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TM: downloadDirectory refactor how SDK sends concurrent download file requests #3867

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Merged
zoewangg merged 6 commits into from
Mar 30, 2023
Merged

TM: downloadDirectory refactor how SDK sends concurrent download file requests #3867

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143a2bb
Stop polling from the request queue if there are still requests in fl…
zoewangg Mar 28, 2023
90dcea6
Refactor async buffering subscriber
zoewangg Mar 29, 2023
5ec364c
Address feedback
zoewangg Mar 29, 2023
fbe70b9
Improve existing test
zoewangg Mar 29, 2023
ce32b2a
move request to onNext
zoewangg Mar 30, 2023
29da386
Merge branch 'master' into zoewang/tmFixDownloadDirectory
zoewangg Mar 30, 2023
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100 changes: 23 additions & 77 deletions ...r/src/main/java/software/amazon/awssdk/transfer/s3/internal/AsyncBufferingSubscriber.java
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Original file line number Diff line number Diff line change
Expand Up @@ -15,18 +15,14 @@

package software.amazon.awssdk.transfer.s3.internal;

import java.util.Optional;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.function.Function;
import org.reactivestreams.Subscriber;
import org.reactivestreams.Subscription;
import software.amazon.awssdk.annotations.SdkInternalApi;
import software.amazon.awssdk.utils.Logger;
import software.amazon.awssdk.utils.Validate;
import software.amazon.awssdk.utils.async.DemandIgnoringSubscription;
import software.amazon.awssdk.utils.async.StoringSubscriber;

/**
* An implementation of {@link Subscriber} that execute the provided function for every event and limits the number of concurrent
Expand All @@ -41,20 +37,16 @@ public class AsyncBufferingSubscriber<T> implements Subscriber<T> {
private final Function<T, CompletableFuture<?>> consumer;
private final int maxConcurrentExecutions;
private final AtomicInteger numRequestsInFlight;
private final AtomicBoolean isDelivering = new AtomicBoolean(false);
private volatile boolean isStreamingDone;
private volatile boolean upstreamDone;
private Subscription subscription;

private final StoringSubscriber<T> storingSubscriber;

public AsyncBufferingSubscriber(Function<T, CompletableFuture<?>> consumer,
CompletableFuture<Void> returnFuture,
int maxConcurrentExecutions) {
this.returnFuture = returnFuture;
this.consumer = consumer;
this.maxConcurrentExecutions = maxConcurrentExecutions;
this.numRequestsInFlight = new AtomicInteger(0);
this.storingSubscriber = new StoringSubscriber<>(Integer.MAX_VALUE);
}

@Override
Expand All @@ -65,89 +57,43 @@ public void onSubscribe(Subscription subscription) {
subscription.cancel();
return;
}
storingSubscriber.onSubscribe(new DemandIgnoringSubscription(subscription));
this.subscription = subscription;
subscription.request(maxConcurrentExecutions);
}

@Override
public void onNext(T item) {
storingSubscriber.onNext(item);
flushBufferIfNeeded();
}

private void flushBufferIfNeeded() {
if (isDelivering.compareAndSet(false, true)) {
try {
Optional<StoringSubscriber.Event<T>> next = storingSubscriber.peek();
while (numRequestsInFlight.get() < maxConcurrentExecutions) {
if (!next.isPresent()) {
subscription.request(1);
break;
}

switch (next.get().type()) {
case ON_COMPLETE:
handleCompleteEvent();
break;
case ON_ERROR:
handleError(next.get().runtimeError());
break;
case ON_NEXT:
handleOnNext(next.get().value());
break;
default:
handleError(new IllegalStateException("Unknown stored type: " + next.get().type()));
break;
}

next = storingSubscriber.peek();
}
} finally {
isDelivering.set(false);
}
}
}

private void handleOnNext(T item) {
storingSubscriber.poll();

int numberOfRequestInFlight = numRequestsInFlight.incrementAndGet();
log.debug(() -> "Delivering next item, numRequestInFlight=" + numberOfRequestInFlight);

consumer.apply(item).whenComplete((r, t) -> {
numRequestsInFlight.decrementAndGet();
if (!isStreamingDone) {
subscription.request(1);
} else {
flushBufferIfNeeded();
}
});
}

private void handleCompleteEvent() {
if (numRequestsInFlight.get() == 0) {
returnFuture.complete(null);
storingSubscriber.poll();
}
numRequestsInFlight.incrementAndGet();
consumer.apply(item)
.whenComplete((r, t) ->
checkForCompletion(numRequestsInFlight.decrementAndGet()));
}

@Override
public void onError(Throwable t) {
handleError(t);
storingSubscriber.onError(t);
}

private void handleError(Throwable t) {
// Need to complete future exceptionally first to prevent
// accidental successful completion by a concurrent checkForCompletion.
returnFuture.completeExceptionally(t);
storingSubscriber.poll();
upstreamDone = true;
}

@Override
public void onComplete() {
isStreamingDone = true;
storingSubscriber.onComplete();
flushBufferIfNeeded();
upstreamDone = true;
checkForCompletion(numRequestsInFlight.get());
}

private void checkForCompletion(int requestsInFlight) {
if (upstreamDone && requestsInFlight == 0) {
// This could get invoked multiple times, but it doesn't matter
// because future.complete is idempotent.
returnFuture.complete(null);
return;
}

synchronized (this) {
subscription.request(1);
}
}

/**
Expand Down