content: /*
   * 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.bookkeeper.common.util;
  
  import com.google.common.util.concurrent.ForwardingExecutorService;
  import java.util.Collection;
  import java.util.List;
  import java.util.concurrent.BlockingQueue;
  import java.util.concurrent.Callable;
  import java.util.concurrent.ExecutionException;
  import java.util.concurrent.ExecutorService;
  import java.util.concurrent.Future;
  import java.util.concurrent.RejectedExecutionException;
  import java.util.concurrent.ThreadPoolExecutor;
  import java.util.concurrent.TimeUnit;
  import java.util.concurrent.TimeoutException;
  
  /**
   * Implements {@link ExecutorService} and allows limiting the number of tasks to
   * be scheduled in the thread's queue.
   */
  public class BoundedExecutorService extends ForwardingExecutorService {
      private final BlockingQueue<Runnable> queue;
      private final ThreadPoolExecutor thread;
      private final int maxTasksInQueue;
  
      public BoundedExecutorService(ThreadPoolExecutor thread, int maxTasksInQueue) {
          this.queue = thread.getQueue();
          this.thread = thread;
          this.maxTasksInQueue = maxTasksInQueue;
      }
  
      @Override
      protected ExecutorService delegate() {
          return this.thread;
      }
  
      private void checkQueue(int numberOfTasks) {
          if (maxTasksInQueue > 0 && (queue.size() + numberOfTasks) > maxTasksInQueue) {
              throw new RejectedExecutionException("Queue at limit of " + maxTasksInQueue + " items");
          }
      }
  
      @Override
      public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) throws InterruptedException {
          checkQueue(tasks.size());
          return super.invokeAll(tasks);
      }
  
      @Override
      public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks, long timeout, TimeUnit unit)
              throws InterruptedException {
          checkQueue(tasks.size());
          return super.invokeAll(tasks, timeout, unit);
      }
  
      @Override
      public <T> T invokeAny(Collection<? extends Callable<T>> tasks) throws InterruptedException, ExecutionException {
          checkQueue(tasks.size());
          return super.invokeAny(tasks);
      }
  
      @Override
      public <T> T invokeAny(Collection<? extends Callable<T>> tasks, long timeout, TimeUnit unit)
              throws InterruptedException, ExecutionException, TimeoutException {
          checkQueue(tasks.size());
          return super.invokeAny(tasks, timeout, unit);
      }
  
      @Override
      public void execute(Runnable command) {
          checkQueue(1);
          super.execute(command);
      }
  
      @Override
      public <T> Future<T> submit(Callable<T> task) {
          checkQueue(1);
          return super.submit(task);
      }
  
      @Override
      public Future<?> submit(Runnable task) {
          checkQueue(1);
          return super.submit(task);
      }
  
      @Override
      public <T> Future<T> submit(Runnable task, T result) {
          checkQueue(1);
          return super.submit(task, result);
      }
  }
  