Package org.apache.hadoop.hbase.http.jmx

Class JMXJsonServlet

java.lang.Object
javax.servlet.GenericServlet
javax.servlet.http.HttpServlet
org.apache.hadoop.hbase.http.jmx.JMXJsonServlet
All Implemented Interfaces:
Serializable, javax.servlet.Servlet, javax.servlet.ServletConfig
@Private public class JMXJsonServlet extends javax.servlet.http.HttpServlet
Provides Read only web access to JMX.

This servlet generally will be placed under the /jmx URL for each HttpServer. It provides read only access to JMX metrics. The optional qry parameter may be used to query only a subset of the JMX Beans. This query functionality is provided through the MBeanServer.queryNames(ObjectName, javax.management.QueryExp) method.

For example http://.../jmx?qry=Hadoop:* will return all hadoop metrics exposed through JMX.

The optional get parameter is used to query an specific attribute of a JMX bean. The format of the URL is http://.../jmx?get=MXBeanName::AttributeName

For example http://../jmx?get=Hadoop:service=NameNode,name=NameNodeInfo::ClusterId will return the cluster id of the namenode mxbean.

If we are not sure on the exact attribute and we want to get all the attributes that match one or more given pattern then the format is http://.../jmx?get=MXBeanName::*[RegExp1],*[RegExp2]

For example

http://../jmx?get=Hadoop:service=HBase,name=RegionServer,sub=Tables::[a-zA-z_0-9]*memStoreSize

http://../jmx?get=Hadoop:service=HBase,name=RegionServer,sub=Tables::[a-zA-z_0-9]*memStoreSize,[a-zA-z_0-9]*storeFileSize

If the qry or the get parameter is not formatted correctly then a 400 BAD REQUEST http response code will be returned.

If a resouce such as a mbean or attribute can not be found, a 404 SC_NOT_FOUND http response code will be returned.

The return format is JSON and in the form 

 
  {
    "beans" : [
      {
        "name":"bean-name"
        ...
      }
    ]
  }

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 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 TabularData then it will be converted to an array of the 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.

See Also:

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    private static final String
    CALLBACK_PARAM
     
    private static final String
    INCLUDE_DESCRIPTION
    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.
    protected JSONBean
    jsonBeanWriter
     
    private static final org.slf4j.Logger
    LOG
     
    protected MBeanServer
    mBeanServer
    MBean server.
    private static final long
    serialVersionUID
     

  • Constructor Summary

    Constructors
    Constructor
    Description
    JMXJsonServlet()
     

  • Method Summary

    Modifier and Type
    Method
    Description
    private String
    checkCallbackName(String callbackName)
    Verifies that the callback property, if provided, is purely alphanumeric.
    void
    doGet(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response)
    Process a GET request for the specified resource.
    void
    init()
    Initialize this servlet.

    Methods inherited from class javax.servlet.http.HttpServlet

    doDelete, doHead, doOptions, doPost, doPut, doTrace, getLastModified, service, service

    Methods inherited from class javax.servlet.GenericServlet

    destroy, getInitParameter, getInitParameterNames, getServletConfig, getServletContext, getServletInfo, getServletName, init, log, log

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Field Details

  • Constructor Details

  • Method Details

    • init

      public void init() throws javax.servlet.ServletException
      Initialize this servlet.
      Overrides:
      init in class javax.servlet.GenericServlet
      Throws:
      javax.servlet.ServletException

    • doGet

      public void doGet(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response) throws IOException
      Process a GET request for the specified resource. The servlet request we are processing The servlet response we are creating
      Overrides:
      doGet in class javax.servlet.http.HttpServlet
      Throws:
      IOException

    • checkCallbackName

      private String checkCallbackName(String callbackName) throws IOException
      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.
      Parameters:
      callbackName - The callback name, can be null.
      Returns:
      The callback name
      Throws:
      IOException - If the name is disallowed.