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8331142: Add test for number of loader threads in BasicDirectoryModel
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8331495: Limit BasicDirectoryModel/LoaderThreadCount.java to Windows only

Reviewed-by: mdoerr
Backport-of: b2fb5ea13ba5087411410519213fc953ecc44618
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Andrew Lu committed Jun 17, 2024
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/*
* Copyright (c) 2024, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Objects;
import java.util.concurrent.BrokenBarrierException;
import java.util.concurrent.CyclicBarrier;
import java.util.concurrent.atomic.AtomicReference;
import java.util.stream.LongStream;
import java.util.stream.Stream;

import javax.swing.JFileChooser;

/*
* @test
* @bug 8325179
* @requires os.family == "windows"
* @summary Verifies there's only one BasicDirectoryModel.FilesLoader thread
* at any given moment
* @run main/othervm -Djava.awt.headless=true LoaderThreadCount
*/
public final class LoaderThreadCount extends ThreadGroup {
/** Initial number of files. */
private static final long NUMBER_OF_FILES = 500;

/**
* Number of threads running {@code fileChooser.rescanCurrentDirectory()}.
*/
private static final int NUMBER_OF_THREADS = 5;

/** Number of snapshots with live threads. */
private static final int SNAPSHOTS = 20;

/** The barrier to synchronise scanner threads and capturing live threads. */
private static final CyclicBarrier start = new CyclicBarrier(NUMBER_OF_THREADS + 1);

/** List of scanner threads. */
private static final List<Thread> threads = new ArrayList<>(NUMBER_OF_THREADS);

/**
* Stores an exception caught by any of the threads.
* If more exceptions are caught, they're added as suppressed exceptions.
*/
private static final AtomicReference<Throwable> exception =
new AtomicReference<>();

/**
* Stores an {@code IOException} thrown while removing the files.
*/
private static final AtomicReference<IOException> ioException =
new AtomicReference<>();


public static void main(String[] args) throws Throwable {
try {
// Start the test in its own thread group to catch and handle
// all thrown exceptions, in particular in
// BasicDirectoryModel.FilesLoader which is created by Swing.
ThreadGroup threadGroup = new LoaderThreadCount();
Thread runner = new Thread(threadGroup,
LoaderThreadCount::wrapper,
"Test Runner");
runner.start();
runner.join();
} catch (Throwable throwable) {
handleException(throwable);
}

if (ioException.get() != null) {
System.err.println("An error occurred while removing files:");
ioException.get().printStackTrace();
}

if (exception.get() != null) {
throw exception.get();
}
}

private static void wrapper() {
final long timeStart = System.currentTimeMillis();
try {
runTest(timeStart);
} catch (Throwable throwable) {
handleException(throwable);
} finally {
System.out.printf("Duration: %,d\n",
(System.currentTimeMillis() - timeStart));
}
}

private static void runTest(final long timeStart) throws Throwable {
final Path temp = Files.createDirectory(Paths.get("fileChooser-concurrency-" + timeStart));

try {
createFiles(temp);

final JFileChooser fc = new JFileChooser(temp.toFile());

threads.addAll(Stream.generate(() -> new Thread(new Scanner(fc)))
.limit(NUMBER_OF_THREADS)
.toList());
threads.forEach(Thread::start);

// Create snapshots of live threads
List<Thread[]> threadsCapture =
Stream.generate(LoaderThreadCount::getThreadSnapshot)
.limit(SNAPSHOTS)
.toList();

threads.forEach(Thread::interrupt);

List<Long> loaderCount =
threadsCapture.stream()
.map(ta -> Arrays.stream(ta)
.filter(Objects::nonNull)
.map(Thread::getName)
.filter(tn -> tn.startsWith("Basic L&F File Loading Thread"))
.count())
.filter(c -> c > 0)
.toList();

if (loaderCount.isEmpty()) {
throw new RuntimeException("Invalid results: no loader threads detected");
}

System.out.println("Number of snapshots: " + loaderCount.size());

long ones = loaderCount.stream()
.filter(n -> n == 1)
.count();
long twos = loaderCount.stream()
.filter(n -> n == 2)
.count();
long count = loaderCount.stream()
.filter(n -> n > 2)
.count();
System.out.println("Number of snapshots where number of loader threads:");
System.out.println(" = 1: " + ones);
System.out.println(" = 2: " + twos);
System.out.println(" > 2: " + count);
if (count > 0) {
throw new RuntimeException("Detected " + count + " snapshots "
+ "with several loading threads");
}
} catch (Throwable e) {
threads.forEach(Thread::interrupt);
throw e;
} finally {
deleteFiles(temp);
deleteFile(temp);
}
}

private static Thread[] getThreadSnapshot() {
try {
start.await();
// Allow for the scanner threads to initiate re-scanning
Thread.sleep(10);

Thread[] array = new Thread[Thread.activeCount()];
Thread.currentThread()
.getThreadGroup()
.enumerate(array, false);

// Additional delay between captures
Thread.sleep(500);

return array;
} catch (InterruptedException | BrokenBarrierException e) {
handleException(e);
throw new RuntimeException("getThreadSnapshot is interrupted");
}
}


private LoaderThreadCount() {
super("bdmConcurrency");
}

@Override
public void uncaughtException(Thread t, Throwable e) {
handleException(t, e);
}

private static void handleException(Throwable throwable) {
handleException(Thread.currentThread(), throwable);
}

private static void handleException(final Thread thread,
final Throwable throwable) {
System.err.println("Exception in " + thread.getName() + ": "
+ throwable.getClass()
+ (throwable.getMessage() != null
? ": " + throwable.getMessage()
: ""));
if (!exception.compareAndSet(null, throwable)) {
exception.get().addSuppressed(throwable);
}
threads.stream()
.filter(t -> t != thread)
.forEach(Thread::interrupt);
}


private record Scanner(JFileChooser fileChooser)
implements Runnable {

@Override
public void run() {
try {
do {
start.await();
fileChooser.rescanCurrentDirectory();
} while (!Thread.interrupted());
} catch (InterruptedException | BrokenBarrierException e) {
// Just exit the loop
}
}
}

private static void createFiles(final Path parent) {
LongStream.range(0, LoaderThreadCount.NUMBER_OF_FILES)
.mapToObj(n -> parent.resolve(n + ".file"))
.forEach(LoaderThreadCount::createFile);
}

private static void createFile(final Path file) {
try {
Files.createFile(file);
} catch (IOException e) {
throw new RuntimeException(e);
}
}

private static void deleteFiles(final Path parent) throws IOException {
try (var stream = Files.walk(parent)) {
stream.filter(p -> p != parent)
.forEach(LoaderThreadCount::deleteFile);
}
}

private static void deleteFile(final Path file) {
try {
Files.delete(file);
} catch (IOException e) {
if (!ioException.compareAndSet(null, e)) {
ioException.get().addSuppressed(e);
}
}
}
}

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