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FluxDiscardOnCancel.java
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FluxDiscardOnCancel.java
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/*
* Copyright 2019 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
*
* 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 io.r2dbc.postgresql.util;
import org.reactivestreams.Subscriber;
import org.reactivestreams.Subscription;
import reactor.core.CoreSubscriber;
import reactor.core.publisher.Flux;
import reactor.core.publisher.FluxOperator;
import reactor.core.publisher.Operators;
import reactor.util.Logger;
import reactor.util.Loggers;
import reactor.util.context.Context;
import java.util.concurrent.atomic.AtomicBoolean;
/**
* A decorating operator that replays signals from its source to a {@link Subscriber} and drains the source upon {@link Subscription#cancel() cancel} and drops data signals until termination.
* Draining data is required to complete a particular request/response window and clear the protocol state as client code expects to start a request/response conversation without any previous
* response state.
*/
class FluxDiscardOnCancel<T> extends FluxOperator<T, T> {
private static final Logger logger = Loggers.getLogger(FluxDiscardOnCancel.class);
private final Runnable cancelConsumer;
FluxDiscardOnCancel(Flux<? extends T> source, Runnable cancelConsumer) {
super(source);
this.cancelConsumer = cancelConsumer;
}
@Override
public void subscribe(CoreSubscriber<? super T> actual) {
this.source.subscribe(new FluxDiscardOnCancelSubscriber<>(actual, this.cancelConsumer));
}
static class FluxDiscardOnCancelSubscriber<T> extends AtomicBoolean implements CoreSubscriber<T>, Subscription {
final CoreSubscriber<T> actual;
final Context ctx;
final Runnable cancelConsumer;
Subscription s;
FluxDiscardOnCancelSubscriber(CoreSubscriber<T> actual, Runnable cancelConsumer) {
this.actual = actual;
this.ctx = actual.currentContext();
this.cancelConsumer = cancelConsumer;
}
@Override
public Context currentContext() {
return this.ctx;
}
@Override
public void onSubscribe(Subscription s) {
if (Operators.validate(this.s, s)) {
this.s = s;
this.actual.onSubscribe(this);
}
}
@Override
public void onNext(T t) {
if (this.get()) {
Operators.onDiscard(t, this.ctx);
return;
}
this.actual.onNext(t);
}
@Override
public void onError(Throwable t) {
if (!this.get()) {
this.actual.onError(t);
}
}
@Override
public void onComplete() {
if (!this.get()) {
this.actual.onComplete();
}
}
@Override
public void request(long n) {
this.s.request(n);
}
@Override
public void cancel() {
if (compareAndSet(false, true)) {
if (logger.isDebugEnabled()) {
logger.debug("received cancel signal");
}
try {
this.cancelConsumer.run();
} catch (Exception e) {
Operators.onErrorDropped(e, this.ctx);
}
this.s.request(Long.MAX_VALUE);
}
}
}
}