| /* |
| * 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.drill.exec.util.concurrent; |
| |
| import com.google.common.base.Preconditions; |
| import java.util.concurrent.Callable; |
| import java.util.concurrent.ExecutionException; |
| import java.util.concurrent.ExecutorService; |
| import java.util.concurrent.Future; |
| import java.util.concurrent.TimeUnit; |
| import java.util.concurrent.TimeoutException; |
| |
| /** Utility class to enhance the Java {@link ExecutorService} class functionality */ |
| public final class ExecutorServiceUtil { |
| |
| /** |
| * Helper method to submit the callabale task, gets the original future object, and wrap it |
| * in another future object with the ability to decorate the {@link Future#cancel(boolean)} method; |
| * this decorator will block when future cancellation is invoked (and the "mayInterruptIfRunning" |
| * parameter is set to true). |
| * |
| * @param service the executor service |
| * @param callable a callable task |
| * |
| * @return decorated future object upon successful submission |
| * @see {@link ExecutorService#submit(Callable) |
| */ |
| public static <T> Future<T> submit(ExecutorService service, Callable<T> callable) { |
| // Wrap the original callable object |
| CallableTaskWrapper<T> wrapper = new CallableTaskWrapper<T>(callable); |
| // Submit the wrapper object and set the original future object within the wrapper |
| wrapper.setFuture(service.submit(wrapper)); |
| |
| return wrapper; |
| } |
| |
| /** Executor task wrapper to enhance task cancellation behavior */ |
| public static final class CallableTaskWrapper<T> implements Callable<T>, Future<T> { |
| /** Callable object */ |
| private final Callable<T> callableTask; |
| /** Feature object returned after submission of the callback task */ |
| private volatile Future<T> future; |
| /** Captures the callable task execution status */ |
| private volatile STATE state = STATE.NOT_RUNNING; |
| /** Monitor object */ |
| private final Object monitor = new Object(); |
| |
| /** Captures task's execution state */ |
| private enum STATE { |
| NOT_RUNNING, |
| RUNNING, |
| DONE |
| }; |
| |
| /** |
| * CTOR. |
| * @param callableTask original callable task |
| */ |
| public CallableTaskWrapper(Callable<T> callableTask) { |
| this.callableTask = callableTask; |
| Preconditions.checkNotNull(this.callableTask); |
| } |
| |
| /** {@inheritDoc} */ |
| @Override |
| public T call() throws Exception { |
| try { |
| state = STATE.RUNNING; |
| |
| return callableTask.call(); |
| } finally { |
| state = STATE.DONE; |
| |
| // Optimization: no need to notify if the state is not "cancelled" |
| if (isCancelled()) { |
| synchronized (monitor) { |
| monitor.notifyAll(); |
| } |
| } |
| } |
| } |
| |
| /** |
| * This method will block waiting if the callbale thread is still executing and the "mayInterruptIfRunning" |
| * flag is set; this method will return when: |
| * <ul> |
| * <li>The callbale thread is done executing</li> |
| * <li>The current thread got interrupted; no exception will be thrown and instead the interrupted flag will |
| * be set</li> |
| * </ul> |
| * |
| * @see {@link Future#cancel(boolean)} |
| */ |
| @Override |
| public boolean cancel(boolean mayInterruptIfRunning) { |
| try { |
| |
| return future.cancel(mayInterruptIfRunning); |
| } finally { |
| // If this thread wishes immediate completion of the task and was interrupted (because it was still running), |
| // then block this thread till the callable task is done executing. |
| if (mayInterruptIfRunning) { |
| waitTillDone(); |
| } |
| } |
| } |
| |
| /** {@inheritDoc} */ |
| @Override |
| public boolean isCancelled() { |
| // this method could be called from the call() API before the future is set |
| return future != null && future.isCancelled(); |
| } |
| |
| /** |
| * @return true if the task has completed execution |
| */ |
| @Override |
| public boolean isDone() { |
| return state == STATE.DONE; |
| } |
| |
| /** {@inheritDoc} */ |
| @Override |
| public T get() throws InterruptedException, ExecutionException { |
| return future.get(); |
| } |
| |
| /** {@inheritDoc} */ |
| @Override |
| public T get(long timeout, TimeUnit unit) throws InterruptedException, ExecutionException, TimeoutException { |
| return future.get(timeout, unit); |
| } |
| |
| /** |
| * @param feature the feature to set |
| */ |
| public void setFuture(Future<T> feature) { |
| this.future = feature; |
| } |
| |
| private void waitTillDone() { |
| |
| if (isRunning()) { |
| // Save the current interrupted flag and clear it to allow wait operations |
| boolean interrupted = Thread.interrupted(); |
| |
| try { |
| synchronized (monitor) { |
| while (isRunning()) { |
| try { |
| monitor.wait(); |
| } catch (InterruptedException e) { |
| interrupted = true; |
| } |
| } |
| } |
| } finally { |
| if (interrupted) { |
| Thread.currentThread().interrupt(); |
| } |
| } |
| } |
| } |
| |
| private boolean isRunning() { |
| return state == STATE.RUNNING; |
| } |
| } |
| |
| // ---------------------------------------------------------------------------- |
| // Local implementation |
| // ---------------------------------------------------------------------------- |
| |
| /** Disabling object instantiation */ |
| private ExecutorServiceUtil() { |
| |
| } |
| } |