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/**
* 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.hadoop.hbase.util;
import java.io.File;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.HashMap;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.hbase.classification.InterfaceAudience;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileStatus;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
/**
* This is a class loader that can load classes dynamically from new
* jar files under a configured folder. The paths to the jar files are
* converted to URLs, and URLClassLoader logic is actually used to load
* classes. This class loader always uses its parent class loader
* to load a class at first. Only if its parent class loader
* can not load a class, we will try to load it using the logic here.
*
* The configured folder can be a HDFS path. In this case, the jar files
* under that folder will be copied to local at first under ${hbase.local.dir}/jars/.
* The local copy will be updated if the remote copy is updated, according to its
* last modified timestamp.
*
* We can't unload a class already loaded. So we will use the existing
* jar files we already know to load any class which can't be loaded
* using the parent class loader. If we still can't load the class from
* the existing jar files, we will check if any new jar file is added,
* if so, we will load the new jar file and try to load the class again.
* If still failed, a class not found exception will be thrown.
*
* Be careful in uploading new jar files and make sure all classes
* are consistent, otherwise, we may not be able to load your
* classes properly.
*/
@InterfaceAudience.Private
public class DynamicClassLoader extends ClassLoaderBase {
private static final Log LOG =
LogFactory.getLog(DynamicClassLoader.class);
// Dynamic jars are put under ${hbase.local.dir}/jars/
private static final String DYNAMIC_JARS_DIR = File.separator
+ "jars" + File.separator;
private static final String DYNAMIC_JARS_DIR_KEY = "hbase.dynamic.jars.dir";
private static final String DYNAMIC_JARS_OPTIONAL_CONF_KEY = "hbase.use.dynamic.jars";
private static final boolean DYNAMIC_JARS_OPTIONAL_DEFAULT = true;
private boolean useDynamicJars;
private File localDir;
// FileSystem of the remote path, set only if remoteDir != null
private FileSystem remoteDirFs;
private Path remoteDir;
// Last modified time of local jars
private HashMap jarModifiedTime;
/**
* Creates a DynamicClassLoader that can load classes dynamically
* from jar files under a specific folder.
*
* @param conf the configuration for the cluster.
* @param parent the parent ClassLoader to set.
*/
public DynamicClassLoader(
final Configuration conf, final ClassLoader parent) {
super(parent);
useDynamicJars = conf.getBoolean(
DYNAMIC_JARS_OPTIONAL_CONF_KEY, DYNAMIC_JARS_OPTIONAL_DEFAULT);
if (useDynamicJars) {
initTempDir(conf);
}
}
// FindBugs: Making synchronized to avoid IS2_INCONSISTENT_SYNC complaints about
// remoteDirFs and jarModifiedTime being part synchronized protected.
private synchronized void initTempDir(final Configuration conf) {
jarModifiedTime = new HashMap();
String localDirPath = conf.get(
LOCAL_DIR_KEY, DEFAULT_LOCAL_DIR) + DYNAMIC_JARS_DIR;
localDir = new File(localDirPath);
if (!localDir.mkdirs() && !localDir.isDirectory()) {
throw new RuntimeException("Failed to create local dir " + localDir.getPath()
+ ", DynamicClassLoader failed to init");
}
String remotePath = conf.get(DYNAMIC_JARS_DIR_KEY);
if (remotePath == null || remotePath.equals(localDirPath)) {
remoteDir = null; // ignore if it is the same as the local path
} else {
remoteDir = new Path(remotePath);
try {
remoteDirFs = remoteDir.getFileSystem(conf);
} catch (IOException ioe) {
LOG.warn("Failed to identify the fs of dir "
+ remoteDir + ", ignored", ioe);
remoteDir = null;
}
}
}
@Override
public Class loadClass(String name)
throws ClassNotFoundException {
try {
return parent.loadClass(name);
} catch (ClassNotFoundException e) {
if (LOG.isDebugEnabled()) {
LOG.debug("Class " + name + " not found - using dynamical class loader");
}
if (useDynamicJars) {
return tryRefreshClass(name);
}
throw e;
}
}
private Class tryRefreshClass(String name)
throws ClassNotFoundException {
synchronized (getClassLoadingLock(name)) {
// Check whether the class has already been loaded:
Class clasz = findLoadedClass(name);
if (clasz != null) {
if (LOG.isDebugEnabled()) {
LOG.debug("Class " + name + " already loaded");
}
}
else {
try {
if (LOG.isDebugEnabled()) {
LOG.debug("Finding class: " + name);
}
clasz = findClass(name);
} catch (ClassNotFoundException cnfe) {
// Load new jar files if any
if (LOG.isDebugEnabled()) {
LOG.debug("Loading new jar files, if any");
}
loadNewJars();
if (LOG.isDebugEnabled()) {
LOG.debug("Finding class again: " + name);
}
clasz = findClass(name);
}
}
return clasz;
}
}
private synchronized void loadNewJars() {
// Refresh local jar file lists
File[] files = localDir == null ? null : localDir.listFiles();
if (files != null) {
for (File file : files) {
String fileName = file.getName();
if (jarModifiedTime.containsKey(fileName)) {
continue;
}
if (file.isFile() && fileName.endsWith(".jar")) {
jarModifiedTime.put(fileName, Long.valueOf(file.lastModified()));
try {
URL url = file.toURI().toURL();
addURL(url);
} catch (MalformedURLException mue) {
// This should not happen, just log it
LOG.warn("Failed to load new jar " + fileName, mue);
}
}
}
}
// Check remote files
FileStatus[] statuses = null;
if (remoteDir != null) {
try {
statuses = remoteDirFs.listStatus(remoteDir);
} catch (IOException ioe) {
LOG.warn("Failed to check remote dir status " + remoteDir, ioe);
}
}
if (statuses == null || statuses.length == 0) {
return; // no remote files at all
}
for (FileStatus status: statuses) {
if (status.isDirectory()) continue; // No recursive lookup
Path path = status.getPath();
String fileName = path.getName();
if (!fileName.endsWith(".jar")) {
if (LOG.isDebugEnabled()) {
LOG.debug("Ignored non-jar file " + fileName);
}
continue; // Ignore non-jar files
}
Long cachedLastModificationTime = jarModifiedTime.get(fileName);
if (cachedLastModificationTime != null) {
long lastModified = status.getModificationTime();
if (lastModified < cachedLastModificationTime.longValue()) {
// There could be some race, for example, someone uploads
// a new one right in the middle the old one is copied to
// local. We can check the size as well. But it is still
// not guaranteed. This should be rare. Most likely,
// we already have the latest one.
// If you are unlucky to hit this race issue, you have
// to touch the remote jar to update its last modified time
continue;
}
}
try {
// Copy it to local
File dst = new File(localDir, fileName);
remoteDirFs.copyToLocalFile(path, new Path(dst.getPath()));
jarModifiedTime.put(fileName, Long.valueOf(dst.lastModified()));
URL url = dst.toURI().toURL();
addURL(url);
} catch (IOException ioe) {
LOG.warn("Failed to load new jar " + fileName, ioe);
}
}
}
}