Hi,
as far as I know WAS 3.0/3.5 does. You can turn a switch and Websphere
will synchronize every http session access accross the cluster using the
underlying database. This results obviously in a huge performance penalty.
I don't remember WAS having a switch to tell it, that it is being used
with a session-aware dispatching mechanism. You can just use the switch to
synchronize state/lock with the database. As far as I remember it is called
something like use in a cluster. A working in a session-aware
environment switch could be nice for JBoss in order to prevent all the
overhead involved in locking, when only one node is accessed anyway.
Just for the sake of the full picture. I rememeber that everytime you
access the http-session a lock is created and when you leave the service
method the lock is released. IBM provides also an interface with a method
sync() to release it earlier.
I haven't worked with Websphere for more than a year now (being 3.5 the
last version I was working with), but I don't think that they found the
silver bullet and I assume it is still working that way, but don't know for
sure. Anyway my knowledge is not sharp as a pencil anymore, maybe I got some
of the details wrong.
Mariano
-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of Sacha
Labourey
Sent: Saturday, December 29, 2001 10:24 AM
To: Bill Burke; Jboss-Development@Lists. Sourceforge. Net
Subject: RE: [JBoss-dev] HttpSessions: distributed locking
Bill,
That is really interesting.
Furthermore, for BEA, remember that thanks to their front-end dispatcher, it
is always the same server that will receive the invocations (until it
fails). Consequently, they don't need distributed locking because until a
server dies, there is no distributed state anyway (I mean state that is used
on different nodes, state is only replicated but replicas are not used)
Cheers,
Sacha
-Message d'origine-
De : [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]De la part de Bill
Burke
Envoyé : vendredi, 28 décembre 2001 22:14
À : Jboss-Development@Lists. Sourceforge. Net
Objet : [JBoss-dev] HttpSessions: distributed locking
Weblogic doesn't seem to support concurrent access to clustered
HttpSessions. Maybe it is all right for us to be this lazy too.
Applications Using Frames Must Coordinate Session Access
If you are designing a Web application that utilizes multiple frames, keep
in mind that there is no synchronization of requests made by frames in a
given frameset. For example, it is possible for multiple frames in a
frameset to create multiple sessions on behalf of the client application,
even though the client should logically create only a single session.
In a clustered environment, poor coordination of frame requests can cause
unexpected application behavior. For example, multiple frame requests can
reset the application's association with a clustered instance,
because the
proxy plug-in treats each request independently. It is also
possible for an
application to corrupt session data by modifying the same session
attribute
via multiple frames in a frameset.
To avoid unexpected application behavior, always use careful planning when
accessing session data with frames. You can apply one of the following
general rules to avoid common problems:
In a given frameset, ensure that only one frame creates and
modifies session
data.
Always create the session in a frame of the first frameset your
application
uses (for example, create the session in the first HTML page that is
visited). After the session has been created, access the session data only
in framesets other than the first frameset.
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