The extensive use of @Persist("flash") for form fields could cause thrashing
in an app cluster. That's one piece I'd like to see refined in Tapestry to
be one in a different way.
----- Original Message -----
From: "Howard Lewis Ship" <[EMAIL PROTECTED]>
To: "Tapestry users" <users@tapestry.apache.org>
Sent: Monday, September 08, 2008 12:59 PM
Subject: Re: Tapestry App Replication
Tapestry is designed to be "a good citizen" of an application server
that supports clustering. It's careful about what it writes into the
HttpSession. The framework understands that the server that receives
a request may not be the same one that rendered the page initially;
this knowlege affects many code paths, and the approach Tapestry takes
to caching and pooling page instances.
Your part is to properly manage the objects put into the HttpSession
(via @ApplicationState or @Persist). These objects should be
immutable where possible (i.e., String, or a primitive or wrapper
type). For @Persist, if you change the internal state of a mutable
object, you should reassign the field, to ensure that Tapestry knows
to update the HttpSession (and force the value to be serialized and
distributed around the cluster).
Still, sticky sessions are the way to go when possible. Much more
efficient use of resources ... you are scaling *out* not *up* which is
always cheaper.
Again, Tapestry is a good citizen, but from the application server's
point of view, it's just another servlet application. The heavy
lifting here is application server specific.
On Mon, Sep 8, 2008 at 4:44 AM, Carl Crowder <[EMAIL PROTECTED]>
wrote:
Hi all,
Is it possible to run multiple instances of a Tapestry app on various
servers, but have them share session and application state?
Carl
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Howard M. Lewis Ship
Creator Apache Tapestry and Apache HiveMind
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