utils/misc/src/main/java/org/onlab/util/BlockingAwareFuture.java

/*
 * Copyright 2017-present Open Networking Laboratory
 *
 * 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 org.onlab.util;

import java.util.concurrent.CompletableFuture;
import java.util.concurrent.CompletionStage;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Executor;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.function.BiConsumer;
import java.util.function.BiFunction;
import java.util.function.Consumer;
import java.util.function.Function;

/**
 * A {@link CompletableFuture} that tracks whether the future or one of its descendants has been blocked on
 * a {@link CompletableFuture#get()} or {@link CompletableFuture#join()} call.
 */
public class BlockingAwareFuture<T> extends CompletableFuture<T> {
    private final AtomicBoolean blocked;

    public BlockingAwareFuture() {
        this(new AtomicBoolean());
    }

    private BlockingAwareFuture(AtomicBoolean blocked) {
        this.blocked = blocked;
    }

    /**
     * Returns a boolean indicating whether the future is blocked.
     *
     * @return indicates whether the future is blocked
     */
    public boolean isBlocked() {
        return blocked.get();
    }

    @Override
    public T get() throws InterruptedException, ExecutionException {
        blocked.set(true);
        try {
            return super.get();
        } finally {
            blocked.set(false);
        }
    }

    @Override
    public T get(long timeout, TimeUnit unit) throws InterruptedException, ExecutionException, TimeoutException {
        blocked.set(true);
        try {
            return super.get(timeout, unit);
        } finally {
            blocked.set(false);
        }
    }

    @Override
    public synchronized T join() {
        blocked.set(true);
        try {
            return super.join();
        } finally {
            blocked.set(false);
        }
    }

    /**
     * Wraps the given future in a new blockable future.
     *
     * @param future the future to wrap
     * @param <U> the future value type
     * @return a new blockable future
     */
    private <U> CompletableFuture<U> wrap(CompletableFuture<U> future) {
        BlockingAwareFuture<U> blockingFuture = new BlockingAwareFuture<U>(blocked);
        future.whenComplete((result, error) -> {
            if (error == null) {
                blockingFuture.complete(result);
            } else {
                blockingFuture.completeExceptionally(error);
            }
        });
        return blockingFuture;
    }

    @Override
    public <U> CompletableFuture<U> thenApply(Function<? super T, ? extends U> fn) {
        return wrap(super.thenApply(fn));
    }

    @Override
    public <U> CompletableFuture<U> thenApplyAsync(Function<? super T, ? extends U> fn) {
        return wrap(super.thenApplyAsync(fn));
    }

    @Override
    public <U> CompletableFuture<U> thenApplyAsync(Function<? super T, ? extends U> fn, Executor executor) {
        return wrap(super.thenApplyAsync(fn, executor));
    }

    @Override
    public CompletableFuture<Void> thenAccept(Consumer<? super T> action) {
        return wrap(super.thenAccept(action));
    }

    @Override
    public CompletableFuture<Void> thenAcceptAsync(Consumer<? super T> action) {
        return wrap(super.thenAcceptAsync(action));
    }

    @Override
    public CompletableFuture<Void> thenAcceptAsync(Consumer<? super T> action, Executor executor) {
        return wrap(super.thenAcceptAsync(action, executor));
    }

    @Override
    public CompletableFuture<Void> thenRun(Runnable action) {
        return wrap(super.thenRun(action));
    }

    @Override
    public CompletableFuture<Void> thenRunAsync(Runnable action) {
        return wrap(super.thenRunAsync(action));
    }

    @Override
    public CompletableFuture<Void> thenRunAsync(Runnable action, Executor executor) {
        return wrap(super.thenRunAsync(action, executor));
    }

    @Override
    public <U, V> CompletableFuture<V> thenCombine(
            CompletionStage<? extends U> other, BiFunction<? super T, ? super U, ? extends V> fn) {
        return wrap(super.thenCombine(other, fn));
    }

    @Override
    public <U, V> CompletableFuture<V> thenCombineAsync(
            CompletionStage<? extends U> other, BiFunction<? super T, ? super U, ? extends V> fn) {
        return wrap(super.thenCombineAsync(other, fn));
    }

    @Override
    public <U, V> CompletableFuture<V> thenCombineAsync(
            CompletionStage<? extends U> other, BiFunction<? super T, ? super U, ? extends V> fn, Executor executor) {
        return wrap(super.thenCombineAsync(other, fn, executor));
    }

    @Override
    public <U> CompletableFuture<Void> thenAcceptBoth(
            CompletionStage<? extends U> other, BiConsumer<? super T, ? super U> action) {
        return wrap(super.thenAcceptBoth(other, action));
    }

    @Override
    public <U> CompletableFuture<Void> thenAcceptBothAsync(
            CompletionStage<? extends U> other, BiConsumer<? super T, ? super U> action) {
        return wrap(super.thenAcceptBothAsync(other, action));
    }

    @Override
    public <U> CompletableFuture<Void> thenAcceptBothAsync(
            CompletionStage<? extends U> other, BiConsumer<? super T, ? super U> action, Executor executor) {
        return wrap(super.thenAcceptBothAsync(other, action, executor));
    }

    @Override
    public CompletableFuture<Void> runAfterBoth(CompletionStage<?> other, Runnable action) {
        return wrap(super.runAfterBoth(other, action));
    }

    @Override
    public CompletableFuture<Void> runAfterBothAsync(CompletionStage<?> other, Runnable action) {
        return wrap(super.runAfterBothAsync(other, action));
    }

    @Override
    public CompletableFuture<Void> runAfterBothAsync(CompletionStage<?> other, Runnable action, Executor executor) {
        return wrap(super.runAfterBothAsync(other, action, executor));
    }

    @Override
    public <U> CompletableFuture<U> applyToEither(CompletionStage<? extends T> other, Function<? super T, U> fn) {
        return wrap(super.applyToEither(other, fn));
    }

    @Override
    public <U> CompletableFuture<U> applyToEitherAsync(CompletionStage<? extends T> other, Function<? super T, U> fn) {
        return wrap(super.applyToEitherAsync(other, fn));
    }

    @Override
    public <U> CompletableFuture<U> applyToEitherAsync(
            CompletionStage<? extends T> other, Function<? super T, U> fn, Executor executor) {
        return wrap(super.applyToEitherAsync(other, fn, executor));
    }

    @Override
    public CompletableFuture<Void> acceptEither(CompletionStage<? extends T> other, Consumer<? super T> action) {
        return wrap(super.acceptEither(other, action));
    }

    @Override
    public CompletableFuture<Void> acceptEitherAsync(CompletionStage<? extends T> other, Consumer<? super T> action) {
        return wrap(super.acceptEitherAsync(other, action));
    }

    @Override
    public CompletableFuture<Void> acceptEitherAsync(
            CompletionStage<? extends T> other, Consumer<? super T> action, Executor executor) {
        return wrap(super.acceptEitherAsync(other, action, executor));
    }

    @Override
    public CompletableFuture<Void> runAfterEither(CompletionStage<?> other, Runnable action) {
        return wrap(super.runAfterEither(other, action));
    }

    @Override
    public CompletableFuture<Void> runAfterEitherAsync(CompletionStage<?> other, Runnable action) {
        return wrap(super.runAfterEitherAsync(other, action));
    }

    @Override
    public CompletableFuture<Void> runAfterEitherAsync(CompletionStage<?> other, Runnable action, Executor executor) {
        return wrap(super.runAfterEitherAsync(other, action, executor));
    }

    @Override
    public <U> CompletableFuture<U> thenCompose(Function<? super T, ? extends CompletionStage<U>> fn) {
        return wrap(super.thenCompose(fn));
    }

    @Override
    public <U> CompletableFuture<U> thenComposeAsync(Function<? super T, ? extends CompletionStage<U>> fn) {
        return wrap(super.thenComposeAsync(fn));
    }

    @Override
    public <U> CompletableFuture<U> thenComposeAsync(
            Function<? super T, ? extends CompletionStage<U>> fn, Executor executor) {
        return wrap(super.thenComposeAsync(fn, executor));
    }

    @Override
    public CompletableFuture<T> whenComplete(BiConsumer<? super T, ? super Throwable> action) {
        return wrap(super.whenComplete(action));
    }

    @Override
    public CompletableFuture<T> whenCompleteAsync(BiConsumer<? super T, ? super Throwable> action) {
        return wrap(super.whenCompleteAsync(action));
    }

    @Override
    public CompletableFuture<T> whenCompleteAsync(BiConsumer<? super T, ? super Throwable> action, Executor executor) {
        return wrap(super.whenCompleteAsync(action, executor));
    }

    @Override
    public <U> CompletableFuture<U> handle(BiFunction<? super T, Throwable, ? extends U> fn) {
        return wrap(super.handle(fn));
    }

    @Override
    public <U> CompletableFuture<U> handleAsync(BiFunction<? super T, Throwable, ? extends U> fn) {
        return wrap(super.handleAsync(fn));
    }

    @Override
    public <U> CompletableFuture<U> handleAsync(BiFunction<? super T, Throwable, ? extends U> fn, Executor executor) {
        return wrap(super.handleAsync(fn, executor));
    }
}