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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.zookeeper.jmx;
import java.lang.management.ManagementFactory;
import java.util.Collection;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import javax.management.JMException;
import javax.management.MBeanServer;
import javax.management.MBeanServerFactory;
import javax.management.MalformedObjectNameException;
import javax.management.ObjectName;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* This class provides a unified interface for registering/unregistering of
* zookeeper MBeans with the platform MBean server. It builds a hierarchy of MBeans
* where each MBean represented by a filesystem-like path. Eventually, this hierarchy
* will be stored in the zookeeper data tree instance as a virtual data tree.
*/
public class MBeanRegistry {
public static final String DOMAIN = "org.apache.ZooKeeperService";
private static final Logger LOG = LoggerFactory.getLogger(MBeanRegistry.class);
private static volatile MBeanRegistry instance = new MBeanRegistry();
private final Object LOCK = new Object();
private Map<ZKMBeanInfo, String> mapBean2Path = new ConcurrentHashMap<ZKMBeanInfo, String>();
private MBeanServer mBeanServer;
/**
* Useful for unit tests. Change the MBeanRegistry instance
*
* @param instance new instance
*/
public static void setInstance(MBeanRegistry instance) {
MBeanRegistry.instance = instance;
}
public static MBeanRegistry getInstance() {
return instance;
}
public MBeanRegistry() {
try {
mBeanServer = ManagementFactory.getPlatformMBeanServer();
} catch (Error e) {
// Account for running within IKVM and create a new MBeanServer
// if the PlatformMBeanServer does not exist.
mBeanServer = MBeanServerFactory.createMBeanServer();
}
}
/**
* Return the underlying MBeanServer that is being
* used to register MBean's. The returned MBeanServer
* may be a new empty MBeanServer if running through IKVM.
*/
public MBeanServer getPlatformMBeanServer() {
return mBeanServer;
}
/**
* Registers a new MBean with the platform MBean server.
* @param bean the bean being registered
* @param parent if not null, the new bean will be registered as a child
* node of this parent.
*/
public void register(ZKMBeanInfo bean, ZKMBeanInfo parent) throws JMException {
assert bean != null;
String path = null;
if (parent != null) {
path = mapBean2Path.get(parent);
assert path != null;
}
path = makeFullPath(path, parent);
if (bean.isHidden()) {
return;
}
ObjectName oname = makeObjectName(path, bean);
try {
synchronized (LOCK) {
mBeanServer.registerMBean(bean, oname);
mapBean2Path.put(bean, path);
}
} catch (JMException e) {
LOG.warn("Failed to register MBean {}", bean.getName());
throw e;
}
}
/**
* Unregister the MBean identified by the path.
* @param path
* @param bean
*/
private void unregister(String path, ZKMBeanInfo bean) throws JMException {
if (path == null) {
return;
}
if (!bean.isHidden()) {
final ObjectName objName = makeObjectName(path, bean);
LOG.debug("Unregister MBean [{}]", objName);
synchronized (LOCK) {
mBeanServer.unregisterMBean(objName);
}
}
}
/**
* @return a {@link Collection} with the {@link ZKMBeanInfo} instances not
* unregistered. Mainly for testing purposes.
*/
public Set<ZKMBeanInfo> getRegisteredBeans() {
return new HashSet<ZKMBeanInfo>(mapBean2Path.keySet());
}
/**
* Unregister MBean.
* @param bean
*/
public void unregister(ZKMBeanInfo bean) {
if (bean == null) {
return;
}
String path = mapBean2Path.remove(bean);
try {
unregister(path, bean);
} catch (JMException e) {
LOG.warn("Error during unregister of [{}]", bean.getName(), e);
} catch (Throwable t) {
LOG.error("Unexpected exception during unregister of [{}]. It should be reviewed and fixed.", bean.getName(), t);
}
}
/**
* Generate a filesystem-like path.
* @param prefix path prefix
* @param name path elements
* @return absolute path
*/
public String makeFullPath(String prefix, String... name) {
StringBuilder sb = new StringBuilder(prefix == null ? "/" : (prefix.equals("/") ? prefix : prefix + "/"));
boolean first = true;
for (String s : name) {
if (s == null) {
continue;
}
if (!first) {
sb.append("/");
} else {
first = false;
}
sb.append(s);
}
return sb.toString();
}
protected String makeFullPath(String prefix, ZKMBeanInfo bean) {
return makeFullPath(prefix, bean == null ? null : bean.getName());
}
/**
* This takes a path, such as /a/b/c, and converts it to
* name0=a,name1=b,name2=c
*/
private int tokenize(StringBuilder sb, String path, int index) {
String[] tokens = path.split("/");
for (String s : tokens) {
if (s.length() == 0) {
continue;
}
sb.append("name").append(index++).append("=").append(s).append(",");
}
return index;
}
/**
* Builds an MBean path and creates an ObjectName instance using the path.
* @param path MBean path
* @param bean the MBean instance
* @return ObjectName to be registered with the platform MBean server
*/
protected ObjectName makeObjectName(String path, ZKMBeanInfo bean) throws MalformedObjectNameException {
if (path == null) {
return null;
}
StringBuilder beanName = new StringBuilder(DOMAIN + ":");
int counter = 0;
counter = tokenize(beanName, path, counter);
tokenize(beanName, bean.getName(), counter);
beanName.deleteCharAt(beanName.length() - 1);
try {
return new ObjectName(beanName.toString());
} catch (MalformedObjectNameException e) {
LOG.warn("Invalid name \"{}\" for class {}", beanName, bean.getClass());
throw e;
}
}
}
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