How to reliably count active sessions in J2EE web application

And some listener examples as well
http://www.java2s.com/Code/Java/Servlets/Listener.htm

Regards,
   Tomas Helgi

I agree with Tomas.  Also look at this old discussion.  
http://www.experts-exchange.com/Programming/Languages/Java/J2EE/JSP/Q_20514811.html

Thanks for the links to the various examples of custom classes for counting sessions.  However, I am still unsure about a couple of things:

1.  Assuming I use one of the sample classes, how do I get the session count values into a batch script so I can output to a simple log file?  Can I do something like this in a batch script:

A HttpSessionListener could do steps 1,2,3, and 4.  Maybe something like  this.

public class UsersListener implements HttpSessionListener {
  private Hashtable sessionsTable = null;
  private ArrayList aliveTimeList = new ArrayList();
  Timer timer = new Timer();
  timer.scheduleAtFixedRate(timerTask,firstTime,period);
                                                   
  private int getCount(){
                         sessionsTable.size();
  }
  private synchronized ArrayList getCurrentList(){
                                                  // TO DO: get list and make a new one
  }
  public void sessionCreated(HttpSessionEvent event) {
                           String id = event.getSession().getId();
                           if(sessionsTable == null)sessionsTable = new Hashtable();
                           sessionsTable.put(id, System.currentTimeMillis());
                           
  }
  public void sessionDestroyed(HttpSessionEvent event) {
                           String id = event.getSession().getId();
                           if(sessionsTable.containsKey(id)){
                                 long aliveTime = System.currentTimeMillis() - sessionsTable.get(id);
                                 aliveTimeList.add(new Long(aliveTime));
                                 sessionsTable.remove(id);          
                           }
                           
  }
}
// TO DO: TimerTask that will get Count and list and write to log file.
//        think about synchronization more
//  I will have more time to work on this weekend.

Can I avoid writing a custom class completely by using twiddle? I know next to nothing about twiddle, and the little I do know I have learned in the past hour by Googling it. From what I can see it will allow me to execute a command which will return any one of the values which is available via the JBoss Management Console.

Is this easier then writing a class?

>Can I avoid writing a custom class completely by using twiddle?    
I don't know anything about twiddle. I don't use jboss either.   I use Tomcat.

That might be an issue - I am using JBoss 4.0.5

Hi Tomas,

One person suggested I have a look at the "JBoss Management Console" (http://my-server:8180/web-console/),

     "...then in the console function tree find: Monitoring - > Web Status -> Full Status.
     You will get a page with loads of stats on the right side.
     Find [Application list] and link to your application, simply click on it
     and at the top of the page you will see all the stats that you need..."

I had a look at this and it looks perfect - it gives me more information than I was expecting, like Active sessions, Session count, Max active sessions, Rejected session creations, Expired sessions, Longest session alive time, and Average session alive time.  I am really only interested in Active Sessions.

Do you know of a way to retrieve that information?  I assume that because the number of Active Sessions is available in the JBoss Management Console, that there is some kind of API which can be called to return that information.

Is there any difference between the information provided in the  JBoss Management Console and the session information that would be provided by a custom class (eg: one of the samples you provided links for)?

Cheers,

Paul Hobbs

    Hi Paul!

Well the JBoss Management Console is an MBean (Management Bean) so if you know how to connect to a MBean then you could retrieve
this information :)
http://wiki.jboss.org/wiki/JBossMonitoring
http://www.informit.com/guides/content.aspx?g=java&seqNum=214
http://lists.jboss.org/pipermail/jboss-user/2006-August/007026.html

http://java.sun.com/j2se/1.5.0/docs/guide/management/overview.html
http://java.sun.com/developer/technicalArticles/J2SE/jmx.html

Hope this helps.

Regards,
    Tomas Helgi

Hi Tomas,

If I knew how to connect to an MBean it might help. Alas, I know nothing about MBeans or how to connect to them.  Also, regrettably I don't have time to spend hours learning about MBeans - my TO DO list is long enough as it is!

I am looking for a quick fix here - someone who has done something similar before (or even the same) and who is able to share their code or specific steps.  If you look at the image I attached in an earlier post, it gives you a clear idea of what I want to achieve.  The bits I need help with are steps 2 and 3.

Cheers,

Paul

Hi rrz,

Instead of using a JSP to call that class, can the class be called from a batch file?  Or even better (from my perspective) - can that class simply output the session count to a file?  I am guessing that the SessionListener class is automatically called every time a session is either created or destroyed, which is what increments/decrements the variable sessionSet.  The JSP is simply retrieving the current value stored in the variable and displaying it in a browser.  Is my guess correct?  I am not interested in displaying the session count in a browser - I want that session count in a log file.

I have found a code sample which shows me how to output a string to a file (http://www.java2s.com/Code/Java/File-Input-Output/Filereadandwrite.htm) - I am just wondering if there are any restrictions that you may be aware of?

Cheers,

Paul

Hi rrz and Tomas,

I have finally solved the problem.  Someone on another forum pointed me in the direction of the specific MBean I needed, so I wrote a little VBScript batch file which gets the activeSessions attribute from the MBean.  I have attached the code for the VBScript file.

Thanks for trying to help out.  I am happy to split the points evenly between you (if that is OK with you).

Cheers,

Paul

' Author: phobbs 
' Date: 2008/09/09
' Revision: 1.0
' Name: getSessions.vbs
' Purpose: Queries the MBean to retrieve active session count
' MBean Name:      Domain Name:    jboss.web
'                  type:           Manager
'                  host:           localhost
'                  path:           /MyApp
 
'Usage:
' getSessions.vbs
' activeSessions is output to log file D:\MyApp\log\session_count.log
' if there is an error, output to log file D:\MyApp\log\session_count_errors.log
 
'========================================================================================
 
Function GetActiveSessionCount()
 
    On Error Resume Next
 
    Const ForWriting = 2
 
    Dim strURL
    Dim log_file
    Dim error_log
    Dim fso_write
    Dim WriteFile
    Dim intStart
    Dim intEnd
    Dim htmlStream
    Dim activeSessionsBlock
    Dim sessionCount
    
    strURL = "http://localhost:8180/jmx-console/HtmlAdaptor?action=inspectMBean&name=jboss.web:host=localhost,path=/MyApp,type=Manager"
    log_file  = "D:\MyApp\log\session_count.log"
    error_log  = "D:\MyApp\log\session_count_errors.log"
    Set fso_write = CreateObject("Scripting.FileSystemObject")
 
    'get the HTML response from the URL
    htmlStream = GetHtml(strURL)
 
    'get rid of all the text between <td>activeSessions</td> and <td>Number of active sessions at this moment</td>
    intStart = InStr(htmlStream, "<td>activeSessions</td>")
    intEnd   = InStr(htmlStream, "<td>Number of active sessions at this moment</td>")
    activeSessionsBlock = Mid(htmlStream, intStart, intEnd - intStart)
 
    'replace all carriage returns, line breaks, tabs and spaces
    activeSessionsBlock = Replace(activeSessionsBlock,Chr(10),"")
    activeSessionsBlock = Replace(activeSessionsBlock,Chr(13),"")
    activeSessionsBlock = Replace(activeSessionsBlock,Chr(9),"")
    activeSessionsBlock = Replace(activeSessionsBlock," ","")
 
    'get rid of everything except the session count number
    activeSessionsBlock = Replace(activeSessionsBlock,"<td>activeSessions</td>","")
    activeSessionsBlock = Replace(activeSessionsBlock,"<td>int</td>","")
    activeSessionsBlock = Replace(activeSessionsBlock,"<td>R</td>","")
    activeSessionsBlock = Replace(activeSessionsBlock,"<td>","")
    activeSessionsBlock = Replace(activeSessionsBlock,"</td>","")
    sessionCount = activeSessionsBlock
    
    If IsNumeric(sessionCount) Then
        Set WriteFile = fso_write.OpenTextFile(log_file, ForWriting, True)
        WriteFile.WriteLine "active_sessions=" & sessionCount
    Else
        Set WriteFile = fso_write.OpenTextFile(error_log, ForWriting, True)
        WriteFile.WriteLine "There was an error"
        WriteFile.WriteLine "active_sessions=" & sessionCount
    End If
    
    Set strURL = Nothing
    Set log_file = Nothing
    Set error_log = Nothing
    Set fso_write = Nothing
    Set WriteFile = Nothing
    Set intStart = Nothing
    Set intEnd = Nothing
    Set htmlStream = Nothing
    Set activeSessionsBlock = Nothing
    Set sessionCount = Nothing
 
End Function
 
'========================================================================================
 
Function GetHtml(sURL)
 
    On Error Resume Next
 
    Set oHTML = CreateObject("Microsoft.XMLHTTP")
    'Set oHTTP = Createobject("WinHttp.WinHttpRequest.5.1")
    Set oWeb = CreateObject("InternetExplorer.Application")
    oWeb.navigate (sURL)
    oHTML.open "GET" , sURL, false
    oHTML.send
    GetHtml = oHTML.responseText
 
End Function
 
'========================================================================================
 
GetActiveSessionCount	

                                              

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