keith-turner commented on a change in pull request #402: ACCUMULO-4615: Updated get status for thread safety and with a per-task timeout URL: https://github.com/apache/accumulo/pull/402#discussion_r177162541
########## File path: server/master/src/main/java/org/apache/accumulo/master/TimeoutTaskExecutor.java ########## @@ -0,0 +1,235 @@ +/* + * 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.accumulo.master; + +import java.util.ArrayList; +import java.util.List; +import java.util.Objects; +import java.util.concurrent.ArrayBlockingQueue; +import java.util.concurrent.BlockingQueue; +import java.util.concurrent.Callable; +import java.util.concurrent.ExecutorService; +import java.util.concurrent.Executors; +import java.util.concurrent.Future; +import java.util.concurrent.TimeUnit; +import java.util.concurrent.TimeoutException; + +import javax.annotation.concurrent.NotThreadSafe; + +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +import com.google.common.base.Preconditions; + +/** + * Runs one or more tasks with a timeout per task (instead of a timeout for the entire pool). Uses callbacks to invoke functions on successful, timed out, or + * tasks that error. + * + * This class uses an underlying fixed thread pool to schedule the submitted tasks. Once a task is submitted, the desired end time for the task is recorded and + * used to determine the timeout for the task's associated {@link Future}. + * + * The timeout will not be exact as the start time is recorded prior to submitting the {@link Callable}. This may result in an effective timeout that is + * slightly smaller than expected. The timeout used during initialization should be adjusted accordingly. + * + * The {@link TimeoutTaskExecutor} itself is not a thread-safe class. Only a single thread should submit tasks and complete them. + * + * @param <T> The return type for the corresponding Callable. + * @param <C> The type of Callable submitted to this executor. + */ +@NotThreadSafe +public class TimeoutTaskExecutor<T, C extends Callable<T>> implements AutoCloseable { + + private final static Logger log = LoggerFactory.getLogger(TimeoutTaskExecutor.class); + + private final long timeout; + private final ExecutorService executorService; + private final BlockingQueue<WrappedTask> startedTasks; + private final List<WrappedTask> wrappedTasks; + + private SuccessCallback<T,C> successCallback; + private ExceptionCallback<C> exceptionCallback; + private TimeoutCallback<C> timeoutCallback; + + /** + * Constructs a new TimeoutTaskExecutor that will use the given number of worker threads and timeout. Takes an expected number of Callables to initialize the + * underlying data structures appropriately. + * <p> + * If the expectedNumCallables is sized too small, this executor will block on calls to submit() once the internal queue is full. + * + * @param numThreads The number of threads to use. + * @param timeout The timeout for each task. + * @param expectedNumCallables The expected number of callables you will schedule. Note this is used for an underlying BlockingQueue. If sized too small this will cause blocking + * when calling submit(). + * @throws IllegalArgumentException If numThreads is less than 1 or expectedNumCallables is negative. + */ + public TimeoutTaskExecutor(int numThreads, long timeout, int expectedNumCallables) { + Preconditions.checkArgument(numThreads >= 1, "Number of threads must be at least 1."); + Preconditions.checkArgument(expectedNumCallables >= 0, "The expected number of callables must be non-negative."); + + this.executorService = Executors.newFixedThreadPool(numThreads); + this.startedTasks = new ArrayBlockingQueue<>(expectedNumCallables); + this.timeout = timeout; + this.wrappedTasks = new ArrayList<>(expectedNumCallables); + } + + /** + * Submits a new task to the executor. + * + * @param callable Task to run + */ + public void submit(C callable) { + WrappedTask wt = new WrappedTask(callable); + wt.future = executorService.submit(wt); + wrappedTasks.add(wt); + } + + /** + * Registers the callback to use on successful tasks. + * + * @param successCallback The callback function to invoke on success. + * @throws NullPointerException when a null successCallback is passed in + */ + public void onSuccess(SuccessCallback<T,C> successCallback) { + this.successCallback = Objects.requireNonNull(successCallback, "Must provide a non-null successCallback."); + } + + /** + * Registers the callback to use on tasks that throw exceptions. + * + * @param exceptionCallback The callback function to invoke on exceptions. + * @throws NullPointerException when a null exceptionCallback is passed in + */ + public void onException(ExceptionCallback<C> exceptionCallback) { + this.exceptionCallback = Objects.requireNonNull(exceptionCallback, "Must provide a non-null exceptionCallback."); + } + + /** + * Registers the callback to use on tasks that time out. + * + * @param timeoutCallback The callback function to invoke on timeouts. + * @throws NullPointerException when a null timeoutCallback is passed in + */ + public void onTimeout(TimeoutCallback<C> timeoutCallback) { + this.timeoutCallback = Objects.requireNonNull(timeoutCallback, "Must provide a non-null timeoutCallback."); + } + + /** + * Completes all the current tasks by dispatching to the appropriate callback. + * + * @throws IllegalStateException If all of the callbacks were not registered before calling this method. + * @throws InterruptedException If interrupted while awaiting callable results. + */ + public void complete() throws InterruptedException { + Preconditions.checkState(successCallback != null, "Must set a success callback before completing " + this); + Preconditions.checkState(exceptionCallback != null, "Must set an exception callback before completing " + this); + Preconditions.checkState(timeoutCallback != null, "Must set a timeout callback before completing " + this); + + while (hasUnfinishedTasks()) { + completeTask(startedTasks.take()); + } + + wrappedTasks.clear(); + } + + private boolean hasUnfinishedTasks() { + for (WrappedTask wt : wrappedTasks) { Review comment: `wrappedTasks` is not a sync list so if this method runs in a different thread than calls to `submit()` then changes may not be seen. Could `wrappedTask` be replaced with an AtomicLong? Increment the long before adding to executor and make `call()` decrement in try with finally block. This method could check if the AtomicLong is greater than zero. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org With regards, Apache Git Services
