aSink
that receives elements from its upstream producer and routes them to a dynamic set of consumers. After theSink
returned by this method is materialized, it returns aSource
as materialized value. ThisSource
can be materialized an arbitrary number of times and each materialization will receive the elements from the originalSink
.Every new materialization of the
Sink
results in a new, independent hub, which materializes to its ownSource
for consuming theSink
of that materialization.If the original
Sink
is failed, then the failure is immediately propagated to all of its materializedSource
s (possibly jumping over already buffered elements). If the originalSink
is completed, then all correspondingSource
s are completed. Both failure and normal completion is "remembered" and later materializations of theSource
will see the same (failure or completion) state.Source
s that are cancelled are simply removed from the dynamic set of consumers.This
statefulSink
should be used when there is a need to keep mutable state in the partition function, e.g. for implemening round-robin or sticky session kind of routing. If state is not needed theof(java.lang.Class<T>, java.util.function.BiFunction<java.lang.Integer, T, java.lang.Integer>, int, int)
can be more convenient to use.param: partitioner Function that decides where to route an element. It is a factory of a function to to be able to hold stateful variables that are unique for each materialization. The function takes two parameters; the first is information about active consumers, including an array of consumer identifiers and the second is the stream element. The function should return the selected consumer identifier for the given element. The function will never be called when there are no active consumers, i.e. there is always at least one element in the array of identifiers. param: 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). param: bufferSize Total number of elements that can be buffered. If this buffer is full, the producer is backpressured.
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Nested Class Summary
Nested Classes Modifier and Type Class Description static interface
PartitionHub.ConsumerInfo
Sequence of all identifiers of current consumers.
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Constructor Summary
Constructors Constructor Description PartitionHub()
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Method Summary
All Methods Static Methods Concrete Methods Modifier and Type Method Description static <T> Sink<T,Source<T,NotUsed>>
of(java.lang.Class<T> clazz, java.util.function.BiFunction<java.lang.Integer,T,java.lang.Integer> partitioner, int startAfterNrOfConsumers)
static <T> Sink<T,Source<T,NotUsed>>
of(java.lang.Class<T> clazz, java.util.function.BiFunction<java.lang.Integer,T,java.lang.Integer> partitioner, int startAfterNrOfConsumers, int bufferSize)
Creates aSink
that receives elements from its upstream producer and routes them to a dynamic set of consumers.static <T> Sink<T,Source<T,NotUsed>>
ofStateful(java.lang.Class<T> clazz, java.util.function.Supplier<java.util.function.ToLongBiFunction<PartitionHub.ConsumerInfo,T>> partitioner, int startAfterNrOfConsumers)
static <T> Sink<T,Source<T,NotUsed>>
ofStateful(java.lang.Class<T> clazz, java.util.function.Supplier<java.util.function.ToLongBiFunction<PartitionHub.ConsumerInfo,T>> partitioner, int startAfterNrOfConsumers, int bufferSize)
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Method Detail
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ofStateful
public static <T> Sink<T,Source<T,NotUsed>> ofStateful(java.lang.Class<T> clazz, java.util.function.Supplier<java.util.function.ToLongBiFunction<PartitionHub.ConsumerInfo,T>> partitioner, int startAfterNrOfConsumers, int bufferSize)
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ofStateful
public static <T> Sink<T,Source<T,NotUsed>> ofStateful(java.lang.Class<T> clazz, java.util.function.Supplier<java.util.function.ToLongBiFunction<PartitionHub.ConsumerInfo,T>> partitioner, int startAfterNrOfConsumers)
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of
public static <T> Sink<T,Source<T,NotUsed>> of(java.lang.Class<T> clazz, java.util.function.BiFunction<java.lang.Integer,T,java.lang.Integer> partitioner, int startAfterNrOfConsumers, int bufferSize)
Creates aSink
that receives elements from its upstream producer and routes them to a dynamic set of consumers. After theSink
returned by this method is materialized, it returns aSource
as materialized value. ThisSource
can be materialized an arbitrary number of times and each materialization will receive the elements from the originalSink
.Every new materialization of the
Sink
results in a new, independent hub, which materializes to its ownSource
for consuming theSink
of that materialization.If the original
Sink
is failed, then the failure is immediately propagated to all of its materializedSource
s (possibly jumping over already buffered elements). If the originalSink
is completed, then all correspondingSource
s are completed. Both failure and normal completion is "remembered" and later materializations of theSource
will see the same (failure or completion) state.Source
s that are cancelled are simply removed from the dynamic set of consumers.This
sink
should be used when the routing function is stateless, e.g. based on a hashed value of the elements. Otherwise theofStateful(java.lang.Class<T>, java.util.function.Supplier<java.util.function.ToLongBiFunction<akka.stream.javadsl.PartitionHub.ConsumerInfo, T>>, int, int)
can be used to implement more advanced routing logic.- Parameters:
partitioner
- Function that decides where to route an element. The function takes two parameters; the first is the number of active consumers and the second is the stream element. The function should return the index of the selected consumer for the given element, i.e. int greater than or equal to 0 and less than number of consumers. E.g.(size, elem) -> Math.abs(elem.hashCode() % size)
. It's also possible to use-1
to drop the element.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
- Total number of elements that can be buffered. If this buffer is full, the producer is backpressured.clazz
- (undocumented)- Returns:
- (undocumented)
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