test/jdk/java/nio/file/WatchService/LotsOfEntries.java

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/* @test
 * @bug 8330077
 * @summary Tests WatchService behavior with more entries in a watched directory
 *     than the default event limit
 * @library ..
 * @run main/othervm LotsOfEntries 600 fail
 * @run main/othervm -Djdk.nio.file.WatchService.maxEventsPerPoll=invalid LotsOfEntries 600 fail
 * @run main/othervm -Djdk.nio.file.WatchService.maxEventsPerPoll=-5 LotsOfEntries 5 fail
 * @run main/othervm -Djdk.nio.file.WatchService.maxEventsPerPoll=5 LotsOfEntries 5 pass
 * @run main/othervm -Djdk.nio.file.WatchService.maxEventsPerPoll=5 LotsOfEntries 6 fail
 * @run main/othervm -Djdk.nio.file.WatchService.maxEventsPerPoll=700 LotsOfEntries 600 pass
 * @run main/othervm -Djdk.nio.file.WatchService.maxEventsPerPoll=3000000000 LotsOfEntries 600 pass
 */

import java.nio.file.*;
import static java.nio.file.StandardWatchEventKinds.*;
import java.util.*;
import java.util.concurrent.TimeUnit;
import java.util.stream.Collectors;

public class LotsOfEntries {

    static void testCreateLotsOfEntries(Path dir, int numEvents, boolean fail) throws Exception {
        try (WatchService watcher = FileSystems.getDefault().newWatchService()) {
            System.out.format("register %s for events\n", dir);
            WatchKey key = dir.register(watcher, ENTRY_CREATE);

            System.out.format("create %d entries\n", numEvents);
            Set<Path> entries = new HashSet<>();
            for (int i = 0; i < numEvents; i++) {
                Path entry = dir.resolve("entry" + i);
                entries.add(entry);
                Files.createFile(entry);
            }

            // Wait for all events to be signalled - the timeout is long to
            // allow for polling implementations. Since we specifically want to
            // test the maximum number of events buffered for a single
            // WatchKey#pollEvents call, we need to poll on the WatchService
            // repeatedly until all (not just some) events have been signalled.
            System.out.println("poll watcher...");
            WatchKey signalledKey;
            do {
              signalledKey = watcher.poll(10, TimeUnit.SECONDS);
              if (signalledKey != null && signalledKey != key) {
                throw new RuntimeException("Unexpected key returned from poll");
              }
            } while (signalledKey != null);

            if (fail) {
                System.out.println("poll expecting overflow...");
                var events = key.pollEvents();
                if (events.size() != 1) {
                    throw new RuntimeException(
                        "Expected overflow event, got: " + toString(events));
                }
                if (!events.getFirst().kind().equals(OVERFLOW)) {
                    throw new RuntimeException(
                        "Expected overflow event, got: " + toString(events));
                }
            } else {
                System.out.println("poll not expecting overflow...");
                List<WatchEvent<?>> events = key.pollEvents();
                Set<Path> contexts = events.stream()
                    .map(WatchEvent::context)
                    .map(Path.class::cast)
                    .map(entry -> dir.resolve(entry))
                    .collect(Collectors.toSet());
                if (!entries.equals(contexts)) {
                    throw new RuntimeException(
                        "Expected events on: " + entries + ", got: " + toString(events));
                }
            }
        }
    }

    static String toString(List<WatchEvent<?>> events) {
        return events.stream()
            .map(LotsOfEntries::toString)
            .collect(Collectors.joining(", "));
    }

    static String toString(WatchEvent event) {
        return String.format("%s(%d): %s", event.kind(), event.count(), event.context());
    }

    public static void main(String[] args) throws Exception {
        Path dir = TestUtil.createTemporaryDirectory();
        int numEvents = Integer.parseInt(args[0]);
        boolean fail = args[1].equals("fail");
        try {
            testCreateLotsOfEntries(dir, numEvents, fail);
        } finally {
            TestUtil.removeAll(dir);
        }
    }
}