001/**
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018package org.apache.hadoop.hbase.util;
019
020import java.util.concurrent.CompletableFuture;
021import java.util.function.BiConsumer;
022import org.apache.yetus.audience.InterfaceAudience;
023import org.slf4j.Logger;
024import org.slf4j.LoggerFactory;
025
026/**
027 * Helper class for processing futures.
028 */
029@InterfaceAudience.Private
030public final class FutureUtils {
031
032  private static final Logger LOG = LoggerFactory.getLogger(FutureUtils.class);
033
034  private FutureUtils() {
035  }
036
037  /**
038   * This is method is used when you just want to add a listener to the given future. We will call
039   * {@link CompletableFuture#whenComplete(BiConsumer)} to register the {@code action} to the
040   * {@code future}. Ignoring the return value of a Future is considered as a bad practice as it may
041   * suppress exceptions thrown from the code that completes the future, and this method will catch
042   * all the exception thrown from the {@code action} to catch possible code bugs.
043   * <p/>
044   * And the error phone check will always report FutureReturnValueIgnored because every method in
045   * the {@link CompletableFuture} class will return a new {@link CompletableFuture}, so you always
046   * have one future that has not been checked. So we introduce this method and add a suppress
047   * warnings annotation here.
048   */
049  @SuppressWarnings("FutureReturnValueIgnored")
050  public static <T> void addListener(CompletableFuture<T> future,
051      BiConsumer<? super T, ? super Throwable> action) {
052    future.whenComplete((resp, error) -> {
053      try {
054        action.accept(resp, error);
055      } catch (Throwable t) {
056        LOG.error("Unexpected error caught when processing CompletableFuture", t);
057      }
058    });
059  }
060}