----- Original Message -----
Sent: Tuesday, July 17, 2001 6:01
PM
Subject: RE: Clustering..
<snip>
This mechanism have one
drawback: If you keep an object in session and later some place you get
the reference of the object and modify the object the modifications won't get
reflect across islands:
Example:
UserInfo info = new UserInfo() // Some kind of
object...
info.user_name = "oldName";
session.setAttribute("UserInfo", info) // At this point the info is
replicated to all cluster islands
//Later at any place of your code
UserInfo info =
session.getAttribute("UserInfo");
info.user_name =
"newName"; //This change won't replicated
//In some other program
UserInfo info =
session.getAttribute("UserInfo");
System.out.println(info.user_name) // If the request comes to the
same cluster where the modification occures you will get the "NewName" if the
request goes to another cluster you will get "oldname"
Work Around: If you do any kind of modifications to your
session objects put the objects again into session using
setSessionAttribute. Keep one thing in mind that when ever you call this
setSessionAttribute method the session info is going to replicate across
different islands.
<MS>I've noticed this too, is this according to
the jsp/servlet specifications or just container specific? When you are using
JSP's it is very awkward having to call setAttribute() after every
<jsp:setProperty name="myObject" property="*" /> or
similar.
This is the same problem which I faced and lead me to write my
own session management.
Kesav Kumar Kolla
Voquette Inc
650 356 3740(W)
510 889
6840(R)
Voquette...Delivering Sound Information
-----Original Message-----
From:
[EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On
Behalf Of Duffey, Kevin
Sent: Monday, July 16, 2001
12:39 PM
To: Orion-Interest
Subject: Clustering..
Hi all,
I know how to cluster Orion..after all, its pretty easy. What
I want to know
from someone who knows..is if in the
1.5.2 version all the bugs (if there
were actually
any) are worked out. Does Orion cluster with no problems? Does
session fail-over and application context fail-over work
without a hitch
(providing all objects in the session
and/or context are serializable)? If
you have two
machines in an island, and the session begins on one..does it
automatically "copy" any session info to the other box for you? If you
shut
that box off, and all requests go to the 2nd box,
does the session still
exist with all objects still in
memory?
I take it each and every request on a clustered box requires
the session to
be duplicated exactly as is to the
other machine? If this is the case, at
what "rate"
does Orion copy out the session and anything else to another
server in the island (or to each and every server in the island)? How
does
this affect performance as compared to using just
a single box without
clustering..is it 2 to 3 times
slower because of not only copying its
session to one
or more boxes, but also having to deal with "merging" other
boxes context/session information into its own? Or does a cluster
simply
create the objects and session stuff on each
box as its generated (thus..its
not some background
thread that copies session info when it has time to
other boxes)?
Is it equally good at clustering on the EJB tier (so
scalability on the EJB
tier or the front-end WEB tier
is equally as easy)?
Thanks.
