Hi Laird,
This depends heavily on your servlet engine implementation. WebLogic's
implmentation offers several ways to use sessions across multiple
servers in a cluster. Through file persistence, JDBC persistence, and
in-memory session replication you can have many servers answering
requests and ensure that sessions are uniquely tied to a particular
user and that if one of the servers goes down you will not lose the
session information.
As for scalability, in-memory session replication is the way to go.
In this configuration no session information is persisted, instead
updates are routed to pairs of servers. This can be an order of
magnitude faster than actual hard persistence and gives you very
similar reliability. Because of our use of server pairs you can
also scale this up to large numbers of servers without increasing
the overhead.
As I said before though, with other JSP engines YMMV.
Good luck,
Sam
> >This probably ultimately concerns servlets, but it applies to the session
> >scope of JSP pages as well.
> >
> >I've heard from several sources now, who have not gone into details, that
> >relying on the builtin Session object will get you into trouble when your
> >high-volume web application begins getting pounded. Specifically, the
> >problems referred to had to do with load balancing (presumably
> there would
> >be a problem matching outgoing responses with their incoming requests).
> >
> >Can anyone comment on these problems in general? Should I assume that I
> >will have to write my own centralized session management so that I can
> bring
> >up more than one JSP engine at a time?
> >
> >Cheers,
> >Laird
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