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MultiBufferWithTimeoutOp.java
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MultiBufferWithTimeoutOp.java
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package io.smallrye.mutiny.operators.multi;
import java.time.Duration;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.concurrent.RejectedExecutionException;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicLong;
import java.util.function.Supplier;
import org.reactivestreams.Subscription;
import io.smallrye.mutiny.Multi;
import io.smallrye.mutiny.helpers.ParameterValidation;
import io.smallrye.mutiny.helpers.Subscriptions;
import io.smallrye.mutiny.infrastructure.Infrastructure;
import io.smallrye.mutiny.subscription.BackPressureFailure;
import io.smallrye.mutiny.subscription.MultiSubscriber;
import io.smallrye.mutiny.subscription.SerializedSubscriber;
/**
* Buffers items from upstream for a given duration and emits the <em>groups</em> as a single item downstream.
* If the amount of accumulated reach the given size before the timeout, the group is emitted.
* This implementation uses {@link java.util.ArrayList} and so emits {@link List}.
*
* @param <T> the type of item from upstream
*/
public final class MultiBufferWithTimeoutOp<T> extends AbstractMultiOperator<T, List<T>> {
private final int size;
private final Supplier<List<T>> supplier;
private final ScheduledExecutorService scheduler;
private final Duration timeout;
public MultiBufferWithTimeoutOp(Multi<T> upstream,
int size,
Duration timeout,
ScheduledExecutorService scheduler) {
super(upstream);
this.timeout = ParameterValidation.validate(timeout, "timeout");
this.size = ParameterValidation.positive(size, "size");
this.scheduler = ParameterValidation.nonNull(scheduler, "scheduler");
this.supplier = () -> {
if (size < Integer.MAX_VALUE) {
// Not used yet, on the roadmap.
return new ArrayList<>(size);
} else {
return new ArrayList<>();
}
};
}
@Override
public void subscribe(MultiSubscriber<? super List<T>> downstream) {
MultiBufferWithTimeoutProcessor<T> subscriber = new MultiBufferWithTimeoutProcessor<>(
new SerializedSubscriber<>(downstream), size, timeout, scheduler, supplier);
upstream.subscribe().withSubscriber(subscriber);
}
static class MultiBufferWithTimeoutProcessor<T> extends MultiOperatorProcessor<T, List<T>> {
private static final int RUNNING = 0;
private static final int SUCCEED = 1;
private static final int FAILED = 2;
private static final int CANCELLED = 3;
private final int size;
private final Duration duration;
private final ScheduledExecutorService executor;
private final Supplier<List<T>> supplier;
private final Runnable flush;
private final AtomicInteger terminated = new AtomicInteger(RUNNING);
private final AtomicLong requested = new AtomicLong();
private final AtomicInteger index = new AtomicInteger();
private List<T> current;
private ScheduledFuture<?> task;
MultiBufferWithTimeoutProcessor(MultiSubscriber<? super List<T>> downstream, int size, Duration timeout,
ScheduledExecutorService executor, Supplier<List<T>> supplier) {
super(downstream);
this.duration = timeout;
this.executor = executor;
this.supplier = supplier;
this.size = size;
this.flush = () -> {
if (terminated.get() == RUNNING) {
int index;
for (;;) {
index = this.index.get();
if (index == 0) {
return;
}
if (this.index.compareAndSet(index, 0)) {
break;
}
}
flushCallback();
}
};
}
private void doOnSubscribe() {
current = supplier.get();
}
void nextCallback(T value) {
synchronized (this) {
if (current == null) {
current = supplier.get();
}
current.add(value);
}
}
private void flushCallback() {
List<T> cur;
boolean flush = false;
synchronized (this) {
if (current != null) {
cur = new ArrayList<>(current);
} else {
cur = Collections.emptyList();
}
if (!cur.isEmpty()) {
current = supplier.get();
flush = true;
}
}
if (flush) {
long req = requested.get();
MultiSubscriber<? super List<T>> subscriber = downstream;
if (req != 0L) {
if (req != Long.MAX_VALUE) {
long next;
for (;;) {
next = req - 1;
if (requested.compareAndSet(req, next)) {
subscriber.onItem(cur);
return;
}
req = requested.get();
if (req <= 0L) {
break;
}
}
} else {
subscriber.onItem(cur);
return;
}
}
cancel();
subscriber.onFailure(new BackPressureFailure("Cannot emit item due to lack of requests"));
}
}
@Override
public void onItem(final T value) {
int index;
for (;;) {
index = this.index.get() + 1;
if (this.index.compareAndSet(index - 1, index)) {
break;
}
}
if (index == 1) {
try {
task = executor.schedule(flush, duration.toMillis(), TimeUnit.MILLISECONDS);
} catch (RejectedExecutionException rejected) {
onFailure(rejected);
return;
}
}
nextCallback(value);
if (this.index.get() % size == 0) {
this.index.lazySet(0);
if (task != null) {
task.cancel(false);
task = null;
}
flushCallback();
}
}
void checkedComplete() {
try {
flushCallback();
} finally {
super.onCompletion();
}
}
@Override
public void request(long n) {
if (n > 0) {
Subscriptions.add(requested, n);
if (terminated.get() != RUNNING) {
return;
}
if (size == Integer.MAX_VALUE || n == Long.MAX_VALUE) {
super.request(Long.MAX_VALUE);
} else {
super.request(Subscriptions.multiply(n, size));
}
}
}
@Override
public void onCompletion() {
if (terminated.compareAndSet(RUNNING, SUCCEED)) {
if (task != null) {
task.cancel(true);
task = null;
}
checkedComplete();
}
}
@Override
public void onFailure(Throwable throwable) {
if (terminated.compareAndSet(RUNNING, FAILED)) {
synchronized (this) {
if (current != null) {
current.clear();
current = null;
}
}
super.onFailure(throwable);
} else {
Infrastructure.handleDroppedException(throwable);
}
}
@Override
public void onSubscribe(Subscription subscription) {
if (compareAndSetUpstreamSubscription(null, subscription)) {
doOnSubscribe();
downstream.onSubscribe(this);
} else {
subscription.cancel();
}
}
@Override
public void cancel() {
if (terminated.compareAndSet(RUNNING, CANCELLED)) {
super.cancel();
List<T> cur = current;
if (cur != null) {
cur.clear();
}
}
}
}
}