com.google.devtools.build.lib.concurrent.MoreFutures.java Source code

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// Copyright 2014 The Bazel Authors. 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 com.google.devtools.build.lib.concurrent;

import com.google.common.collect.Iterables;
import com.google.common.util.concurrent.FutureCallback;
import com.google.common.util.concurrent.Futures;
import com.google.common.util.concurrent.ListenableFuture;

import java.util.List;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;

import javax.annotation.Nullable;

/**
 * Utility class for working with futures.
 */
public class MoreFutures {

    private MoreFutures() {
    }

    /**
     * Waits for the first one of the following to occur:
     * <ul>
     * <li>All of the given futures complete successfully.
     * <li>One of the given futures has an {@link ExecutionException}. This {@link ExecutionException}
     *   is propagated. (N.B. If multiple futures have {@link ExecutionExceptions}s, one will be
     *   selected non-deterministically.)
     * <li>The calling thread is interrupted. The {@link InterruptedException} is propagated.
     * </ul>
     */
    public static <V> void waitForAllInterruptiblyFailFast(Iterable<? extends Future<? extends V>> futures)
            throws ExecutionException, InterruptedException {
        int numFutures = Iterables.size(futures);
        while (true) {
            int numCompletedFutures = 0;
            for (Future<? extends V> future : futures) {
                try {
                    future.get(1, TimeUnit.MILLISECONDS);
                } catch (TimeoutException te) {
                    continue;
                } catch (ExecutionException ee) {
                    throw ee;
                }
                numCompletedFutures++;
            }
            if (numCompletedFutures == numFutures) {
                return;
            }
        }
    }

    /**
     * Creates a new {@code ListenableFuture} whose value is a list containing the
     * values of all its input futures, if all succeed. If any input fails, the
     * returned future fails. If any of the futures fails, it cancels all the other futures.
     *
     * <p> This method is similar to {@code Futures.allAsList} but additionally it cancels all the
     * futures in case any of them fails.
     */
    public static <V> ListenableFuture<List<V>> allAsListOrCancelAll(
            final Iterable<? extends ListenableFuture<? extends V>> futures) {
        ListenableFuture<List<V>> combinedFuture = Futures.allAsList(futures);
        Futures.addCallback(combinedFuture, new FutureCallback<List<V>>() {
            @Override
            public void onSuccess(@Nullable List<V> vs) {
            }

            /**
             * In case of a failure of any of the futures (that gets propagated to combinedFuture) we
             * cancel all the futures in the list.
             */
            @Override
            public void onFailure(Throwable ignore) {
                for (ListenableFuture<? extends V> future : futures) {
                    future.cancel(true);
                }
            }
        });
        return combinedFuture;
    }
}