/*
* Copyright (c) 2011-2017 Pivotal Software Inc, All Rights Reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package reactor.core.publisher;
import java.util.Objects;
import java.util.Queue;
import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
import java.util.concurrent.atomic.AtomicLongFieldUpdater;
import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
import java.util.function.Function;
import java.util.function.Supplier;
import java.util.stream.Stream;
import org.reactivestreams.Publisher;
import org.reactivestreams.Subscriber;
import org.reactivestreams.Subscription;
import reactor.core.Exceptions;
import reactor.core.Fuseable;
import reactor.core.Fuseable.QueueSubscription;
import reactor.core.Scannable;
import reactor.core.publisher.FluxConcatMap.ErrorMode;
import reactor.util.concurrent.QueueSupplier;
/**
* Maps each upstream value into a Publisher and concatenates them into one
* sequence of items.
*
* @param <T> the source value type
* @param <R> the output value type
* @see <a href="https://github.com/reactor/reactive-streams-commons">Reactive-Streams-Commons</a>
*/
final class FluxMergeSequential<T, R> extends FluxSource<T, R> {
final ErrorMode errorMode;
final Function<? super T, ? extends Publisher<? extends R>> mapper;
final int maxConcurrency;
final int prefetch;
final Supplier<Queue<MergeSequentialInner<R>>> queueSupplier;
FluxMergeSequential(Publisher<? extends T> source,
Function<? super T, ? extends Publisher<? extends R>> mapper,
int maxConcurrency, int prefetch, ErrorMode errorMode) {
this(source, mapper, maxConcurrency, prefetch, errorMode,
QueueSupplier.get(Math.max(prefetch, maxConcurrency)));
}
//for testing purpose
FluxMergeSequential(Publisher<? extends T> source,
Function<? super T, ? extends Publisher<? extends R>> mapper,
int maxConcurrency, int prefetch, ErrorMode errorMode,
Supplier<Queue<MergeSequentialInner<R>>> queueSupplier) {
super(source);
if (prefetch <= 0) {
throw new IllegalArgumentException("prefetch > 0 required but it was " + prefetch);
}
if (maxConcurrency <= 0) {
throw new IllegalArgumentException("maxConcurrency > 0 required but it was " + maxConcurrency);
}
this.mapper = Objects.requireNonNull(mapper, "mapper");
this.maxConcurrency = maxConcurrency;
this.prefetch = prefetch;
this.errorMode = errorMode;
this.queueSupplier = queueSupplier;
}
@Override
public void subscribe(Subscriber<? super R> s) {
if (FluxFlatMap.trySubscribeScalarMap(source, s, mapper, false)) {
return;
}
Subscriber<T> parent = new MergeSequentialMain<T, R>(s,
mapper,
maxConcurrency,
prefetch,
errorMode,
queueSupplier);
source.subscribe(parent);
}
static final class MergeSequentialMain<T, R>
implements InnerOperator<T, R>, InnerProducer<R> {
/** the mapper giving the inner publisher for each source value */
final Function<? super T, ? extends Publisher<? extends R>> mapper;
/** how many eagerly subscribed inner stream at a time, at most */
final int maxConcurrency;
/** request size for inner subscribers (size of the inner queues) */
final int prefetch;
final Queue<MergeSequentialInner<R>> subscribers;
/** whether or not errors should be delayed until the very end of all inner
* publishers or just until the completion of the currently merged inner publisher
*/
final ErrorMode errorMode;
final Subscriber<? super R> actual;
Subscription s;
volatile boolean done;
volatile boolean cancelled;
volatile Throwable error;
static final AtomicReferenceFieldUpdater<MergeSequentialMain, Throwable> ERROR =
AtomicReferenceFieldUpdater.newUpdater(MergeSequentialMain.class, Throwable.class, "error");
MergeSequentialInner<R> current;
/** guard against multiple threads entering the drain loop. allows thread
* stealing by continuing the loop if wip has been incremented externally by
* a separate thread. */
volatile int wip;
static final AtomicIntegerFieldUpdater<MergeSequentialMain> WIP =
AtomicIntegerFieldUpdater.newUpdater(MergeSequentialMain.class, "wip");
volatile long requested;
static final AtomicLongFieldUpdater<MergeSequentialMain> REQUESTED =
AtomicLongFieldUpdater.newUpdater(MergeSequentialMain.class, "requested");
MergeSequentialMain(Subscriber<? super R> actual,
Function<? super T, ? extends Publisher<? extends R>> mapper,
int maxConcurrency, int prefetch, ErrorMode errorMode,
Supplier<Queue<MergeSequentialInner<R>>> queueSupplier) {
this.actual = actual;
this.mapper = mapper;
this.maxConcurrency = maxConcurrency;
this.prefetch = prefetch;
this.errorMode = errorMode;
this.subscribers = queueSupplier.get();
}
@Override
public Stream<? extends Scannable> inners() {
return Stream.of(subscribers.peek());
}
@Override
public final Subscriber<? super R> actual() {
return actual;
}
@Override
public Object scan(Attr key) {
switch (key) {
case PARENT:
return s;
case ERROR:
return error;
case TERMINATED:
return done && subscribers.isEmpty();
case DELAY_ERROR:
return errorMode != ErrorMode.IMMEDIATE;
case PREFETCH:
return maxConcurrency;
case REQUESTED_FROM_DOWNSTREAM:
return requested;
case BUFFERED:
return subscribers.size();
}
return InnerOperator.super.scan(key);
}
@Override
public void onSubscribe(Subscription s) {
if (Operators.validate(this.s, s)) {
this.s = s;
actual.onSubscribe(this);
s.request(maxConcurrency == Integer.MAX_VALUE ? Long.MAX_VALUE :
maxConcurrency);
}
}
@Override
public void onNext(T t) {
Publisher<? extends R> publisher;
try {
publisher = Objects.requireNonNull(mapper.apply(t), "publisher");
}
catch (Throwable ex) {
onError(Operators.onOperatorError(s, ex, t));
return;
}
MergeSequentialInner<R> inner = new MergeSequentialInner<>(this, prefetch);
if (cancelled) {
return;
}
if (!subscribers.offer(inner)) {
int badSize = subscribers.size();
inner.cancel();
drainAndCancel();
onError(Operators.onOperatorError(s,
new IllegalStateException("Too many subscribers for " +
"fluxMergeSequential on item: " + t +
"; subscribers: " + badSize),
t));
return;
}
if (cancelled) {
return;
}
publisher.subscribe(inner);
if (cancelled) {
inner.cancel();
drainAndCancel();
}
}
@Override
public void onError(Throwable t) {
if (Exceptions.addThrowable(ERROR, this, t)) {
done = true;
drain();
}
else {
Operators.onErrorDropped(t);
}
}
@Override
public void onComplete() {
done = true;
drain();
}
@Override
public void cancel() {
if (cancelled) {
return;
}
cancelled = true;
s.cancel();
drainAndCancel();
}
void drainAndCancel() {
if (WIP.getAndIncrement(this) == 0) {
do {
cancelAll();
}
while (WIP.decrementAndGet(this) != 0);
}
}
void cancelAll() {
MergeSequentialInner<R> inner;
while ((inner = subscribers.poll()) != null) {
inner.cancel();
}
}
@Override
public void request(long n) {
if (Operators.validate(n)) {
Operators.addAndGet(REQUESTED, this, n);
drain();
}
}
void innerNext(MergeSequentialInner<R> inner, R value) {
if (inner.queue().offer(value)) {
drain();
}
else {
inner.cancel();
onError(Operators.onOperatorError(null, Exceptions.failWithOverflow(Exceptions.BACKPRESSURE_ERROR_QUEUE_FULL), value));
}
}
void innerError(MergeSequentialInner<R> inner, Throwable e) {
if (Exceptions.addThrowable(ERROR, this, e)) {
inner.setDone();
if (errorMode != ErrorMode.END) {
s.cancel();
}
drain();
}
else {
Operators.onErrorDropped(e);
}
}
void innerComplete(MergeSequentialInner<R> inner) {
inner.setDone();
drain();
}
void drain() {
if (WIP.getAndIncrement(this) != 0) {
return;
}
int missed = 1;
MergeSequentialInner<R> inner = current;
Subscriber<? super R> a = actual;
ErrorMode em = errorMode;
for (; ; ) {
long r = requested;
long e = 0L;
if (inner == null) {
if (em != ErrorMode.END) {
Throwable ex = error;
if (ex != null) {
cancelAll();
a.onError(ex);
return;
}
}
boolean outerDone = done;
inner = subscribers.poll();
if (outerDone && inner == null) {
Throwable ex = error;
if (ex != null) {
a.onError(ex);
}
else {
a.onComplete();
}
return;
}
if (inner != null) {
current = inner;
}
}
boolean continueNextSource = false;
if (inner != null) {
Queue<R> q = inner.queue();
if (q != null) {
while (e != r) {
if (cancelled) {
cancelAll();
return;
}
if (em == ErrorMode.IMMEDIATE) {
Throwable ex = error;
if (ex != null) {
current = null;
inner.cancel();
cancelAll();
a.onError(ex);
return;
}
}
boolean d = inner.isDone();
R v;
try {
v = q.poll();
}
catch (Throwable ex) {
current = null;
inner.cancel();
ex = Operators.onOperatorError(ex);
cancelAll();
a.onError(ex);
return;
}
boolean empty = v == null;
if (d && empty) {
inner = null;
current = null;
s.request(1);
continueNextSource = true;
break;
}
if (empty) {
break;
}
a.onNext(v);
e++;
inner.requestOne();
}
if (e == r) {
if (cancelled) {
cancelAll();
return;
}
if (em == ErrorMode.IMMEDIATE) {
Throwable ex = error;
if (ex != null) {
current = null;
inner.cancel();
cancelAll();
a.onError(ex);
return;
}
}
boolean d = inner.isDone();
boolean empty = q.isEmpty();
if (d && empty) {
inner = null;
current = null;
s.request(1);
continueNextSource = true;
}
}
}
}
if (e != 0L && r != Long.MAX_VALUE) {
REQUESTED.addAndGet(this, -e);
}
if (continueNextSource) {
continue;
}
missed = WIP.addAndGet(this, -missed);
if (missed == 0) {
break;
}
}
}
}
/**
* Represents the inner flux in a mergeSequential, that has an internal queue to
* hold items while they arrive out of order. The queue is drained as soon as correct
* order can be restored.
* @param <R> the type of objects emitted by the inner flux
*/
static final class MergeSequentialInner<R> implements InnerConsumer<R>{
final MergeSequentialMain<?, R> parent;
final int prefetch;
final int limit;
volatile Queue<R> queue;
volatile Subscription subscription;
static final AtomicReferenceFieldUpdater<MergeSequentialInner, Subscription>
SUBSCRIPTION = AtomicReferenceFieldUpdater.newUpdater(
MergeSequentialInner.class, Subscription.class, "subscription");
volatile boolean done;
long produced;
int fusionMode;
MergeSequentialInner(MergeSequentialMain<?, R> parent, int prefetch) {
this.parent = parent;
this.prefetch = prefetch;
this.limit = prefetch - (prefetch >> 2);
}
@Override
public Object scan(Attr key) {
switch (key) {
case PARENT:
return subscription;
case ACTUAL:
return parent;
case TERMINATED:
return done && (queue == null || queue.isEmpty());
case CANCELLED:
return subscription == Operators.cancelledSubscription();
case BUFFERED:
return queue == null ? 0 : queue.size();
case PREFETCH:
return prefetch;
}
return null;
}
@Override
public void onSubscribe(Subscription s) {
if (Operators.setOnce(SUBSCRIPTION, this, s)) {
if (s instanceof QueueSubscription) {
@SuppressWarnings("unchecked")
QueueSubscription<R> qs = (QueueSubscription<R>) s;
int m = qs.requestFusion(Fuseable.ANY | Fuseable.THREAD_BARRIER);
if (m == Fuseable.SYNC) {
fusionMode = m;
queue = qs;
done = true;
parent.innerComplete(this);
return;
}
if (m == Fuseable.ASYNC) {
fusionMode = m;
queue = qs;
//FIXME could be mutualized in DrainUtils or Operators (+ review other prefetch based operators)
s.request(prefetch == Integer.MAX_VALUE ? Long.MAX_VALUE : prefetch);
return;
}
}
queue = QueueSupplier.<R>get(prefetch).get();
s.request(prefetch == Integer.MAX_VALUE ? Long.MAX_VALUE : prefetch);
}
}
@Override
public void onNext(R t) {
if (fusionMode == Fuseable.NONE) {
parent.innerNext(this, t);
} else {
parent.drain();
}
}
@Override
public void onError(Throwable t) {
parent.innerError(this, t);
}
@Override
public void onComplete() {
parent.innerComplete(this);
}
void requestOne() {
if (fusionMode != Fuseable.SYNC) {
long p = produced + 1;
if (p == limit) {
produced = 0L;
subscription.request(p);
} else {
produced = p;
}
}
}
void cancel() {
Operators.set(SUBSCRIPTION, this, Operators.cancelledSubscription());
}
boolean isDone() {
return done;
}
void setDone() {
this.done = true;
}
Queue<R> queue() {
return queue;
}
}
}