org.apache.kafka.common.internals.KafkaFutureImpl Maven / Gradle / Ivy
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* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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 org.apache.kafka.common.internals;
import java.util.concurrent.CancellationException;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.CompletionException;
import java.util.concurrent.CompletionStage;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import org.apache.kafka.common.KafkaFuture;
/**
* A flexible future which supports call chaining and other asynchronous programming patterns.
*/
public class KafkaFutureImpl extends KafkaFuture {
private final KafkaCompletableFuture completableFuture;
private final boolean isDependant;
public KafkaFutureImpl() {
this(false, new KafkaCompletableFuture<>());
}
private KafkaFutureImpl(boolean isDependant, KafkaCompletableFuture completableFuture) {
this.isDependant = isDependant;
this.completableFuture = completableFuture;
}
@Override
public CompletionStage toCompletionStage() {
return completableFuture;
}
/**
* Returns a new KafkaFuture that, when this future completes normally, is executed with this
* futures's result as the argument to the supplied function.
*/
@Override
public KafkaFuture thenApply(BaseFunction function) {
CompletableFuture appliedFuture = completableFuture.thenApply(value -> {
try {
return function.apply(value);
} catch (Throwable t) {
if (t instanceof CompletionException) {
// KafkaFuture#thenApply, when the function threw CompletionException should return
// an ExecutionException wrapping a CompletionException wrapping the exception thrown by the
// function. CompletableFuture#thenApply will just return ExecutionException wrapping the
// exception thrown by the function, so we add an extra CompletionException here to
// maintain the KafkaFuture behaviour.
throw new CompletionException(t);
} else {
throw t;
}
}
});
return new KafkaFutureImpl<>(true, toKafkaCompletableFuture(appliedFuture));
}
private static KafkaCompletableFuture toKafkaCompletableFuture(CompletableFuture completableFuture) {
if (completableFuture instanceof KafkaCompletableFuture) {
return (KafkaCompletableFuture) completableFuture;
} else {
final KafkaCompletableFuture result = new KafkaCompletableFuture<>();
completableFuture.whenComplete((x, y) -> {
if (y != null) {
result.kafkaCompleteExceptionally(y);
} else {
result.kafkaComplete(x);
}
});
return result;
}
}
/**
* @see KafkaFutureImpl#thenApply(BaseFunction)
* @deprecated Since Kafka 3.0.
*/
@Deprecated
@Override
public KafkaFuture thenApply(Function function) {
return thenApply((BaseFunction) function);
}
@Override
public KafkaFuture whenComplete(final BiConsumer biConsumer) {
CompletableFuture tCompletableFuture = completableFuture.whenComplete((java.util.function.BiConsumer) (a, b) -> {
try {
biConsumer.accept(a, b);
} catch (Throwable t) {
if (t instanceof CompletionException) {
throw new CompletionException(t);
} else {
throw t;
}
}
});
return new KafkaFutureImpl<>(true, toKafkaCompletableFuture(tCompletableFuture));
}
@Override
public boolean complete(T newValue) {
return completableFuture.kafkaComplete(newValue);
}
@Override
public boolean completeExceptionally(Throwable newException) {
// CompletableFuture#get() always wraps the _cause_ of a CompletionException in ExecutionException
// (which KafkaFuture does not) so wrap CompletionException in an extra one to avoid losing the
// first CompletionException in the exception chain.
return completableFuture.kafkaCompleteExceptionally(
newException instanceof CompletionException ? new CompletionException(newException) : newException);
}
/**
* If not already completed, completes this future with a CancellationException. Dependent
* futures that have not already completed will also complete exceptionally, with a
* CompletionException caused by this CancellationException.
*/
@Override
public boolean cancel(boolean mayInterruptIfRunning) {
return completableFuture.cancel(mayInterruptIfRunning);
}
/**
* We need to deal with differences between KafkaFuture's historic API and the API of CompletableFuture:
* CompletableFuture#get() does not wrap CancellationException in ExecutionException (nor does KafkaFuture).
* CompletableFuture#get() always wraps the _cause_ of a CompletionException in ExecutionException
* (which KafkaFuture does not).
*
* The semantics for KafkaFuture are that all exceptional completions of the future (via #completeExceptionally()
* or exceptions from dependants) manifest as ExecutionException, as observed via both get() and getNow().
*/
private void maybeThrowCancellationException(Throwable cause) {
if (cause instanceof CancellationException) {
throw (CancellationException) cause;
}
}
/**
* Waits if necessary for this future to complete, and then returns its result.
*/
@Override
public T get() throws InterruptedException, ExecutionException {
try {
return completableFuture.get();
} catch (ExecutionException e) {
maybeThrowCancellationException(e.getCause());
throw e;
}
}
/**
* Waits if necessary for at most the given time for this future to complete, and then returns
* its result, if available.
*/
@Override
public T get(long timeout, TimeUnit unit) throws InterruptedException, ExecutionException,
TimeoutException {
try {
return completableFuture.get(timeout, unit);
} catch (ExecutionException e) {
maybeThrowCancellationException(e.getCause());
throw e;
}
}
/**
* Returns the result value (or throws any encountered exception) if completed, else returns
* the given valueIfAbsent.
*/
@Override
public T getNow(T valueIfAbsent) throws ExecutionException {
try {
return completableFuture.getNow(valueIfAbsent);
} catch (CompletionException e) {
maybeThrowCancellationException(e.getCause());
// Note, unlike CompletableFuture#get() which throws ExecutionException, CompletableFuture#getNow()
// throws CompletionException, thus needs rewrapping to conform to KafkaFuture API,
// where KafkaFuture#getNow() throws ExecutionException.
throw new ExecutionException(e.getCause());
}
}
/**
* Returns true if this CompletableFuture was cancelled before it completed normally.
*/
@Override
public boolean isCancelled() {
if (isDependant) {
// Having isCancelled() for a dependent future just return
// CompletableFuture.isCancelled() would break the historical KafkaFuture behaviour because
// CompletableFuture#isCancelled() just checks for the exception being CancellationException
// whereas it will be a CompletionException wrapping a CancellationException
// due needing to compensate for CompletableFuture's CompletionException unwrapping
// shenanigans in other methods.
try {
completableFuture.getNow(null);
return false;
} catch (Exception e) {
return e instanceof CompletionException
&& e.getCause() instanceof CancellationException;
}
} else {
return completableFuture.isCancelled();
}
}
/**
* Returns true if this CompletableFuture completed exceptionally, in any way.
*/
@Override
public boolean isCompletedExceptionally() {
return completableFuture.isCompletedExceptionally();
}
/**
* Returns true if completed in any fashion: normally, exceptionally, or via cancellation.
*/
@Override
public boolean isDone() {
return completableFuture.isDone();
}
@Override
public String toString() {
T value = null;
Throwable exception = null;
try {
value = completableFuture.getNow(null);
} catch (CompletionException e) {
exception = e.getCause();
} catch (Exception e) {
exception = e;
}
return String.format("KafkaFuture{value=%s,exception=%s,done=%b}", value, exception, exception != null || value != null);
}
}
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