com.salesforce.reactivegrpc.common

Class AbstractStreamObserverAndPublisher<T>

java.lang.Object

com.salesforce.reactivegrpc.common.AbstractUnimplementedQueue<T>

com.salesforce.reactivegrpc.common.AbstractStreamObserverAndPublisher<T>

Type Parameters:

T - T

All Implemented Interfaces:

io.grpc.stub.StreamObserver<T>, Iterable<T>, Collection<T>, Queue<T>, org.reactivestreams.Publisher<T>, org.reactivestreams.Subscription

Direct Known Subclasses:

AbstractClientStreamObserverAndPublisher, AbstractServerStreamObserverAndPublisher

public abstract class AbstractStreamObserverAndPublisher<T>
extends AbstractUnimplementedQueue<T>
implements org.reactivestreams.Publisher<T>, io.grpc.stub.StreamObserver<T>, org.reactivestreams.Subscription, Queue<T>

AbstractStreamObserverAndPublisher bridges the manual flow control idioms of gRPC and Reactive Streams. This class takes messages off of a CallStreamObserver and feeds them into a Publisher while respecting backpressure. In order to keep backpressure working at the async boundary between CallStreamObserver as an upstream, the AbstractSubscriberAndProducer enable manual flow-control by calling CallStreamObserver.disableAutoInboundFlowControl() at subscription time and prefetch specified by prefetch number of elements at first and then keeps the number of requested element on the same level once the upstream sent amount of elements reach the specified limit. In addition, AbstractStreamObserverAndPublisher take an additional care for some exotic cases when upstream does not respect backpressure of the Reactive-Streams Subscriber as the downstream, so AbstractStreamObserverAndPublisher employees Queue that enqueue each incoming elements and in that way keeps excess of items. In turn, to avoid Queue overwhelming, it is recommended to uses Queue with a fixed size so in the case Queue.offer(Object) returns false the sender thread will be blocked with a busy spin using LockSupport.parkNanos(long) try to enqueue element into Queue until downstream deque element from it.

Field Summary

Fields

Modifier and Type	Field and Description
static int	DEFAULT_CHUNK_SIZE
protected boolean	outputFused
protected io.grpc.stub.CallStreamObserver<?>	subscription
static int	TWO_THIRDS_OF_DEFAULT_CHUNK_SIZE

Method Summary

Modifier and Type	Method and Description
void	cancel()
void	clear()
protected void	doOnCancel()
boolean	isCancelled()
boolean	isEmpty()
void	onCompleted()
void	onError(Throwable t)
void	onNext(T t)
protected void	onSubscribe(io.grpc.stub.CallStreamObserver<?> upstream)
T	poll()
void	request(long n)
int	size()
void	subscribe(org.reactivestreams.Subscriber<? super T> actual)

Methods inherited from class com.salesforce.reactivegrpc.common.AbstractUnimplementedQueue

add, addAll, contains, containsAll, element, iterator, offer, offer, peek, remove, remove, removeAll, retainAll, toArray, toArray

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.Queue

add, element, offer, peek, remove

Methods inherited from interface java.util.Collection

addAll, contains, containsAll, equals, hashCode, iterator, parallelStream, remove, removeAll, removeIf, retainAll, spliterator, stream, toArray, toArray

Methods inherited from interface java.lang.Iterable

forEach

Field Detail

DEFAULT_CHUNK_SIZE

public static final int DEFAULT_CHUNK_SIZE

See Also:

Constant Field Values

TWO_THIRDS_OF_DEFAULT_CHUNK_SIZE

public static final int TWO_THIRDS_OF_DEFAULT_CHUNK_SIZE

See Also:

Constant Field Values

outputFused

protected volatile boolean outputFused

subscription

protected volatile io.grpc.stub.CallStreamObserver<?> subscription

Method Detail

onSubscribe

protected void onSubscribe(io.grpc.stub.CallStreamObserver<?> upstream)

onNext

public void onNext(T t)

Specified by:

onNext in interface io.grpc.stub.StreamObserver<T>

onError

public void onError(Throwable t)

Specified by:

onError in interface io.grpc.stub.StreamObserver<T>

onCompleted

public void onCompleted()

Specified by:

onCompleted in interface io.grpc.stub.StreamObserver<T>

subscribe

public void subscribe(org.reactivestreams.Subscriber<? super T> actual)

Specified by:

subscribe in interface org.reactivestreams.Publisher<T>

isCancelled

public boolean isCancelled()

request

public void request(long n)

Specified by:

request in interface org.reactivestreams.Subscription

cancel

public void cancel()

Specified by:

cancel in interface org.reactivestreams.Subscription

doOnCancel

protected void doOnCancel()

poll

public T poll()

Specified by:

poll in interface Queue<T>

Overrides:

poll in class AbstractUnimplementedQueue<T>

size

public int size()

Specified by:

size in interface Collection<T>

Overrides:

size in class AbstractUnimplementedQueue<T>

isEmpty

public boolean isEmpty()

Specified by:

isEmpty in interface Collection<T>

clear

public void clear()

Specified by:

clear in interface Collection<T>