/*
 * 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
 *
 *       https://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.CoreSubscriber;
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.annotation.Nullable;
import reactor.util.concurrent.Queues;
import reactor.util.context.Context;

Maps each upstream value into a Publisher and concatenates them into one sequence of items.
Type parameters:
  • <T> – the source value type
  • <R> – the output value type
See Also:
/** * 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 InternalFluxOperator<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(Flux<? extends T> source, Function<? super T, ? extends Publisher<? extends R>> mapper, int maxConcurrency, int prefetch, ErrorMode errorMode) { this(source, mapper, maxConcurrency, prefetch, errorMode, Queues.get(Math.max(prefetch, maxConcurrency))); } //for testing purpose FluxMergeSequential(Flux<? 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 CoreSubscriber<? super T> subscribeOrReturn(CoreSubscriber<? super R> actual) { //for now mergeSequential doesn't support onErrorContinue, so the scalar version shouldn't either if (FluxFlatMap.trySubscribeScalarMap(source, actual, mapper, false, false)) { return null; } return new MergeSequentialMain<T, R>(actual, mapper, maxConcurrency, prefetch, errorMode, queueSupplier); } @Override public Object scanUnsafe(Attr key) { if (key == Attr.RUN_STYLE) return Attr.RunStyle.SYNC; return super.scanUnsafe(key); } static final class MergeSequentialMain<T, R> implements InnerOperator<T, R> {
the mapper giving the inner publisher for each source value
/** 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
/** how many eagerly subscribed inner stream at a time, at most */
final int maxConcurrency;
request size for inner subscribers (size of the inner queues)
/** 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
/** 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 CoreSubscriber<? 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.
/** 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(CoreSubscriber<? 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 final CoreSubscriber<? super R> actual() { return actual; } @Override public Stream<? extends Scannable> inners() { return Stream.of(subscribers.peek()); } @Override @Nullable public Object scanUnsafe(Attr key) { if (key == Attr.PARENT) return s; if (key == Attr.ERROR) return error; if (key == Attr.TERMINATED) return done && subscribers.isEmpty(); if (key == Attr.DELAY_ERROR) return errorMode != ErrorMode.IMMEDIATE; if (key == Attr.PREFETCH) return maxConcurrency; if (key == Attr.REQUESTED_FROM_DOWNSTREAM) return requested; if (key == Attr.BUFFERED) return subscribers.size(); if (key == Attr.RUN_STYLE) return Attr.RunStyle.SYNC; return InnerOperator.super.scanUnsafe(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, actual.currentContext())); 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, actual.currentContext())); 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, actual.currentContext()); } } @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> c = this.current; if (c != null) { c.cancel(); } MergeSequentialInner<R> inner; while ((inner = subscribers.poll()) != null) { inner.cancel(); } } @Override public void request(long n) { if (Operators.validate(n)) { Operators.addCap(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, actual.currentContext())); } } 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, actual.currentContext()); } } 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(); //noinspection ConstantConditions 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, actual.currentContext()); 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.
Type parameters:
  • <R> – the type of objects emitted by the inner flux
/** * 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 = Operators.unboundedOrLimit(prefetch); } @Override public Context currentContext() { return parent.currentContext(); } @Override @Nullable public Object scanUnsafe(Attr key) { if (key == Attr.PARENT) return subscription; if (key == Attr.ACTUAL) return parent; if (key == Attr.TERMINATED) return done && (queue == null || queue.isEmpty()); if (key == Attr.CANCELLED) return subscription == Operators.cancelledSubscription(); if (key == Attr.BUFFERED) return queue == null ? 0 : queue.size(); if (key == Attr.PREFETCH) return prefetch; if (key == Attr.RUN_STYLE) return Attr.RunStyle.SYNC; 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; s.request(Operators.unboundedOrPrefetch(prefetch)); return; } } queue = Queues.<R>get(prefetch).get(); s.request(Operators.unboundedOrPrefetch(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; } } }