/*
* 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.http.jmx;
import java.io.IOException;
import java.io.PrintWriter;
import java.lang.management.ManagementFactory;
import javax.management.MBeanServer;
import javax.management.MalformedObjectNameException;
import javax.management.ObjectName;
import javax.management.openmbean.CompositeData;
import javax.management.openmbean.TabularData;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.hbase.http.HttpServer;
import org.apache.hadoop.hbase.util.JSONBean;
/*
* This servlet is based off of the JMXProxyServlet from Tomcat 7.0.14. It has
* been rewritten to be read only and to output in a JSON format so it is not
* really that close to the original.
*/
/**
* Provides Read only web access to JMX.
* <p>
* This servlet generally will be placed under the /jmx URL for each
* HttpServer. It provides read only
* access to JMX metrics. The optional <code>qry</code> parameter
* may be used to query only a subset of the JMX Beans. This query
* functionality is provided through the
* {@link MBeanServer#queryNames(ObjectName, javax.management.QueryExp)}
* method.
* </p>
* <p>
* For example <code>http://.../jmx?qry=Hadoop:*</code> will return
* all hadoop metrics exposed through JMX.
* </p>
* <p>
* The optional <code>get</code> parameter is used to query an specific
* attribute of a JMX bean. The format of the URL is
* <code>http://.../jmx?get=MXBeanName::AttributeName</code>
* </p>
* <p>
* For example
* <code>
* http://../jmx?get=Hadoop:service=NameNode,name=NameNodeInfo::ClusterId
* </code> will return the cluster id of the namenode mxbean.
* </p>
* <p>
* If the <code>qry</code> or the <code>get</code> parameter is not formatted
* correctly then a 400 BAD REQUEST http response code will be returned.
* </p>
* <p>
* If a resouce such as a mbean or attribute can not be found,
* a 404 SC_NOT_FOUND http response code will be returned.
* </p>
* <p>
* The return format is JSON and in the form
* </p>
* <pre><code>
* {
* "beans" : [
* {
* "name":"bean-name"
* ...
* }
* ]
* }
* </code></pre>
* <p>
* The servlet attempts to convert the the JMXBeans into JSON. Each
* bean's attributes will be converted to a JSON object member.
*
* If the attribute is a boolean, a number, a string, or an array
* it will be converted to the JSON equivalent.
*
* If the value is a {@link CompositeData} then it will be converted
* to a JSON object with the keys as the name of the JSON member and
* the value is converted following these same rules.
*
* If the value is a {@link TabularData} then it will be converted
* to an array of the {@link CompositeData} elements that it contains.
*
* All other objects will be converted to a string and output as such.
*
* The bean's name and modelerType will be returned for all beans.
*
* Optional paramater "callback" should be used to deliver JSONP response.
* </p>
*
*/
public class JMXJsonServlet extends HttpServlet {
private static final Log LOG = LogFactory.getLog(JMXJsonServlet.class);
private static final long serialVersionUID = 1L;
private static final String CALLBACK_PARAM = "callback";
/**
* If query string includes 'description', then we will emit bean and attribute descriptions to
* output IFF they are not null and IFF the description is not the same as the attribute name:
* i.e. specify an URL like so: /jmx?description=true
*/
private static final String INCLUDE_DESCRIPTION = "description";
/**
* MBean server.
*/
protected transient MBeanServer mBeanServer;
protected transient JSONBean jsonBeanWriter;
/**
* Initialize this servlet.
*/
@Override
public void init() throws ServletException {
// Retrieve the MBean server
mBeanServer = ManagementFactory.getPlatformMBeanServer();
this.jsonBeanWriter = new JSONBean();
}
/**
* Process a GET request for the specified resource.
*
* @param request
* The servlet request we are processing
* @param response
* The servlet response we are creating
*/
@Override
public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException {
try {
if (!HttpServer.isInstrumentationAccessAllowed(getServletContext(), request, response)) {
return;
}
String jsonpcb = null;
PrintWriter writer = null;
JSONBean.Writer beanWriter = null;
try {
jsonpcb = checkCallbackName(request.getParameter(CALLBACK_PARAM));
writer = response.getWriter();
beanWriter = this.jsonBeanWriter.open(writer);
// "callback" parameter implies JSONP outpout
if (jsonpcb != null) {
response.setContentType("application/javascript; charset=utf8");
writer.write(jsonpcb + "(");
} else {
response.setContentType("application/json; charset=utf8");
}
// Should we output description on each attribute and bean?
String tmpStr = request.getParameter(INCLUDE_DESCRIPTION);
boolean description = tmpStr != null && tmpStr.length() > 0;
// query per mbean attribute
String getmethod = request.getParameter("get");
if (getmethod != null) {
String[] splitStrings = getmethod.split("\\:\\:");
if (splitStrings.length != 2) {
beanWriter.write("result", "ERROR");
beanWriter.write("message", "query format is not as expected.");
beanWriter.flush();
response.setStatus(HttpServletResponse.SC_BAD_REQUEST);
return;
}
if (beanWriter.write(this.mBeanServer, new ObjectName(splitStrings[0]),
splitStrings[1], description) != 0) {
beanWriter.flush();
response.setStatus(HttpServletResponse.SC_BAD_REQUEST);
}
return;
}
// query per mbean
String qry = request.getParameter("qry");
if (qry == null) {
qry = "*:*";
}
if (beanWriter.write(this.mBeanServer, new ObjectName(qry), null, description) != 0) {
beanWriter.flush();
response.setStatus(HttpServletResponse.SC_BAD_REQUEST);
}
} finally {
if (beanWriter != null) beanWriter.close();
if (jsonpcb != null) {
writer.write(");");
}
if (writer != null) {
writer.close();
}
}
} catch (IOException e) {
LOG.error("Caught an exception while processing JMX request", e);
response.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
} catch (MalformedObjectNameException e) {
LOG.error("Caught an exception while processing JMX request", e);
response.sendError(HttpServletResponse.SC_BAD_REQUEST);
}
}
/**
* Verifies that the callback property, if provided, is purely alphanumeric.
* This prevents a malicious callback name (that is javascript code) from being
* returned by the UI to an unsuspecting user.
*
* @param callbackName The callback name, can be null.
* @return The callback name
* @throws IOException If the name is disallowed.
*/
private String checkCallbackName(String callbackName) throws IOException {
if (null == callbackName) {
return null;
}
if (callbackName.matches("[A-Za-z0-9_]+")) {
return callbackName;
}
throw new IOException("'callback' must be alphanumeric");
}
}