com.hazelcast.jet.pipeline

Class SourceBuilder.Stream<T>

java.lang.Object

com.hazelcast.jet.pipeline.SourceBuilder.Stream<T>

Type Parameters:

T - type of emitted objects

Enclosing class:

SourceBuilder<C>

public final class SourceBuilder.Stream<T>
extends Object

See SourceBuilder.stream(String, FunctionEx).

Since:

Jet 3.0

Method Summary

Modifier and Type	Method and Description
StreamSource<T>	build() Builds and returns the unbounded stream source.
<S> SourceBuilder.FaultTolerant<SourceBuilder.Stream<T>,S>	createSnapshotFn(FunctionEx<? super C,? extends S> createSnapshotFn) Sets the function Jet calls when it's creating a snapshot of the current job state.
SourceBuilder.Stream<T>	destroyFn(ConsumerEx<? super C> pDestroyFn) Sets the function that Jet will call when it is done cleaning up after an execution.
SourceBuilder.Stream<T>	distributed(int preferredLocalParallelism) Declares that you're creating a distributed source.
<T_NEW> SourceBuilder.Stream<T_NEW>	fillBufferFn(BiConsumerEx<? super C,? super SourceBuilder.SourceBuffer<T_NEW>> fillBufferFn) Sets the function that Jet will call whenever it needs more data from your source.
SourceBuilder.Stream<T>	permission(Permission permission) Sets the the permission required to use this sink when the security is enabled.

Methods inherited from class java.lang.Object

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

Method Detail

fillBufferFn

@Nonnull
public <T_NEW> SourceBuilder.Stream<T_NEW> fillBufferFn(@Nonnull
                                                                 BiConsumerEx<? super C,? super SourceBuilder.SourceBuffer<T_NEW>> fillBufferFn)

Sets the function that Jet will call whenever it needs more data from your source. The function receives the context object obtained from createFn and Jet's buffer object. It should add some items to the buffer, ideally those it can produce without making any blocking calls. On any given invocation the function may also choose not to add any items. Jet will automatically employ an exponential backoff strategy to avoid calling your function in a tight loop, if the previous call didn't add any items to the buffer.

The given SourceBuilder.SourceBuffer isn't thread-safe, you shouldn't pass it to other threads. For example, you shouldn't add to it in a callback of an asynchronous operation.

Type Parameters:

T_NEW - type of the emitted items

Parameters:

fillBufferFn - function that fills the buffer with source data. It must be stateless.

Returns:

this builder with the item type reset to the one inferred from fillBufferFn

destroyFn

@Nonnull
public SourceBuilder.Stream<T> destroyFn(@Nonnull
                                                  ConsumerEx<? super C> pDestroyFn)

Sets the function that Jet will call when it is done cleaning up after an execution. It gives you the opportunity to release any resources that your context object may be holding. Jet also calls this function when the user cancels or restarts the job.

The function must be stateless.

distributed

@Nonnull
public SourceBuilder.Stream<T> distributed(int preferredLocalParallelism)

Declares that you're creating a distributed source. On each member of the cluster Jet will create as many processors as you specify with the preferredLocalParallelism parameter. If you call this, you must ensure that all the source processors are coordinated and not emitting duplicated data. The createFn can consult processorContext.totalParallelism() and Processor.Context#globalProcessorIndex(). Jet calls createFn exactly once with each globalProcessorIndex from 0 to totalParallelism - 1 and you can use this to make all the instances agree on which part of the data to emit.

If you don't call this method, there will be only one processor instance running on an arbitrary member.

Parameters:

preferredLocalParallelism - the requested number of processors on each cluster member

permission

public SourceBuilder.Stream<T> permission(@Nonnull
                                          Permission permission)

Sets the the permission required to use this sink when the security is enabled. The default value is null which means there is no restriction to use this sink. Security is an enterprise feature.

Parameters:

permission - the required permission to use this sink when security is enabled.

createSnapshotFn

@Nonnull
public <S> SourceBuilder.FaultTolerant<SourceBuilder.Stream<T>,S> createSnapshotFn(@Nonnull
                                                                                            FunctionEx<? super C,? extends S> createSnapshotFn)

Sets the function Jet calls when it's creating a snapshot of the current job state. This happens in all Jet jobs that have a processing guarantee configured.

When Jet restarts a job, it first initializes your source as if starting a new job, and then passes the snapshot object you returned here to restoreSnapshotFn. After that it starts calling fillBufferFn, which must resume emitting the stream from the same item it was about to emit when the snapshot was taken.

The object you return must be serializable. Each source processor will call the function once per snapshot.

Here's an example of a fault-tolerant generator of an infinite sequence of integers:

 StreamSource<Integer> source = SourceBuilder
         .stream("name", processorContext -> new AtomicInteger())
         .<Integer>fillBufferFn((numToEmit, buffer) -> {
             for (int i = 0; i < 100; i++) {
                 buffer.add(numToEmit.getAndIncrement());
             }
         })
         .createSnapshotFn(numToEmit -> numToEmit.get())
         .restoreSnapshotFn((numToEmit, states) -> numToEmit.set(states.get(0)))
         .build();
 

Type Parameters:

S - type of the snapshot object

Parameters:

createSnapshotFn - a function to create an object to store in the state snapshot. It must be stateless.

build

@Nonnull
public StreamSource<T> build()

Builds and returns the unbounded stream source.