HADOOP-7144. Expose JMX metrics via JSON servlet.

Contributed by Robert Joseph Evans


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1131289 13f79535-47bb-0310-9956-ffa450edef68

CHANGES.txt

@@ -38,6 +38,9 @@ Trunk (unreleased changes)
     HADOOP-6832. Add an authentication plugin using a configurable static user
     for the web UI. (Owen O'Malley and Todd Lipcon via cdouglas)
 
+    HADOOP-7144. Expose JMX metrics via JSON servlet. (Robert Joseph Evans via
+    cdouglas)
+
   IMPROVEMENTS
 
     HADOOP-7042. Updates to test-patch.sh to include failed test names and

src/java/org/apache/hadoop/http/HttpServer.java

@@ -52,6 +52,7 @@
 import org.apache.hadoop.http.FilterContainer;
 import org.apache.hadoop.http.FilterInitializer;
 import org.apache.hadoop.http.HtmlQuoting;
+import org.apache.hadoop.jmx.JMXJsonServlet;
 import org.apache.hadoop.log.LogLevel;
 import org.apache.hadoop.metrics.MetricsServlet;
 import org.apache.hadoop.security.Krb5AndCertsSslSocketConnector;
@@ -287,6 +288,7 @@ protected void addDefaultServlets() {
     addServlet("stacks", "/stacks", StackServlet.class);
     addServlet("logLevel", "/logLevel", LogLevel.Servlet.class);
     addServlet("metrics", "/metrics", MetricsServlet.class);
+    addServlet("jmx", "/jmx", JMXJsonServlet.class);
     addServlet("conf", "/conf", ConfServlet.class);
   }
 

src/java/org/apache/hadoop/jmx/JMXJsonServlet.java

@@ -0,0 +1,327 @@
+/*
+ * 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.jmx;
+
+import java.io.IOException;
+import java.io.PrintWriter;
+import java.lang.management.ManagementFactory;
+import java.lang.reflect.Array;
+import java.util.Iterator;
+import java.util.Set;
+
+import javax.management.AttributeNotFoundException;
+import javax.management.InstanceNotFoundException;
+import javax.management.IntrospectionException;
+import javax.management.MBeanAttributeInfo;
+import javax.management.MBeanException;
+import javax.management.MBeanInfo;
+import javax.management.MBeanServer;
+import javax.management.MalformedObjectNameException;
+import javax.management.ObjectName;
+import javax.management.ReflectionException;
+import javax.management.openmbean.CompositeData;
+import javax.management.openmbean.CompositeType;
+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.http.HttpServer;
+import org.codehaus.jackson.JsonFactory;
+import org.codehaus.jackson.JsonGenerator;
+
+/*
+ * 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>
+ * For example <code>http://.../jmx?qry=Hadoop:*</code> will return
+ * all hadoop metrics exposed through JMX.
+ * <p>
+ * If the <code>qry</code> parameter is not formatted correctly then a
+ * 400 BAD REQUEST http response code will be returned. 
+ * <p>
+ * The return format is JSON and in the form
+ * <p>
+ *  <code><pre>
+ *  {
+ *    "beans" : [
+ *      {
+ *        "name":"bean-name"
+ *        ...
+ *      }
+ *    ]
+ *  }
+ *  </pre></code>
+ *  <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.
+ */
+public class JMXJsonServlet extends HttpServlet {
+  private static final Log LOG = LogFactory.getLog(JMXJsonServlet.class);
+
+  private static final long serialVersionUID = 1L;
+
+  // ----------------------------------------------------- Instance Variables
+  /**
+   * MBean server.
+   */
+  protected transient MBeanServer mBeanServer = null;
+
+  // --------------------------------------------------------- Public Methods
+  /**
+   * Initialize this servlet.
+   */
+  @Override
+  public void init() throws ServletException {
+    // Retrieve the MBean server
+    mBeanServer = ManagementFactory.getPlatformMBeanServer();
+  }
+
+  /**
+   * 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) {
+    try {
+      // Do the authorization
+      if (!HttpServer.hasAdministratorAccess(getServletContext(), request,
+          response)) {
+        return;
+      }
+
+      response.setContentType("application/json; charset=utf8");
+
+      PrintWriter writer = response.getWriter();
+
+      JsonFactory jsonFactory = new JsonFactory();
+      JsonGenerator jg = jsonFactory.createJsonGenerator(writer);
+      jg.useDefaultPrettyPrinter();
+      jg.writeStartObject();
+      if (mBeanServer == null) {
+        jg.writeStringField("result", "ERROR");
+        jg.writeStringField("message", "No MBeanServer could be found");
+        jg.close();
+        return;
+      }
+      String qry = request.getParameter("qry");
+      if (qry == null) {
+        qry = "*:*";
+      }
+      listBeans(jg, new ObjectName(qry));
+      jg.close();
+    } catch (IOException e) {
+      LOG.error("Caught an exception while processing JMX request", e);
+      response.setStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
+    } catch (MalformedObjectNameException e) {
+      LOG.error("Caught an exception while processing JMX request", e);
+      response.setStatus(HttpServletResponse.SC_BAD_REQUEST);
+    }
+  }
+
+  // --------------------------------------------------------- Private Methods
+  private void listBeans(JsonGenerator jg, ObjectName qry) throws IOException {
+    LOG.debug("Listing beans for "+qry);
+    Set<ObjectName> names = null;
+    names = mBeanServer.queryNames(qry, null);
+
+    jg.writeArrayFieldStart("beans");
+    Iterator<ObjectName> it = names.iterator();
+    while (it.hasNext()) {
+      ObjectName oname = it.next();
+      MBeanInfo minfo;
+      String code;
+      try {
+        minfo = mBeanServer.getMBeanInfo(oname);
+        code = minfo.getClassName();
+        try {
+          if ("org.apache.commons.modeler.BaseModelMBean".equals(code)) {
+            code = (String) mBeanServer.getAttribute(oname, "modelerType");
+          }
+        } catch (AttributeNotFoundException e) {
+          //Ignored the modelerType attribute was not found, so use the class name instead.
+        } catch (MBeanException e) {
+          //The code inside the attribute getter threw an exception so log it, and
+          // fall back on the class name
+          LOG.error("getting attribute modelerType of "+oname+" threw an exception", e);
+        } catch (RuntimeException e) {
+          //For some reason even with an MBeanException available to them Runtime exceptions
+          //can still find their way through, so treat them the same as MBeanException
+          LOG.error("getting attribute modelerType of "+oname+" threw an exception", e);
+        } catch (ReflectionException e) {
+          //This happens when the code inside the JMX bean (setter?? from the java docs)
+          //threw an exception, so log it and fall back on the class name
+          LOG.error("getting attribute modelerType of "+oname+" threw an exception", e);
+        }
+      } catch (InstanceNotFoundException e) {
+        //Ignored for some reason the bean was not found so don't output it
+        continue;
+      } catch (IntrospectionException e) {
+        //This is an internal error, something odd happened with reflection so log it and
+        //don't output the bean.
+        LOG.error("Problem while trying to process JMX query: "+qry+" with MBean "+oname, e); 
+        continue;
+      } catch (ReflectionException e) {
+        //This happens when the code inside the JMX bean threw an exception, so log it and
+        //don't output the bean.
+        LOG.error("Problem while trying to process JMX query: "+qry+" with MBean "+oname, e);
+        continue;
+      }
+
+      jg.writeStartObject();
+      jg.writeStringField("name", oname.toString());
+      // can't be null - I think
+
+      jg.writeStringField("modelerType", code);
+
+      MBeanAttributeInfo attrs[] = minfo.getAttributes();
+      for (int i = 0; i < attrs.length; i++) {
+        writeAttribute(jg, oname, attrs[i]);
+      }
+      //  LOG.error("Caught Error writing value ",t);
+      //  ExceptionUtils.handleThrowable(t);
+      //}
+      jg.writeEndObject();
+    }
+    jg.writeEndArray();
+  }
+  
+  private void writeAttribute(JsonGenerator jg, ObjectName oname, MBeanAttributeInfo attr) throws IOException {
+    if (!attr.isReadable()) {
+      return;
+    }
+    String attName = attr.getName();
+    if ("modelerType".equals(attName)) {
+      return;
+    }
+    if (attName.indexOf("=") >= 0 || attName.indexOf(":") >= 0
+        || attName.indexOf(" ") >= 0) {
+      return;
+    }
+    Object value = null;
+    try {
+      value = mBeanServer.getAttribute(oname, attName);
+    } catch (AttributeNotFoundException e) {
+      //Ignored the attribute was not found, which should never happen because the bean
+      //just told us that it has this attribute, but if this happens just don't output
+      //the attribute.
+      return;
+    } catch (MBeanException e) {
+      //The code inside the attribute getter threw an exception so log it, and
+      // skip outputting the attribute
+      LOG.error("getting attribute "+attName+" of "+oname+" threw an exception", e);
+      return;
+    } catch (RuntimeException e) {
+      //For some reason even with an MBeanException available to them Runtime exceptions
+      //can still find their way through, so treat them the same as MBeanException
+      LOG.error("getting attribute "+attName+" of "+oname+" threw an exception", e);
+      return;
+    } catch (ReflectionException e) {
+      //This happens when the code inside the JMX bean (setter?? from the java docs)
+      //threw an exception, so log it and skip outputting the attribute
+      LOG.error("getting attribute "+attName+" of "+oname+" threw an exception", e);
+      return;
+    } catch (InstanceNotFoundException e) {
+      //Ignored the mbean itself was not found, which should never happen because we
+      //just accessed it (perhaps something unregistered in-between) but if this
+      //happens just don't output the attribute.
+      return;
+    }
+
+    writeAttribute(jg, attName, value);
+  }
+  
+  private void writeAttribute(JsonGenerator jg, String attName, Object value) throws IOException {
+    jg.writeFieldName(attName);
+    writeObject(jg, value);
+  }
+  
+  private void writeObject(JsonGenerator jg, Object value) throws IOException {
+    if(value == null) {
+      jg.writeNull();
+    } else {
+      Class<?> c = value.getClass();
+      if (c.isArray()) {
+        jg.writeStartArray();
+        int len = Array.getLength(value);
+        for (int j = 0; j < len; j++) {
+          Object item = Array.get(value, j);
+          writeObject(jg, item);
+        }
+        jg.writeEndArray();
+      } else if(value instanceof Number) {
+        Number n = (Number)value;
+        jg.writeNumber(n.toString());
+      } else if(value instanceof Boolean) {
+        Boolean b = (Boolean)value;
+        jg.writeBoolean(b);
+      } else if(value instanceof CompositeData) {
+        CompositeData cds = (CompositeData)value;
+        CompositeType comp = cds.getCompositeType();
+        Set<String> keys = comp.keySet();
+        jg.writeStartObject();
+        for(String key: keys) {
+          writeAttribute(jg, key, cds.get(key));
+        }
+        jg.writeEndObject();
+      } else if(value instanceof TabularData) {
+        TabularData tds = (TabularData)value;
+        jg.writeStartArray();
+        for(Object entry : tds.values()) {
+          writeObject(jg, entry);
+        }
+        jg.writeEndArray();
+      } else {
+        jg.writeString(value.toString());
+      }
+    }
+  }
+}

src/java/org/apache/hadoop/jmx/package-info.java

@@ -0,0 +1,22 @@
+/*
+ * 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.
+ */
+
+/**
+ * This package provides access to JMX primarily through the
+ * {@link org.apache.hadoop.jmx.JMXJsonServlet} class.
+ */
+package org.apache.hadoop.jmx;

src/test/core/org/apache/hadoop/jmx/TestJMXJsonServlet.java

@@ -0,0 +1,69 @@
+/*
+ * 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.jmx;
+
+
+import java.net.URL;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+import org.apache.hadoop.http.HttpServer;
+import org.apache.hadoop.http.HttpServerFunctionalTest;
+import org.junit.AfterClass;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+public class TestJMXJsonServlet extends HttpServerFunctionalTest {
+  private   static final Log LOG = LogFactory.getLog(TestJMXJsonServlet.class);
+  private static HttpServer server;
+  private static URL baseUrl;
+
+  @BeforeClass public static void setup() throws Exception {
+    server = createTestServer();
+    server.start();
+    baseUrl = getServerURL(server);
+  }
+  
+  @AfterClass public static void cleanup() throws Exception {
+    server.stop();
+  }
+  
+  public static void assertReFind(String re, String value) {
+    Pattern p = Pattern.compile(re);
+    Matcher m = p.matcher(value);
+    assertTrue("'"+p+"' does not match "+value, m.find());
+  }
+  
+  @Test public void testQury() throws Exception {
+    String result = readOutput(new URL(baseUrl, "/jmx?qry=java.lang:type=Runtime"));
+    LOG.info("/jmx?qry=java.lang:type=Runtime RESULT: "+result);
+    assertReFind("\"name\"\\s*:\\s*\"java.lang:type=Runtime\"", result);
+    assertReFind("\"modelerType\"", result);
+    
+    result = readOutput(new URL(baseUrl, "/jmx?qry=java.lang:type=Memory"));
+    LOG.info("/jmx?qry=java.lang:type=Memory RESULT: "+result);
+    assertReFind("\"name\"\\s*:\\s*\"java.lang:type=Memory\"", result);
+    assertReFind("\"modelerType\"", result);
+    
+    result = readOutput(new URL(baseUrl, "/jmx"));
+    LOG.info("/jmx RESULT: "+result);
+    assertReFind("\"name\"\\s*:\\s*\"java.lang:type=Memory\"", result);
+  }
+}