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Feature/rate limiter publisher #672
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242 changes: 242 additions & 0 deletions
242
rsocket-core/src/main/java/io/rsocket/internal/RateLimitableRequestPublisher.java
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,242 @@ | ||
| /* | ||
| * Copyright 2015-2018 the original author or authors. | ||
| * | ||
| * 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. | ||
| */ | ||
|
|
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| package io.rsocket.internal; | ||
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| import java.util.concurrent.atomic.AtomicIntegerFieldUpdater; | ||
| import javax.annotation.Nullable; | ||
| import org.reactivestreams.Publisher; | ||
| import org.reactivestreams.Subscriber; | ||
| import org.reactivestreams.Subscription; | ||
| import reactor.core.CoreSubscriber; | ||
| import reactor.core.publisher.Flux; | ||
| import reactor.core.publisher.Operators; | ||
|
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| /** */ | ||
| public class RateLimitableRequestPublisher<T> extends Flux<T> implements Subscription { | ||
|
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| private static final int NOT_CANCELED_STATE = 0; | ||
| private static final int CANCELED_STATE = 1; | ||
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| private final Publisher<T> source; | ||
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| private volatile int canceled; | ||
| private static final AtomicIntegerFieldUpdater<RateLimitableRequestPublisher> CANCELED = | ||
| AtomicIntegerFieldUpdater.newUpdater(RateLimitableRequestPublisher.class, "canceled"); | ||
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| private final long prefetch; | ||
| private final long limit; | ||
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| private long externalRequested; // need sync | ||
| private int pendingToFulfil; // need sync since should be checked/zerroed in onNext | ||
| // and increased in request | ||
| private int deliveredElements; // no need to sync since increased zerroed only in | ||
| // the request method | ||
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| private boolean subscribed; | ||
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| private @Nullable Subscription internalSubscription; | ||
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| private RateLimitableRequestPublisher(Publisher<T> source, long prefetch) { | ||
| this.source = source; | ||
| this.prefetch = prefetch; | ||
| this.limit = prefetch == Integer.MAX_VALUE ? Integer.MAX_VALUE : (prefetch - (prefetch >> 2)); | ||
| } | ||
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| public static <T> RateLimitableRequestPublisher<T> wrap(Publisher<T> source, long prefetch) { | ||
| return new RateLimitableRequestPublisher<>(source, prefetch); | ||
| } | ||
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| @Override | ||
| public void subscribe(CoreSubscriber<? super T> destination) { | ||
| synchronized (this) { | ||
| if (subscribed) { | ||
| throw new IllegalStateException("only one subscriber at a time"); | ||
| } | ||
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| subscribed = true; | ||
| } | ||
| final InnerOperator s = new InnerOperator(destination); | ||
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| source.subscribe(s); | ||
| destination.onSubscribe(s); | ||
| } | ||
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| @Override | ||
| public void request(long n) { | ||
| synchronized (this) { | ||
| long requested = externalRequested; | ||
| if (requested == Long.MAX_VALUE) { | ||
| return; | ||
| } | ||
| externalRequested = Operators.addCap(n, requested); | ||
| } | ||
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| requestN(); | ||
| } | ||
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| private void requestN() { | ||
| final long r; | ||
| final Subscription s; | ||
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| synchronized (this) { | ||
| s = internalSubscription; | ||
| if (s == null) { | ||
| return; | ||
| } | ||
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| final long er = externalRequested; | ||
| final long p = prefetch; | ||
| final int pendingFulfil = pendingToFulfil; | ||
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| if (er != Long.MAX_VALUE || p != Integer.MAX_VALUE) { | ||
| // shortcut | ||
| if (pendingFulfil == p) { | ||
| return; | ||
| } | ||
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| r = Math.min(p - pendingFulfil, er); | ||
| if (er != Long.MAX_VALUE) { | ||
| externalRequested -= r; | ||
| } | ||
| if (p != Integer.MAX_VALUE) { | ||
| pendingToFulfil += r; | ||
| } | ||
| } else { | ||
| r = Long.MAX_VALUE; | ||
| } | ||
| } | ||
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| if (r > 0) { | ||
| s.request(r); | ||
| } | ||
| } | ||
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| public void cancel() { | ||
| if (!isCanceled() && CANCELED.compareAndSet(this, NOT_CANCELED_STATE, CANCELED_STATE)) { | ||
| Subscription s; | ||
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| synchronized (this) { | ||
| s = internalSubscription; | ||
| internalSubscription = null; | ||
| subscribed = false; | ||
| } | ||
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| if (s != null) { | ||
| s.cancel(); | ||
| } | ||
| } | ||
| } | ||
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| private boolean isCanceled() { | ||
| return canceled == CANCELED_STATE; | ||
| } | ||
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| private class InnerOperator implements CoreSubscriber<T>, Subscription { | ||
| final Subscriber<? super T> destination; | ||
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| private InnerOperator(Subscriber<? super T> destination) { | ||
| this.destination = destination; | ||
| } | ||
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| @Override | ||
| public void onSubscribe(Subscription s) { | ||
| synchronized (RateLimitableRequestPublisher.this) { | ||
| RateLimitableRequestPublisher.this.internalSubscription = s; | ||
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| if (isCanceled()) { | ||
| s.cancel(); | ||
| subscribed = false; | ||
| RateLimitableRequestPublisher.this.internalSubscription = null; | ||
| } | ||
| } | ||
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| requestN(); | ||
| } | ||
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| @Override | ||
| public void onNext(T t) { | ||
| try { | ||
| destination.onNext(t); | ||
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| if (prefetch == Integer.MAX_VALUE) { | ||
| return; | ||
| } | ||
|
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| final long l = limit; | ||
| int d = deliveredElements + 1; | ||
|
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| if (d == l) { | ||
| d = 0; | ||
| final long r; | ||
| final Subscription s; | ||
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| synchronized (RateLimitableRequestPublisher.this) { | ||
| long er = externalRequested; | ||
| s = internalSubscription; | ||
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| if (s == null) { | ||
| return; | ||
| } | ||
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| if (er >= l) { | ||
| er -= l; | ||
| // keep pendingToFulfil as is since it is eq to prefetch | ||
| r = l; | ||
| } else { | ||
| pendingToFulfil -= l; | ||
| if (er > 0) { | ||
| r = er; | ||
| er = 0; | ||
| pendingToFulfil += r; | ||
| } else { | ||
| r = 0; | ||
| } | ||
| } | ||
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| externalRequested = er; | ||
| } | ||
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| if (r > 0) { | ||
| s.request(r); | ||
| } | ||
| } | ||
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| deliveredElements = d; | ||
| } catch (Throwable e) { | ||
| onError(e); | ||
| } | ||
| } | ||
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| @Override | ||
| public void onError(Throwable t) { | ||
| destination.onError(t); | ||
| } | ||
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| @Override | ||
| public void onComplete() { | ||
| destination.onComplete(); | ||
| } | ||
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| @Override | ||
| public void request(long n) {} | ||
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| @Override | ||
| public void cancel() { | ||
| RateLimitableRequestPublisher.this.cancel(); | ||
| } | ||
| } | ||
| } | ||
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This doesn't appear to match the logic on line 56. Integer vs Long MAX_VALUE. It's hard to intuit whether that's intentional because there are multiple fields. Maybe some comments to clarify what max values are used.