RE: Problem with session ojects: memory size, updates

["Jesse Alexander (KADA 11)" <al...@csfs.com>]

Hi Sandra,

I prefer to remove the objects from the session as soon as I can 
declare that they are not usefull anymore.
EG.: In action_1 I build a model-object, use it in jsp_1 and
process the users action in action_2. If the usecase is finished here,
I remove the object from the session.

As for session size: The 4kB recommendation comes from servers that
support clustering. Because the session must be propagated to all
members of the cluster, it should be kept as small as possible.
We have a few application running with substantial numbers of concurrent
users that can have up several megabytes of session-data. If the usecase
needs it, do it. Often we have the case that a few users need lots of 
session data, and most users just a few bytes...
Ok for us session-data is used, because our persistance level is on a 
CORBA-backend host and we have no jdbc on our midrange. Therefor we 
calculate it is cheaper to a few Gig of memory to our servers in order
to save on network-data-transfer.

hope this helps
Alexander

-----Original Message-----
From: Heligon Sandra [mailto:Sandra.Heligon@nextream.fr]
Sent: Freitag, 12. Juli 2002 13:11
To: 'Struts Users Mailing List'
Subject: RE: Problem with session ojects: memory size, updates
Importance: High


Thanks John for your response,

I have already read the message
http://www.mail-archive.com/struts-user@jakarta.apache.org/msg34592.html
but I would like to have more details with real examples. 
I believe that the best way is to try.
I read that objects in the session must be removed unlike the request
objects. 
Is it good to do that when the application invalidates the session ?. 
Because we save objects in the session in order to access data during all
the session life.  

I would like to have advices or tricks for updating and looking up session
objects (JavaBeans and not EJB).
Imagine I have the following business objects model:

Class A composed of several instances B, each B item can be composed of
several C instances. (nested beans).
If the list of each sub-beans is variable, must I use dynaBean ? 

Imagine the user make a request about the instance B2, I get data
information
and store the JavaBean B2 in the HttpSession.
Later the user makes an other request and the B4 instance is required, I
store
B4 in the HttpSession.

Then two problems:
1. The last request needs to get A instance, I get A1 but before saving A1
I have to test if A1 is composed of B4 or/and B2 in order to remove objects
from
the HttpSession. Then I store A1 in the HttpSession.
It is very complicated, isn't it? What are the others solutions to store and
look up "nested beans" ?

2. The WebServer receives a data change notification, in this case how can I
look up all active sessions and all session objects of each session to
update
the JavaBeans which changed?
How must I do to be sure that Actions or JSP pages don't access data during
update?

Thanks
Sandra

-----Original Message-----
From: Jon.Ridgway [mailto:Jon.Ridgway@upco.co.uk]
Sent: 12 July 2002 11:47
To: 'Struts Users Mailing List'
Subject: RE: Problem with session ojects: memory size, updates 


Hi,

Your English is a hell of a lot better than my French...Your question is one
that comes up a lot on the list try a search at:

http://www.mail-archive.com/struts-user@jakarta.apache.org

for 'session size'. One pertinent post is:

http://www.mail-archive.com/struts-user@jakarta.apache.org/msg34592.html

In short, the answer to what should go in the session depends on how your
application will be used. If you expect a *very* high number of concurrent
users your session should be under 4k (taken from iAS, WebLogic and
WebSphere docs, white papers etc). 

It will also depend on your hardware, how much RAM is available, network
bandwidth, database size/speed etc. If you can predict the highest level of
concurrent users, multiple your maximum session size by this. The result
will be the amount of RAM taken up by all the sessions put together, if you
have sufficient RAM to handle this and all over requirements, then the
session size is not an issue.  Note however that the number of users can
explode unexpectedly, so the best practice recommendation is to keep session
size as small as possible. 

As for the speed of looking up objects from the session, this will depend on
your app server, when clustering some app servers will store the session in
a db or other persistent store, lookups in this case are relatively
expensive. If you are not clustering, I wouldn't worry about the speed of
the lookup (even if you are I wouldn't worry about it that much - its not a
bottle neck I've ever come across.)

Jon Ridgway


-----Original Message-----
From: Heligon Sandra [mailto:Sandra.Heligon@nextream.fr] 
Sent: 11 July 2002 15:12
To: 'struts-user@jakarta.apache.org'
Subject: Problem with session ojects: memory size, updates 


	Sorry, my english level isn't very good.

	I read that the Struts framework doesn't make (oblige) 
	to use one particular model implementation (EJB, JavaDataObject,
JavaBean, ...).
	But the JavaBean solution is understood or greatly recommended,
isn't it ?
	Because struts uses JSP to display data and JSP pages use JavaBean
tags.
	If  we work whit XML representations of  remote business objects, is
it better to
	use struts XSL tags rather than generate JavaBean from the XML
description ?
	The XSL solution requires to know XSL tags and  is slower and more
complex.
	With JavaBean solution I am frightened having memory or request time
	problem.
	The user does a request, the selected Action gets business data from
the
	enterprise tier, generates one or several JavaBean instances and
stores the JavaBean 
	in the HttpSession. 
	But the HttpSession size will grow quickly.
	It is difficult to know when we have to store data in request scope
or session scope.
	Has somebody advices about this dilemma? 
	I am tending to put data systematically in HttpSession in order to
reduce network traffic if the user
	ask again this page.
	What is the max size of the session objects ? 
	If we user rights on the business objects, we will have the same
	JavaBean in several HttpSessions.
	What do you think about this problem ? 
	
	A last question if we have numerous session objects, when we will
have to update one
	of them it will be very slow to find it in the list.
	Do you have advices about that ?
	Is the JavaBean/HttpSession solution realistic with "real-time"
data?

	Thanks a lot in advance. 
	
	 
	

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