Session Replication

[Annamaria Joseph]

My application has two Application servers, App1 and App2..

we are using weblogic 8.1 Application server

There is session replication done in weblogic.xml file .

<session-descriptor>
<session-param>
<param-name>InvalidationIntervalSecs</param-name>
<param-value>1</param-value>
</session-param>

<session-param>
<param-name>PersistentStoreType</param-name>
<param-value>replicated</param-value>
</session-param>


The application works fine but currently there is data getting replicated among different users.

Is it the problem of session data getting merged with other session data
or is it server cache not getting cleared or is there any setting to be changed in weblogic application server??

or is there any other problem ???

Kindly reply with solution...

[William Brogden]

I think it very likely that somewhere you are improperly using an instance variable that can be "seen" by all request threads for user data.

Bill

[Prince Manchanda]

Can you post some examples of the data that is getting replicated.

The application works fine but currently there is data getting replicated among different users.

Also, would recommend that you check for static variables in your Servlet. They are known to create problems, in my experience.

[Annamaria Joseph]

Thank you for your valuable responses.

# The values are private variables and they are accessed using setter getter.

and then

req.setAttribute(private variable)
req.getAttribute()

is used.


# Instance or static variables are not used, meaning value to the variables is not directly assigned.


Merging is such

First entry :100000739222|643990|171.00|

Second entry : 100000739222|643991|113.00| ....... wrong entry

100000739222 is a unique entry and should had not been duplicated.. ideally.

100000739223|643991|337.0| .... should had been the right entry.


first entry got merged to some other entry.


#Is it session data getting merged??

Is there any solution for it...

Please reply.

[Bear Bibeault]

Perhaps you should show us the code?

[Annamaria Joseph]

I just observed this in the code..

private HttpServletRequest req;
private HttpServletResponse res;


public void doPost(HttpServletRequest req, HttpServletResponse res)
throws java.io.IOException, ServletException {
try {
this.req = req;
this.res = res;
}

Is this instance variables?

if it is a instance variable, then can you tell me how does instance variables affect in the session replication?

and what is the solution for it?

[Ulf Dittmer]

Yes, req and res are instance variables. But it makes no sense to store references to those objects - what are you trying to achieve by that?

[Annamaria Joseph]

Its an old code developed by someone using weblogic 8.1.

The instance variable is used to keep the variable accessible outside the post method. So that the same variable can be used in other methods too.

How does instance variable affect in session replication? just trying to understand it..

please help.

[Ulf Dittmer]

There is no direct connection between session replication and instance variables. Stuff like servlet requests/responses can't be replicated, though (they're not serializable), but that's OK because it makes no sense to put those in the session anyway.

[Annamaria Joseph]

Is this a common problem existing in weblogic 8.1?

[Bear Bibeault]

In any servlet container you should not be using servlet instance variables.

[Abhay Agarwal]

Any instance variables defined in Servlet shall be shared by all threads. Any servlet container share same Servlet object across all threads. Threads keep its value on Stck but Servlet is stored in Heap. So means that instance variables of Servlet are seen by all threads using that servlet. In your case, probability is that one thread has assigned that unique id but that thread was not able to complete it work as OS system has deferred that thread execution and started another new thread. That new thread used same unique ID.

[Annamaria Joseph]

Thank you everyone for your valuable inputs.

[Annamaria Joseph]

Instance variable must be a reason.

But we have deployed a patch provided by Weblogic for Weblogic 8.1 and the problem is currently solved.

Thank you each and everyone..