1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17
18 package org.apache.hadoop.hbase.http.jmx;
19
20 import java.io.IOException;
21 import java.io.PrintWriter;
22 import java.lang.management.ManagementFactory;
23
24 import javax.management.MBeanServer;
25 import javax.management.MalformedObjectNameException;
26 import javax.management.ObjectName;
27 import javax.management.ReflectionException;
28 import javax.management.RuntimeErrorException;
29 import javax.management.RuntimeMBeanException;
30 import javax.management.openmbean.CompositeData;
31 import javax.management.openmbean.TabularData;
32 import javax.servlet.ServletException;
33 import javax.servlet.http.HttpServlet;
34 import javax.servlet.http.HttpServletRequest;
35 import javax.servlet.http.HttpServletResponse;
36
37 import org.apache.commons.logging.Log;
38 import org.apache.commons.logging.LogFactory;
39 import org.apache.hadoop.hbase.http.HttpServer;
40 import org.apache.hadoop.hbase.util.JSONBean;
41
42 /*
43 * This servlet is based off of the JMXProxyServlet from Tomcat 7.0.14. It has
44 * been rewritten to be read only and to output in a JSON format so it is not
45 * really that close to the original.
46 */
47 /**
48 * Provides Read only web access to JMX.
49 * <p>
50 * This servlet generally will be placed under the /jmx URL for each
51 * HttpServer. It provides read only
52 * access to JMX metrics. The optional <code>qry</code> parameter
53 * may be used to query only a subset of the JMX Beans. This query
54 * functionality is provided through the
55 * {@link MBeanServer#queryNames(ObjectName, javax.management.QueryExp)}
56 * method.
57 * <p>
58 * For example <code>http://.../jmx?qry=Hadoop:*</code> will return
59 * all hadoop metrics exposed through JMX.
60 * <p>
61 * The optional <code>get</code> parameter is used to query an specific
62 * attribute of a JMX bean. The format of the URL is
63 * <code>http://.../jmx?get=MXBeanName::AttributeName<code>
64 * <p>
65 * For example
66 * <code>
67 * http://../jmx?get=Hadoop:service=NameNode,name=NameNodeInfo::ClusterId
68 * </code> will return the cluster id of the namenode mxbean.
69 * <p>
70 * If the <code>qry</code> or the <code>get</code> parameter is not formatted
71 * correctly then a 400 BAD REQUEST http response code will be returned.
72 * <p>
73 * If a resouce such as a mbean or attribute can not be found,
74 * a 404 SC_NOT_FOUND http response code will be returned.
75 * <p>
76 * The return format is JSON and in the form
77 * <p>
78 * <code><pre>
79 * {
80 * "beans" : [
81 * {
82 * "name":"bean-name"
83 * ...
84 * }
85 * ]
86 * }
87 * </pre></code>
88 * <p>
89 * The servlet attempts to convert the the JMXBeans into JSON. Each
90 * bean's attributes will be converted to a JSON object member.
91 *
92 * If the attribute is a boolean, a number, a string, or an array
93 * it will be converted to the JSON equivalent.
94 *
95 * If the value is a {@link CompositeData} then it will be converted
96 * to a JSON object with the keys as the name of the JSON member and
97 * the value is converted following these same rules.
98 *
99 * If the value is a {@link TabularData} then it will be converted
100 * to an array of the {@link CompositeData} elements that it contains.
101 *
102 * All other objects will be converted to a string and output as such.
103 *
104 * The bean's name and modelerType will be returned for all beans.
105 *
106 * Optional paramater "callback" should be used to deliver JSONP response.
107 *
108 */
109 public class JMXJsonServlet extends HttpServlet {
110 private static final Log LOG = LogFactory.getLog(JMXJsonServlet.class);
111
112 private static final long serialVersionUID = 1L;
113
114 private static final String CALLBACK_PARAM = "callback";
115 /**
116 * If query string includes 'description', then we will emit bean and attribute descriptions to
117 * output IFF they are not null and IFF the description is not the same as the attribute name:
118 * i.e. specify an URL like so: /jmx?description=true
119 */
120 private static final String INCLUDE_DESCRIPTION = "description";
121
122 /**
123 * MBean server.
124 */
125 protected transient MBeanServer mBeanServer;
126
127 protected transient JSONBean jsonBeanWriter;
128
129 /**
130 * Initialize this servlet.
131 */
132 @Override
133 public void init() throws ServletException {
134 // Retrieve the MBean server
135 mBeanServer = ManagementFactory.getPlatformMBeanServer();
136 this.jsonBeanWriter = new JSONBean();
137 }
138
139 /**
140 * Process a GET request for the specified resource.
141 *
142 * @param request
143 * The servlet request we are processing
144 * @param response
145 * The servlet response we are creating
146 */
147 @Override
148 public void doGet(HttpServletRequest request, HttpServletResponse response) {
149 try {
150 if (!HttpServer.isInstrumentationAccessAllowed(getServletContext(), request, response)) {
151 return;
152 }
153 String jsonpcb = null;
154 PrintWriter writer = null;
155 JSONBean.Writer beanWriter = null;
156 try {
157 writer = response.getWriter();
158 beanWriter = this.jsonBeanWriter.open(writer);
159 // "callback" parameter implies JSONP outpout
160 jsonpcb = request.getParameter(CALLBACK_PARAM);
161 if (jsonpcb != null) {
162 response.setContentType("application/javascript; charset=utf8");
163 writer.write(jsonpcb + "(");
164 } else {
165 response.setContentType("application/json; charset=utf8");
166 }
167 // Should we output description on each attribute and bean?
168 String tmpStr = request.getParameter(INCLUDE_DESCRIPTION);
169 boolean description = tmpStr != null && tmpStr.length() > 0;
170
171 // query per mbean attribute
172 String getmethod = request.getParameter("get");
173 if (getmethod != null) {
174 String[] splitStrings = getmethod.split("\\:\\:");
175 if (splitStrings.length != 2) {
176 beanWriter.write("result", "ERROR");
177 beanWriter.write("message", "query format is not as expected.");
178 beanWriter.flush();
179 response.setStatus(HttpServletResponse.SC_BAD_REQUEST);
180 return;
181 }
182 if (beanWriter.write(this.mBeanServer, new ObjectName(splitStrings[0]),
183 splitStrings[1], description) != 0) {
184 beanWriter.flush();
185 response.setStatus(HttpServletResponse.SC_BAD_REQUEST);
186 }
187 return;
188 }
189
190 // query per mbean
191 String qry = request.getParameter("qry");
192 if (qry == null) {
193 qry = "*:*";
194 }
195 if (beanWriter.write(this.mBeanServer, new ObjectName(qry), null, description) != 0) {
196 beanWriter.flush();
197 response.setStatus(HttpServletResponse.SC_BAD_REQUEST);
198 }
199 } finally {
200 if (beanWriter != null) beanWriter.close();
201 if (jsonpcb != null) {
202 writer.write(");");
203 }
204 if (writer != null) {
205 writer.close();
206 }
207 }
208 } catch (IOException e) {
209 LOG.error("Caught an exception while processing JMX request", e);
210 response.setStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
211 } catch (MalformedObjectNameException e) {
212 LOG.error("Caught an exception while processing JMX request", e);
213 response.setStatus(HttpServletResponse.SC_BAD_REQUEST);
214 }
215 }
216 }