My understanding is that both WebLogic and Dynamo (and probably others)
can do the following: Each webserver has an app server plugin that
directs requests from the webserver to the appserver (If you are using
Netscape Enterprise Server, then the plugin is a NSAPI module). The
plugin is intelligent enough to direct a sessions requests to the
correct app server so that you don't need to 'stick' the user to one
particular webserver. In otherwords, if you have three webservers and
two app servers - a particular session will get tied to a particular app
server, but can use any of the three webservers; the stickiness is at
the app server level. They do this by encoding which app server to use
in the session id. Obviously if the app server goes down, they have
mechanisms for passing control to another app server.
Shashank Phadke wrote:
>
> Hi all --
>
> To add to Dave' questions, I would also be very much interested in the way
> people have tackled this problem.
>
> I havent played around with how webserver load balancing works (I am not
> sure about the word they use for that - routing ??) But I would like to know
> if anyone has tried that ? What are my options - software/hardware ??
>
> If the requests can be spread across multiple webservers, to maintain state,
> requests from a user need to be routed to the same webserver the next time.
> Can this be achieved by webservers themselves ? Its like some session info
> maintained in the webserver. If yes, then one can continue with one
> webserver <--> one servlet engine combination.
>
> If not, how do I associate a user to the particular instance of servlet
> engine ? Is there any inbuilt support for this in any of the servlet engines
> ?
>
> Writing my own session management servlet and routing servlet would be the
> last thing I would like to do ...
>
> Thanks for any inputs ...
>
> Shashank
>
> >From: David Mossakowski <[EMAIL PROTECTED]>
> >More specifically now,
> >
> >I have noted two possible set ups:
> >
> >1. Simpler round-robin algorithm to choose web server at the DNS level
> >and then have the web server load balance (with session awareness) to
> >servlet engines as it seems to be the case with Apache.
> >
> >2. Have DNS itself be session aware (3-DNS from F5) and load balance to
> >HTTP server which would have only one instance of servlet engine.
> >
> >I guess it comes down to: should one web server have many instances of
> >servlet engine on it? It seems that it is a good idea since it will
> >take much less for the HTTP server to relay request to servlet engines
> >and then send back a ready-made reply. It would seem a waste to have
> >just one servlet engine instance on one HTTP server. Is this assumption
> >correct?
> >
> >It seems that the Apache way is better. In the second approach if DNS
> >is session aware then it would send request to a given web server and
> >the web server would again have to check the session ID to direct the
> >request to correct instance of the servlet engine?
> >
> >Am I making sense here? Are there other setups? Can someone who has
> >done this share their knowledge?
> >
> >dave.
> >
> >--
> >David Mossakowski _||_ e-mail: [EMAIL PROTECTED]
> >Instinet Corporation __||||_|_||__||_ tel: 212.310.7275
> >Programmer __||||__||_|||__|||||_|__ fax: 212.583.7780
> >
> >_||__|__"I don't sit idly by, I'm planning a big surprise"
> >
> >___________________________________________________________________________
> >To unsubscribe, send email to [EMAIL PROTECTED] and include in the body
> >of the message "signoff SERVLET-INTEREST".
> >
> >Archives: http://archives.java.sun.com/archives/servlet-interest.html
> >Resources: http://java.sun.com/products/servlet/external-resources.html
> >LISTSERV Help: http://www.lsoft.com/manuals/user/user.html
>
> ______________________________________________________
> Get Your Private, Free Email at http://www.hotmail.com
>
> ___________________________________________________________________________
> To unsubscribe, send email to [EMAIL PROTECTED] and include in the body
> of the message "signoff SERVLET-INTEREST".
>
> Archives: http://archives.java.sun.com/archives/servlet-interest.html
> Resources: http://java.sun.com/products/servlet/external-resources.html
> LISTSERV Help: http://www.lsoft.com/manuals/user/user.html
___________________________________________________________________________
To unsubscribe, send email to [EMAIL PROTECTED] and include in the body
of the message "signoff SERVLET-INTEREST".
Archives: http://archives.java.sun.com/archives/servlet-interest.html
Resources: http://java.sun.com/products/servlet/external-resources.html
LISTSERV Help: http://www.lsoft.com/manuals/user/user.html
