/*
* Copyright 2015 the original author or authors.
*
* Licensed 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.gradle.internal.filewatch.jdk7;
import com.google.common.base.Throwables;
import com.google.common.util.concurrent.FutureCallback;
import com.google.common.util.concurrent.Futures;
import com.google.common.util.concurrent.ListenableFuture;
import com.google.common.util.concurrent.ListeningExecutorService;
import org.gradle.api.Action;
import org.gradle.api.internal.file.FileSystemSubset;
import org.gradle.internal.filewatch.FileWatcher;
import org.gradle.internal.filewatch.FileWatcherEvent;
import org.gradle.internal.filewatch.FileWatcherListener;
import org.gradle.internal.nativeintegration.filesystem.FileSystem;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.io.IOException;
import java.lang.ref.SoftReference;
import java.nio.file.ClosedWatchServiceException;
import java.nio.file.WatchService;
import java.util.List;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicReference;
public class WatchServiceFileWatcherBacking {
private static final Logger LOGGER = LoggerFactory.getLogger(WatchServiceFileWatcherBacking.class);
private final AtomicBoolean started = new AtomicBoolean();
private final AtomicBoolean running = new AtomicBoolean();
private final AtomicBoolean stopped = new AtomicBoolean();
private final AtomicReference<SoftReference<Thread>> pollerThreadReference = new AtomicReference<SoftReference<Thread>>();
private final Action<? super Throwable> onError;
private final WatchServiceRegistrar watchServiceRegistrar;
private final WatchService watchService;
private final WatchServicePoller poller;
private final FileWatcher fileWatcher = new FileWatcher() {
@Override
public boolean isRunning() {
return running.get();
}
@Override
public void watch(FileSystemSubset fileSystemSubset) throws IOException {
WatchServiceFileWatcherBacking.this.watchServiceRegistrar.watch(fileSystemSubset);
}
@Override
public void stop() {
WatchServiceFileWatcherBacking.this.stop();
}
};
WatchServiceFileWatcherBacking(Action<? super Throwable> onError, FileWatcherListener listener, WatchService watchService, FileSystem fileSystem) throws IOException {
this(onError, listener, watchService, new WatchServiceRegistrar(watchService, listener, fileSystem));
}
WatchServiceFileWatcherBacking(Action<? super Throwable> onError, FileWatcherListener listener, WatchService watchService, WatchServiceRegistrar watchServiceRegistrar) throws IOException {
this.onError = onError;
this.watchServiceRegistrar = watchServiceRegistrar;
this.watchService = watchService;
this.poller = new WatchServicePoller(watchService);
}
public FileWatcher start(ListeningExecutorService executorService) {
if (started.compareAndSet(false, true)) {
final ListenableFuture<?> runLoopFuture = executorService.submit(new Runnable() {
@Override
public void run() {
if (!stopped.get()) {
pollerThreadReference.set(new SoftReference<Thread>(Thread.currentThread()));
running.set(true);
try {
try {
pumpEvents();
} catch (InterruptedException e) {
// just stop
} catch (Throwable t) {
if (!(Throwables.getRootCause(t) instanceof InterruptedException)) {
stop();
onError.execute(t);
}
}
} finally {
stop();
}
}
}
});
// This is necessary so that the watcher indicates its not running if the runnable gets cancelled
Futures.addCallback(runLoopFuture, new FutureCallback<Object>() {
@Override
public void onSuccess(Object result) {
running.set(false);
}
@Override
public void onFailure(Throwable t) {
running.set(false);
}
});
return fileWatcher;
} else {
throw new IllegalStateException("file watcher is started");
}
}
private void pumpEvents() throws InterruptedException {
while (isRunning()) {
try {
List<FileWatcherEvent> events = poller.takeEvents();
if (events != null) {
deliverEvents(events);
}
} catch (ClosedWatchServiceException e) {
LOGGER.debug("Received ClosedWatchServiceException, stopping");
stop();
}
}
}
private void deliverEvents(List<FileWatcherEvent> events) {
for (FileWatcherEvent event : events) {
if (!isRunning()) {
LOGGER.debug("File watching isn't running, breaking out of event delivery.");
break;
}
if (LOGGER.isDebugEnabled()) {
LOGGER.debug("Received file system event: {}", event);
}
watchServiceRegistrar.onChange(fileWatcher, event);
}
}
private boolean isRunning() {
return running.get() && !Thread.currentThread().isInterrupted();
}
private void stop() {
if (stopped.compareAndSet(false, true)) {
if (running.compareAndSet(true, false)) {
LOGGER.debug("Stopping file watching");
interruptPollerThread();
try {
watchService.close();
} catch (IOException e) {
// ignore exception in shutdown
} catch (ClosedWatchServiceException e) {
// ignore
}
}
}
}
private void interruptPollerThread() {
SoftReference<Thread> threadSoftReference = pollerThreadReference.getAndSet(null);
if (threadSoftReference != null) {
Thread pollerThread = threadSoftReference.get();
if (pollerThread != null && pollerThread != Thread.currentThread()) {
// only interrupt poller thread if it's not current thread
LOGGER.debug("Interrupting poller thread '{}'", pollerThread.getName());
pollerThread.interrupt();
}
}
}
}