/*
* Copyright (c) 2011-2018 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
*
* 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.
*/
package reactor.core.publisher;
import java.util.
Objects;
import java.util.concurrent.
Callable;
import java.util.concurrent.atomic.
AtomicReferenceFieldUpdater;
import java.util.function.
Function;
import org.reactivestreams.
Publisher;
import org.reactivestreams.
Subscriber;
import org.reactivestreams.
Subscription;
import reactor.core.
CoreSubscriber;
import reactor.core.
Exceptions;
import reactor.core.
Fuseable.
ConditionalSubscriber;
import reactor.core.publisher.
Operators.
DeferredSubscription;
import reactor.util.
Loggers;
import reactor.util.annotation.
Nullable;
import reactor.util.context.
Context;
/**
* Uses a resource that is lazily generated by a {@link Publisher} for each individual{@link Subscriber},
* while streaming the values from a {@link Publisher} derived from the same resource.
* Whenever the resulting sequence terminates, the relevant {@link Function} generates
* a "cleanup" {@link Publisher} that is invoked but doesn't change the content of the
* main sequence. Instead it just defers the termination (unless it errors, in which case
* the error suppresses the original termination signal).
* <p>
* Note that if the resource supplying {@link Publisher} emits more than one resource, the
* subsequent resources are dropped ({@link Operators#onNextDropped(Object, Context)}). If
* the publisher errors AFTER having emitted one resource, the error is also silently dropped
* ({@link Operators#onErrorDropped(Throwable, Context)}).
*
* @param <T> the value type streamed
* @param <S> the resource type
*/
final class
FluxUsingWhen<T, S> extends
Flux<T> implements
SourceProducer<T> {
final
Publisher<S>
resourceSupplier;
final
Function<? super S, ? extends
Publisher<? extends T>>
resourceClosure;
final
Function<? super S, ? extends
Publisher<?>>
asyncComplete;
final
Function<? super S, ? extends
Publisher<?>>
asyncError;
@
Nullable
final
Function<? super S, ? extends
Publisher<?>>
asyncCancel;
FluxUsingWhen(
Publisher<S>
resourceSupplier,
Function<? super S, ? extends
Publisher<? extends T>>
resourceClosure,
Function<? super S, ? extends
Publisher<?>>
asyncComplete,
Function<? super S, ? extends
Publisher<?>>
asyncError,
@
Nullable Function<? super S, ? extends
Publisher<?>>
asyncCancel) {
this.
resourceSupplier =
Objects.
requireNonNull(
resourceSupplier, "resourceSupplier");
this.
resourceClosure =
Objects.
requireNonNull(
resourceClosure, "resourceClosure");
this.
asyncComplete =
Objects.
requireNonNull(
asyncComplete, "asyncComplete");
this.
asyncError =
Objects.
requireNonNull(
asyncError, "asyncError");
this.
asyncCancel =
asyncCancel;
}
@
Override
@
SuppressWarnings("unchecked")
public void
subscribe(
CoreSubscriber<? super T>
actual) {
if (
resourceSupplier instanceof
Callable) {
try {
Callable<S>
resourceCallable = (
Callable<S>)
resourceSupplier;
S
resource =
resourceCallable.
call();
if (
resource == null) {
Operators.
complete(
actual);
}
else {
Publisher<? extends T>
p =
deriveFluxFromResource(
resource,
resourceClosure);
UsingWhenSubscriber<? super T, S>
subscriber =
prepareSubscriberForResource(
resource,
actual,
asyncComplete,
asyncError,
asyncCancel,
null);
p.
subscribe(
subscriber);
}
}
catch (
Throwable e) {
Operators.
error(
actual,
e);
}
return;
}
//trigger the resource creation and delay the subscription to actual
resourceSupplier.
subscribe(new
ResourceSubscriber(
actual,
resourceClosure,
asyncComplete,
asyncError,
asyncCancel,
resourceSupplier instanceof
Mono));
}
@
Override
public
Object scanUnsafe(
Attr key) {
return null; //no particular key to be represented, still useful in hooks
}
private static <RESOURCE, T>
Publisher<? extends T>
deriveFluxFromResource(
RESOURCE
resource,
Function<? super RESOURCE, ? extends
Publisher<? extends T>>
resourceClosure) {
Publisher<? extends T>
p;
try {
p =
Objects.
requireNonNull(
resourceClosure.
apply(
resource),
"The resourceClosure function returned a null value");
}
catch (
Throwable e) {
p =
Flux.
error(
e);
}
return
p;
}
private static <RESOURCE, T>
UsingWhenSubscriber<? super T, RESOURCE>
prepareSubscriberForResource(
RESOURCE
resource,
CoreSubscriber<? super T>
actual,
Function<? super RESOURCE, ? extends
Publisher<?>>
asyncComplete,
Function<? super RESOURCE, ? extends
Publisher<?>>
asyncError,
@
Nullable Function<? super RESOURCE, ? extends
Publisher<?>>
asyncCancel,
@
Nullable DeferredSubscription arbiter) {
if (
actual instanceof
ConditionalSubscriber) {
@
SuppressWarnings("unchecked")
ConditionalSubscriber<? super T>
conditionalActual = (
ConditionalSubscriber<? super T>)
actual;
return new
UsingWhenConditionalSubscriber<>(
conditionalActual,
resource,
asyncComplete,
asyncError,
asyncCancel,
arbiter);
}
else {
return new
UsingWhenSubscriber<>(
actual,
resource,
asyncComplete,
asyncError,
asyncCancel,
arbiter);
}
}
static class
ResourceSubscriber<S, T> extends
DeferredSubscription
implements
InnerConsumer<S> {
final
CoreSubscriber<? super T>
actual;
final
Function<? super S, ? extends
Publisher<? extends T>>
resourceClosure;
final
Function<? super S, ? extends
Publisher<?>>
asyncComplete;
final
Function<? super S, ? extends
Publisher<?>>
asyncError;
@
Nullable
final
Function<? super S, ? extends
Publisher<?>>
asyncCancel;
final boolean
isMonoSource;
Subscription resourceSubscription;
boolean
resourceProvided;
UsingWhenSubscriber<? super T, S>
closureSubscriber;
ResourceSubscriber(
CoreSubscriber<? super T>
actual,
Function<? super S, ? extends
Publisher<? extends T>>
resourceClosure,
Function<? super S, ? extends
Publisher<?>>
asyncComplete,
Function<? super S, ? extends
Publisher<?>>
asyncError,
@
Nullable Function<? super S, ? extends
Publisher<?>>
asyncCancel,
boolean
isMonoSource) {
this.
actual =
Objects.
requireNonNull(
actual, "actual");
this.
resourceClosure =
Objects.
requireNonNull(
resourceClosure, "resourceClosure");
this.
asyncComplete =
Objects.
requireNonNull(
asyncComplete, "asyncComplete");
this.
asyncError =
Objects.
requireNonNull(
asyncError, "asyncError");
this.
asyncCancel =
asyncCancel;
this.
isMonoSource =
isMonoSource;
}
@
Override
public void
onNext(S
resource) {
if (
resourceProvided) {
Operators.
onNextDropped(
resource,
actual.
currentContext());
return;
}
resourceProvided = true;
final
Publisher<? extends T>
p =
deriveFluxFromResource(
resource,
resourceClosure);
this.
closureSubscriber =
prepareSubscriberForResource(
resource,
this.
actual,
this.
asyncComplete,
this.
asyncError,
this.
asyncCancel,
this);
p.
subscribe(
closureSubscriber);
if (!
isMonoSource) {
resourceSubscription.
cancel();
}
}
@
Override
public
Context currentContext() {
return
actual.
currentContext();
}
@
Override
public void
onError(
Throwable throwable) {
if (
resourceProvided) {
Operators.
onErrorDropped(
throwable,
actual.
currentContext());
return;
}
//even if no resource provided, actual.onSubscribe has been called
//let's immediately complete actual
actual.
onError(
throwable);
}
@
Override
public void
onComplete() {
if (
resourceProvided) {
return;
}
//even if no resource provided, actual.onSubscribe has been called
//let's immediately complete actual
actual.
onComplete();
}
@
Override
public void
onSubscribe(
Subscription s) {
if (
Operators.
validate(this.
resourceSubscription,
s)) {
this.
resourceSubscription =
s;
actual.
onSubscribe(this);
s.
request(
Long.
MAX_VALUE);
}
}
@
Override
public void
cancel() {
if (!
resourceProvided) {
resourceSubscription.
cancel();
super.cancel();
}
else {
Operators.
terminate(
S, this);
if (
closureSubscriber != null) {
closureSubscriber.
cancel();
}
}
}
@
Override
public
Object scanUnsafe(
Attr key) {
if (
key ==
Attr.
PARENT) return
resourceSubscription;
if (
key ==
Attr.
ACTUAL) return
actual;
if (
key ==
Attr.
PREFETCH) return
Integer.
MAX_VALUE;
if (
key ==
Attr.
TERMINATED) return
resourceProvided;
return null;
}
}
static class
UsingWhenSubscriber<T, S> implements
UsingWhenParent<T> {
//state that differs in the different variants
final
CoreSubscriber<? super T>
actual;
volatile
Subscription s;
static final
AtomicReferenceFieldUpdater<
UsingWhenSubscriber,
Subscription>
SUBSCRIPTION =
AtomicReferenceFieldUpdater.
newUpdater(
UsingWhenSubscriber.class,
Subscription.class, "s");
//rest of the state is always the same
final S
resource;
final
Function<? super S, ? extends
Publisher<?>>
asyncComplete;
final
Function<? super S, ? extends
Publisher<?>>
asyncError;
@
Nullable
final
Function<? super S, ? extends
Publisher<?>>
asyncCancel;
@
Nullable
final
DeferredSubscription arbiter;
/**
* Also stores the onComplete terminal state as {@link Exceptions#TERMINATED}
*/
Throwable error;
UsingWhenSubscriber(
CoreSubscriber<? super T>
actual,
S
resource,
Function<? super S, ? extends
Publisher<?>>
asyncComplete,
Function<? super S, ? extends
Publisher<?>>
asyncError,
@
Nullable Function<? super S, ? extends
Publisher<?>>
asyncCancel,
@
Nullable DeferredSubscription arbiter) {
this.
actual =
actual;
this.
resource =
resource;
this.
asyncComplete =
asyncComplete;
this.
asyncError =
asyncError;
this.
asyncCancel =
asyncCancel;
this.
arbiter =
arbiter;
}
@
Override
public
CoreSubscriber<? super T>
actual() {
return this.
actual;
}
@
Nullable
public
Object scanUnsafe(
Attr key) {
if (
key ==
Attr.
TERMINATED) return
error != null;
if (
key ==
Attr.
ERROR) return (
error ==
Exceptions.
TERMINATED) ? null :
error;
if (
key ==
Attr.
CANCELLED) return
s ==
Operators.
cancelledSubscription();
if (
key ==
Attr.
PARENT) return
s;
return
UsingWhenParent.super.scanUnsafe(
key);
}
@
Override
public void
request(long
l) {
if (
Operators.
validate(
l)) {
s.
request(
l);
}
}
@
Override
public void
cancel() {
if (
Operators.
terminate(
SUBSCRIPTION, this)) {
try {
if (
asyncCancel != null) {
Flux.
from(
asyncCancel.
apply(
resource))
.
subscribe(new
CancelInner(this));
}
else {
Flux.
from(
asyncComplete.
apply(
resource))
.
subscribe(new
CancelInner(this));
}
}
catch (
Throwable error) {
Loggers.
getLogger(
FluxUsingWhen.class).
warn("Error generating async resource cleanup during onCancel",
error);
}
}
}
@
Override
public void
onNext(T
t) {
actual.
onNext(
t);
}
@
Override
public void
onError(
Throwable t) {
Publisher<?>
p;
try {
p =
Objects.
requireNonNull(
asyncError.
apply(
resource),
"The asyncError returned a null Publisher");
}
catch (
Throwable e) {
Throwable _e =
Operators.
onOperatorError(
e,
actual.
currentContext());
_e =
Exceptions.
addSuppressed(
_e,
t);
actual.
onError(
_e);
return;
}
p.
subscribe(new
RollbackInner(this,
t));
}
@
Override
public void
onComplete() {
Publisher<?>
p;
try {
p =
Objects.
requireNonNull(
asyncComplete.
apply(
resource),
"The asyncComplete returned a null Publisher");
}
catch (
Throwable e) {
Throwable _e =
Operators.
onOperatorError(
e,
actual.
currentContext());
actual.
onError(
_e);
return;
}
p.
subscribe(new
CommitInner(this));
}
@
Override
public void
deferredComplete() {
this.
error =
Exceptions.
TERMINATED;
this.
actual.
onComplete();
}
@
Override
public void
deferredError(
Throwable error) {
this.
error =
error;
this.
actual.
onError(
error);
}
@
Override
public void
onSubscribe(
Subscription s) {
if (
Operators.
validate(this.
s,
s)) {
this.
s =
s;
if (
arbiter == null) {
actual.
onSubscribe(this);
}
else {
arbiter.
set(
s);
}
}
}
}
static final class
UsingWhenConditionalSubscriber<T, S>
extends
UsingWhenSubscriber<T, S>
implements
ConditionalSubscriber<T> {
final
ConditionalSubscriber<? super T>
actual;
UsingWhenConditionalSubscriber(
ConditionalSubscriber<? super T>
actual,
S
resource,
Function<? super S, ? extends
Publisher<?>>
asyncComplete,
Function<? super S, ? extends
Publisher<?>>
asyncError,
@
Nullable Function<? super S, ? extends
Publisher<?>>
asyncCancel,
@
Nullable DeferredSubscription arbiter) {
super(
actual,
resource,
asyncComplete,
asyncError,
asyncCancel,
arbiter);
this.
actual =
actual;
}
@
Override
public boolean
tryOnNext(T
t) {
return
actual.
tryOnNext(
t);
}
}
static final class
RollbackInner implements
InnerConsumer<
Object> {
final
UsingWhenParent parent;
final
Throwable rollbackCause;
boolean
done;
RollbackInner(
UsingWhenParent ts,
Throwable rollbackCause) {
this.
parent =
ts;
this.
rollbackCause =
rollbackCause;
}
@
Override
public
Context currentContext() {
return
parent.
currentContext();
}
@
Override
public void
onSubscribe(
Subscription s) {
Objects.
requireNonNull(
s, "Subscription cannot be null")
.
request(
Long.
MAX_VALUE);
}
@
Override
public void
onNext(
Object o) {
//NO-OP
}
@
Override
public void
onError(
Throwable e) {
done = true;
RuntimeException rollbackError = new
RuntimeException("Async resource cleanup failed after onError",
e);
parent.
deferredError(
Exceptions.
addSuppressed(
rollbackError,
rollbackCause));
}
@
Override
public void
onComplete() {
done = true;
parent.
deferredError(
rollbackCause);
}
@
Override
public
Object scanUnsafe(
Attr key) {
if (
key ==
Attr.
PARENT) return
parent;
if (
key ==
Attr.
ACTUAL) return
parent.
actual();
if (
key ==
Attr.
ERROR) return
rollbackCause;
if (
key ==
Attr.
TERMINATED) return
done;
return null;
}
}
static final class
CommitInner implements
InnerConsumer<
Object> {
final
UsingWhenParent parent;
boolean
done;
CommitInner(
UsingWhenParent ts) {
this.
parent =
ts;
}
@
Override
public
Context currentContext() {
return
parent.
currentContext();
}
@
Override
public void
onSubscribe(
Subscription s) {
Objects.
requireNonNull(
s, "Subscription cannot be null")
.
request(
Long.
MAX_VALUE);
}
@
Override
public void
onNext(
Object o) {
//NO-OP
}
@
Override
public void
onError(
Throwable e) {
done = true;
Throwable e_ =
Operators.
onOperatorError(
e,
parent.
currentContext());
Throwable commitError = new
RuntimeException("Async resource cleanup failed after onComplete",
e_);
parent.
deferredError(
commitError);
}
@
Override
public void
onComplete() {
done = true;
parent.
deferredComplete();
}
@
Override
public
Object scanUnsafe(
Attr key) {
if (
key ==
Attr.
PARENT) return
parent;
if (
key ==
Attr.
ACTUAL) return
parent.
actual();
if (
key ==
Attr.
TERMINATED) return
done;
return null;
}
}
/**
* Used in the cancel path to still give the generated Publisher access to the Context
*/
static final class
CancelInner implements
InnerConsumer<
Object> {
final
UsingWhenParent parent;
CancelInner(
UsingWhenParent ts) {
this.
parent =
ts;
}
@
Override
public
Context currentContext() {
return
parent.
currentContext();
}
@
Override
public void
onSubscribe(
Subscription s) {
Objects.
requireNonNull(
s, "Subscription cannot be null")
.
request(
Long.
MAX_VALUE);
}
@
Override
public void
onNext(
Object o) {
//NO-OP
}
@
Override
public void
onError(
Throwable e) {
Loggers.
getLogger(
FluxUsingWhen.class).
warn("Async resource cleanup failed after cancel",
e);
}
@
Override
public void
onComplete() {
//NO-OP
}
@
Override
public
Object scanUnsafe(
Attr key) {
if (
key ==
Attr.
PARENT) return
parent;
if (
key ==
Attr.
ACTUAL) return
parent.
actual();
return null;
}
}
private interface
UsingWhenParent<T> extends
InnerOperator<T, T> {
void
deferredComplete();
void
deferredError(
Throwable error);
}
}