vrozov commented on a change in pull request #1333: DRILL-6410: Memory leak in Parquet Reader during cancellation URL: https://github.com/apache/drill/pull/1333#discussion_r203566491
########## File path: exec/java-exec/src/main/java/org/apache/drill/exec/util/ExecutableTasksLatch.java ########## @@ -0,0 +1,255 @@ +/* + * 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; + +import java.util.Collection; +import java.util.LinkedList; +import java.util.Queue; +import java.util.concurrent.Callable; +import java.util.concurrent.ExecutionException; +import java.util.concurrent.ExecutorService; +import java.util.concurrent.ThreadPoolExecutor; +import java.util.concurrent.atomic.AtomicInteger; +import java.util.concurrent.atomic.AtomicReference; +import java.util.concurrent.locks.LockSupport; +import java.util.function.BooleanSupplier; + +import org.apache.drill.exec.testing.CountDownLatchInjection; +import org.apache.drill.exec.testing.NoOpControlsInjector; + +import com.google.common.base.Preconditions; +import com.google.common.collect.ImmutableList; + +/** + * A wrapper class around {@linkplain ExecutorService an execution service} that allows a thread that instantiated an + * instance of the class to wait for a submitted task to complete (either successfully or unsuccessfully) or to wait for + * all submitted tasks to complete. + * @param <C> type of tasks to execute. <tt>C</tt> must extend {@linkplain Callable}{@literal <Void>} + */ +public class ExecutableTasksLatch<C extends Callable<Void>> { + private static final org.slf4j.Logger logger = org.slf4j.LoggerFactory.getLogger(ExecutableTasksLatch.class); + + /** + * An interface that class {@literal <C>} may optionally implement to receive a callback when a submitted for execution + * task starts or finishes. + */ + public interface Notifiable { + /** + * Notify a task that it is assigned to a thread for execution + */ + void started(); + + /** + * A callback in case a task is considered to be successfully completed (not cancelled). + */ + void finished(); + } + + private final ExecutorService executor; + private final Thread thread; + private final AtomicInteger count; + private final Queue<ExecutableTask<C>> executableTasks; + private final CountDownLatchInjection testCountDownLatch; + + /** + * Constructs an instance of <tt>ExecutableTasksLatch</tt>. A thread where construction is done becomes the waiting + * thread. + * @param executor instance of {@linkplain ExecutorService execution service} to wrap + * @param testCountDownLatch optional {@linkplain CountDownLatchInjection} + */ + public ExecutableTasksLatch(ExecutorService executor, CountDownLatchInjection testCountDownLatch) { + this.executor = executor; + thread = Thread.currentThread(); + count = new AtomicInteger(); + executableTasks = new LinkedList<>(); + this.testCountDownLatch = testCountDownLatch == null ? NoOpControlsInjector.LATCH : testCountDownLatch; + } + + /** + * Waits for an earliest submitted task to complete and removes task from a collection of known tasks. + * @throws ExecutionException if task threw an Exception during execution + * @throws InterruptedException if wait is interrupted + */ + public void take() throws ExecutionException, InterruptedException { + final ExecutableTask<C> task = executableTasks.peek(); + Preconditions.checkState(task != null, "No tasks are scheduled for execution"); + while (ExecutableTask.State.COMPLETING.compareTo(task.state.get()) > 0) { + if (Thread.interrupted()) { + throw new InterruptedException(); + } + LockSupport.park(); + } + executableTasks.remove(); + while (ExecutableTask.State.COMPLETING.compareTo(task.state.get()) == 0) { + Thread.yield(); + } + + if (task.exception != null) { + throw task.exception; + } + } + + /** + * @return immutable collection of submitted for execution tasks that are not yet taken from + * the {@linkplain ExecutableTasksLatch} + */ + public Collection<ExecutableTask<C>> getExecutableTasks() { + return ImmutableList.copyOf(executableTasks); + } + + /** + * submits a task for execution by {@linkplain ExecutorService} + * @param callable task to execute + * @return newly created instance of {@linkplain ExecutableTask} + */ + public ExecutableTask<C> execute(C callable) { + ExecutableTasksLatch.ExecutableTask<C> task = new ExecutableTasksLatch.ExecutableTask<>(callable, this); + executor.execute(task); + count.getAndIncrement(); + if (!executableTasks.add(task)) { + task.cancel(true); + throw new IllegalStateException(); + } + return task; + } + + /** + * Wait for completion of all tasks (cancelling them if cancel returns true) + * @param cancel BooleanSupplier that should return <tt>true</tt> when tasks cancellation is requested + */ + public void await(BooleanSupplier cancel) { + Preconditions.checkState(Thread.currentThread() == thread, + String.format("%s can be awaited only from the %s thread", getClass().getSimpleName(), thread.getName())); + boolean cancelled = false; + while (count.get() > 0) { + if (!cancelled && cancel.getAsBoolean()) { + executableTasks.forEach(task -> task.cancel(true)); + cancelled = true; + } else { + LockSupport.park(); + } + } + } + + /** + * Helper class to wrap {@linkplain Callable}{@literal <Void>} with cancellation and waiting for completion support + * + */ + public static final class ExecutableTask<C extends Callable<Void>> implements Runnable { Review comment: Please see my comment for `ExecutableTasksLatch.await()`. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. 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