/*
* 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.start.classloader.vfs;
import static java.util.concurrent.TimeUnit.SECONDS;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.RejectedExecutionException;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.ThreadPoolExecutor;
import org.apache.commons.vfs2.FileChangeEvent;
import org.apache.commons.vfs2.FileListener;
import org.apache.commons.vfs2.FileObject;
import org.apache.commons.vfs2.FileSystemException;
import org.apache.commons.vfs2.FileSystemManager;
import org.apache.commons.vfs2.impl.DefaultFileMonitor;
import org.apache.commons.vfs2.impl.VFSClassLoader;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* Classloader that delegates operations to a VFSClassLoader object. This class also listens for changes in any of the files/directories that are in the
* classpath and will recreate the delegate object if there is any change in the classpath.
*
*/
public class AccumuloReloadingVFSClassLoader implements FileListener, ReloadingClassLoader {
private static final Logger log = LoggerFactory.getLogger(AccumuloReloadingVFSClassLoader.class);
// set to 5 mins. The rational behind this large time is to avoid a gazillion tservers all asking the name node for info too frequently.
private static final int DEFAULT_TIMEOUT = 5 * 60 * 1000;
private FileObject[] files;
private VFSClassLoader cl;
private final ReloadingClassLoader parent;
private final String uris;
private final DefaultFileMonitor monitor;
private final boolean preDelegate;
private final ThreadPoolExecutor executor;
{
BlockingQueue<Runnable> queue = new ArrayBlockingQueue<>(2);
ThreadFactory factory = new ThreadFactory() {
@Override
public Thread newThread(Runnable r) {
Thread t = new Thread(r);
t.setDaemon(true);
return t;
}
};
executor = new ThreadPoolExecutor(1, 1, 1, SECONDS, queue, factory);
}
private final Runnable refresher = new Runnable() {
@Override
public void run() {
while (!executor.isTerminating()) {
try {
FileSystemManager vfs = AccumuloVFSClassLoader.generateVfs();
FileObject[] files = AccumuloVFSClassLoader.resolve(vfs, uris);
log.debug("Rebuilding dynamic classloader using files- " + stringify(files));
VFSClassLoader cl;
if (preDelegate)
cl = new VFSClassLoader(files, vfs, parent.getClassLoader());
else
cl = new PostDelegatingVFSClassLoader(files, vfs, parent.getClassLoader());
updateClassloader(files, cl);
return;
} catch (Exception e) {
log.error("{}", e.getMessage(), e);
try {
Thread.sleep(DEFAULT_TIMEOUT);
} catch (InterruptedException ie) {
log.error("{}", e.getMessage(), ie);
}
}
}
}
};
public String stringify(FileObject[] files) {
StringBuilder sb = new StringBuilder();
sb.append('[');
String delim = "";
for (FileObject file : files) {
sb.append(delim);
delim = ", ";
sb.append(file.getName());
}
sb.append(']');
return sb.toString();
}
@Override
public synchronized ClassLoader getClassLoader() {
if (cl.getParent() != parent.getClassLoader()) {
scheduleRefresh();
}
return cl;
}
private void scheduleRefresh() {
try {
executor.execute(refresher);
} catch (RejectedExecutionException e) {
log.trace("Ignoring refresh request (already refreshing)");
}
}
private synchronized void updateClassloader(FileObject[] files, VFSClassLoader cl) {
this.files = files;
this.cl = cl;
}
public AccumuloReloadingVFSClassLoader(String uris, FileSystemManager vfs, ReloadingClassLoader parent, long monitorDelay, boolean preDelegate)
throws FileSystemException {
this.uris = uris;
this.parent = parent;
this.preDelegate = preDelegate;
ArrayList<FileObject> pathsToMonitor = new ArrayList<>();
files = AccumuloVFSClassLoader.resolve(vfs, uris, pathsToMonitor);
if (preDelegate)
cl = new VFSClassLoader(files, vfs, parent.getClassLoader());
else
cl = new PostDelegatingVFSClassLoader(files, vfs, parent.getClassLoader());
monitor = new DefaultFileMonitor(this);
monitor.setDelay(monitorDelay);
monitor.setRecursive(false);
for (FileObject file : pathsToMonitor) {
monitor.addFile(file);
log.debug("monitoring " + file);
}
monitor.start();
}
public AccumuloReloadingVFSClassLoader(String uris, FileSystemManager vfs, final ReloadingClassLoader parent, boolean preDelegate) throws FileSystemException {
this(uris, vfs, parent, DEFAULT_TIMEOUT, preDelegate);
}
synchronized public FileObject[] getFiles() {
return Arrays.copyOf(this.files, this.files.length);
}
/**
* Should be ok if this is not called because the thread started by DefaultFileMonitor is a daemon thread
*/
public void close() {
executor.shutdownNow();
monitor.stop();
}
@Override
public void fileCreated(FileChangeEvent event) throws Exception {
if (log.isDebugEnabled())
log.debug(event.getFile().getURL().toString() + " created, recreating classloader");
scheduleRefresh();
}
@Override
public void fileDeleted(FileChangeEvent event) throws Exception {
if (log.isDebugEnabled())
log.debug(event.getFile().getURL().toString() + " deleted, recreating classloader");
scheduleRefresh();
}
@Override
public void fileChanged(FileChangeEvent event) throws Exception {
if (log.isDebugEnabled())
log.debug(event.getFile().getURL().toString() + " changed, recreating classloader");
scheduleRefresh();
}
@Override
public String toString() {
StringBuilder buf = new StringBuilder();
for (FileObject f : files) {
try {
buf.append("\t").append(f.getURL().toString()).append("\n");
} catch (FileSystemException e) {
log.error("Error getting URL for file", e);
}
}
return buf.toString();
}
}