com.twitter.nodes.utils.Futures.java Source code

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Here is the source code for com.twitter.nodes.utils.Futures.java

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/**
 * Copyright 2016 Twitter, Inc.
 * 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.twitter.nodes.utils;

import java.util.List;
import java.util.Map;

import scala.Tuple2;

import com.google.common.base.Preconditions;
import com.google.common.collect.Lists;
import com.google.common.collect.Maps;

import com.twitter.util.Await;
import com.twitter.util.Function;
import com.twitter.util.Function0;
import com.twitter.util.Future;
import com.twitter.util.Throw;
import com.twitter.util.Throwables;

/**
 * Some utility functions related to Future handle
 */
public final class Futures {
    private Futures() {
    }

    /**
     * Check if a future has completed with success
     */
    public static boolean completedWithSuccess(Future<?> future) {
        try {
            return future.isDefined() && Await.result(future.liftToTry()).isReturn();
        } catch (Exception e) {
            return com.twitter.util.Throwables.unchecked(e);
        }
    }

    /**
     * Check if a future has completed with failure
     */
    public static boolean completedWithFailure(Future<?> future) {
        try {
            return future.isDefined() && Await.result(future.liftToTry()).isThrow();
        } catch (Exception e) {
            return com.twitter.util.Throwables.unchecked(e);
        }
    }

    public static Throwable getException(Future future) {
        Preconditions.checkState(completedWithFailure(future));
        return ((Throw) future.poll().get()).e();
    }

    /**
     * Wait for a map of futures and return a future of map, with the keys mapping to the value
     * returned from corresponding futures.
     */
    public static <K, V> Future<Map<K, V>> collect(final Map<K, Future<V>> futures) {
        try {
            List<Future<Tuple2<K, V>>> entries = Lists.newArrayListWithCapacity(futures.size());
            for (final Map.Entry<K, Future<V>> entry : futures.entrySet()) {
                entries.add(map(entry.getValue(), new Function0<Tuple2<K, V>>() {
                    public Tuple2<K, V> apply() {
                        try {
                            return scala.Tuple2$.MODULE$.apply(entry.getKey(), Await.result(entry.getValue()));
                        } catch (Exception e) {
                            return Throwables.unchecked(e);
                        }
                    }
                }));
            }

            final Future<List<Tuple2<K, V>>> listFuture = Future.collect(entries);

            return map(listFuture, new Function0<Map<K, V>>() {
                public Map<K, V> apply() {
                    Map<K, V> result = Maps.newHashMapWithExpectedSize(futures.size());
                    try {
                        for (Tuple2<K, V> pair : Await.result(listFuture)) {
                            result.put(pair._1(), pair._2());
                        }
                        return result;
                    } catch (Exception e) {
                        return Throwables.unchecked(e);
                    }
                }
            });
        } catch (Exception e) {
            return Throwables.unchecked(e);
        }
    }

    private static <A, R> Future<R> map(final Future<A> a, final Function0<R> f) {
        return a.map(new Function<A, R>() {
            public R apply(A unused) {
                return f.apply();
            }
        });
    }
}