org.apache.storm.streams

Class Stream<T>

java.lang.Object

org.apache.storm.streams.Stream<T>

Type Parameters:

T - the type of the value

Direct Known Subclasses:

PairStream

@InterfaceStability.Unstable
public class Stream<T>
extends Object

Represents a stream of values.

Field Summary

Fields

Modifier and Type	Field and Description
protected static Fields	KEY
protected static Fields	KEY_VALUE
protected org.apache.storm.streams.Node	node
protected String	stream
protected StreamBuilder	streamBuilder
protected static Fields	VALUE

Method Summary

Modifier and Type	Method and Description
<A,R> Stream<R>	aggregate(CombinerAggregator<? super T,A,? extends R> aggregator) Aggregates the values in this stream using the aggregator.
<R> Stream<R>	aggregate(R initialValue, BiFunction<? super R,? super T,? extends R> accumulator, BiFunction<? super R,? super R,? extends R> combiner) Aggregates the values in this stream using the given initial value, accumulator and combiner.
Stream<T>[]	branch(Predicate<? super T>... predicates) Returns an array of streams by splitting the given stream into multiple branches based on the given predicates.
Stream<Long>	count() Counts the number of values in this stream.
Stream<T>	filter(Predicate<? super T> predicate) Returns a stream consisting of the elements of this stream that matches the given filter.
<R> Stream<R>	flatMap(FlatMapFunction<? super T,? extends R> function) Returns a stream consisting of the results of replacing each value of this stream with the contents produced by applying the provided mapping function to each value.
<K,V> PairStream<K,V>	flatMapToPair(PairFlatMapFunction<? super T,? extends K,? extends V> function) Returns a stream consisting of the results of replacing each value of this stream with the key-value pairs produced by applying the provided mapping function to each value.
void	forEach(Consumer<? super T> action) Performs an action for each element of this stream.
<R> Stream<R>	map(Function<? super T,? extends R> function) Returns a stream consisting of the result of applying the given mapping function to the values of this stream.
<K,V> PairStream<K,V>	mapToPair(PairFunction<? super T,? extends K,? extends V> function) Returns a stream of key-value pairs by applying a PairFunction on each value of this stream.
protected Stream<T>	partitionBy(Fields fields, int parallelism)
Stream<T>	peek(Consumer<? super T> action) Returns a stream consisting of the elements of this stream, additionally performing the provided action on each element as they are consumed from the resulting stream.
void	print() Print the values in this stream.
Stream<T>	reduce(Reducer<T> reducer) Performs a reduction on the elements of this stream, by repeatedly applying the reducer.
Stream<T>	repartition(int parallelism) Returns a new stream with the given value of parallelism.
<V> PairStream<T,V>	stateQuery(StreamState<T,V> streamState) Queries the given stream state with the values in this stream as the keys.
void	to(IBasicBolt bolt) Sends the elements of this stream to a bolt.
void	to(IBasicBolt bolt, int parallelism) Sends the elements of this stream to a bolt.
void	to(IRichBolt bolt) Sends the elements of this stream to a bolt.
void	to(IRichBolt bolt, int parallelism) Sends the elements of this stream to a bolt.
Stream<T>	window(Window<?,?> window) Returns a new stream consisting of the elements that fall within the window as specified by the window parameter.

Methods inherited from class java.lang.Object

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

Field Detail

KEY

protected static final Fields KEY

VALUE

protected static final Fields VALUE

KEY_VALUE

protected static final Fields KEY_VALUE

streamBuilder

protected final StreamBuilder streamBuilder

node

protected final org.apache.storm.streams.Node node

stream

protected final String stream

Method Detail

filter

public Stream<T> filter(Predicate<? super T> predicate)

Returns a stream consisting of the elements of this stream that matches the given filter.

Parameters:

predicate - the predicate to apply to each element to determine if it should be included

Returns:

the new stream

map

public <R> Stream<R> map(Function<? super T,? extends R> function)

Returns a stream consisting of the result of applying the given mapping function to the values of this stream.

Parameters:

function - a mapping function to be applied to each value in this stream.

Returns:

the new stream

mapToPair

public <K,V> PairStream<K,V> mapToPair(PairFunction<? super T,? extends K,? extends V> function)

Returns a stream of key-value pairs by applying a PairFunction on each value of this stream.

Type Parameters:

K - the key type

V - the value type

Parameters:

function - the mapping function to be applied to each value in this stream

Returns:

the new stream of key-value pairs

flatMap

public <R> Stream<R> flatMap(FlatMapFunction<? super T,? extends R> function)

Returns a stream consisting of the results of replacing each value of this stream with the contents produced by applying the provided mapping function to each value. This has the effect of applying a one-to-many transformation to the values of the stream, and then flattening the resulting elements into a new stream.

Parameters:

function - a mapping function to be applied to each value in this stream which produces new values.

Returns:

the new stream

flatMapToPair

public <K,V> PairStream<K,V> flatMapToPair(PairFlatMapFunction<? super T,? extends K,? extends V> function)

Returns a stream consisting of the results of replacing each value of this stream with the key-value pairs produced by applying the provided mapping function to each value.

Type Parameters:

K - the key type

V - the value type

Parameters:

function - the mapping function to be applied to each value in this stream which produces new key-value pairs.

Returns:

the new stream of key-value pairs

See Also:

flatMap(FlatMapFunction), mapToPair(PairFunction)

window

public Stream<T> window(Window<?,?> window)

Returns a new stream consisting of the elements that fall within the window as specified by the window parameter. The Window specification could be used to specify sliding or tumbling windows based on time duration or event count. For example,

 // time duration based sliding window
 stream.window(SlidingWindows.of(Duration.minutes(10), Duration.minutes(1));

 // count based sliding window
 stream.window(SlidingWindows.of(Count.(10), Count.of(2)));

 // time duration based tumbling window
 stream.window(TumblingWindows.of(Duration.seconds(10));
 

Parameters:

window - the window configuration

Returns:

the new stream

See Also:

SlidingWindows, TumblingWindows

forEach

public void forEach(Consumer<? super T> action)

Performs an action for each element of this stream.

Parameters:

action - an action to perform on the elements

peek

public Stream<T> peek(Consumer<? super T> action)

Returns a stream consisting of the elements of this stream, additionally performing the provided action on each element as they are consumed from the resulting stream.

Parameters:

action - the action to perform on the element as they are consumed from the stream

Returns:

the new stream

aggregate

public <A,R> Stream<R> aggregate(CombinerAggregator<? super T,A,? extends R> aggregator)

Aggregates the values in this stream using the aggregator. This does a global aggregation of values across all partitions.

If the stream is windowed, the aggregate result is emitted after each window activation and represents the aggregate of elements that fall within that window. If the stream is not windowed, the aggregate result is emitted as each new element in the stream is processed.

Type Parameters:

A - the accumulator type

R - the result type

Parameters:

aggregator - the aggregator

Returns:

the new stream

aggregate

public <R> Stream<R> aggregate(R initialValue,
                               BiFunction<? super R,? super T,? extends R> accumulator,
                               BiFunction<? super R,? super R,? extends R> combiner)

Aggregates the values in this stream using the given initial value, accumulator and combiner. This does a global aggregation of values across all partitions.

If the stream is windowed, the aggregate result is emitted after each window activation and represents the aggregate of elements that fall within that window. If the stream is not windowed, the aggregate result is emitted as each new element in the stream is processed.

Type Parameters:

R - the result type

Parameters:

initialValue - the initial value of the result

accumulator - the accumulator

combiner - the combiner

Returns:

the new stream

count

public Stream<Long> count()

Counts the number of values in this stream. This does a global count of values across all partitions.

If the stream is windowed, the counts are emitted after each window activation and represents the count of elements that fall within that window. If the stream is not windowed, the count is emitted as each new element in the stream is processed.

Returns:

the new stream

reduce

public Stream<T> reduce(Reducer<T> reducer)

Performs a reduction on the elements of this stream, by repeatedly applying the reducer. This does a global reduction of values across all partitions.

If the stream is windowed, the result is emitted after each window activation and represents the reduction of elements that fall within that window. If the stream is not windowed, the result is emitted as each new element in the stream is processed.

Parameters:

reducer - the reducer

Returns:

the new stream

repartition

public Stream<T> repartition(int parallelism)

Returns a new stream with the given value of parallelism. Further operations on this stream would execute at this level of parallelism.

Parameters:

parallelism - the parallelism value

Returns:

the new stream

branch

public Stream<T>[] branch(Predicate<? super T>... predicates)

Returns an array of streams by splitting the given stream into multiple branches based on the given predicates. The predicates are applied in the given order to the values of this stream and the result is forwarded to the corresponding (index based) result stream based on the (index of) predicate that matches.

Note: If none of the predicates match a value, that value is dropped.

Parameters:

predicates - the predicates

Returns:

an array of result streams (branches) corresponding to the given predicates

print

public void print()

Print the values in this stream.

to

public void to(IRichBolt bolt)

Sends the elements of this stream to a bolt. This could be used to plug in existing bolts as sinks in the stream, for e.g. a RedisStoreBolt. The bolt would have a parallelism of 1.

Note: This would provide guarantees only based on what the bolt provides.

Parameters:

bolt - the bolt

to

public void to(IRichBolt bolt,
               int parallelism)

Sends the elements of this stream to a bolt. This could be used to plug in existing bolts as sinks in the stream, for e.g. a RedisStoreBolt.

Note: This would provide guarantees only based on what the bolt provides.

Parameters:

bolt - the bolt

parallelism - the parallelism of the bolt

to

public void to(IBasicBolt bolt)

Sends the elements of this stream to a bolt. This could be used to plug in existing bolts as sinks in the stream, for e.g. a RedisStoreBolt. The bolt would have a parallelism of 1.

Note: This would provide guarantees only based on what the bolt provides.

Parameters:

bolt - the bolt

to

public void to(IBasicBolt bolt,
               int parallelism)

Sends the elements of this stream to a bolt. This could be used to plug in existing bolts as sinks in the stream, for e.g. a RedisStoreBolt.

Note: This would provide guarantees only based on what the bolt provides.

Parameters:

bolt - the bolt

parallelism - the parallelism of the bolt

stateQuery

public <V> PairStream<T,V> stateQuery(StreamState<T,V> streamState)

Queries the given stream state with the values in this stream as the keys.

Type Parameters:

V - the value type

Parameters:

streamState - the stream state

Returns:

the result stream

partitionBy

protected Stream<T> partitionBy(Fields fields,
                                int parallelism)