Re: Rendezvous and WebObjects vs OpenJMS
Re: Rendezvous and WebObjects vs OpenJMS
- Subject: Re: Rendezvous and WebObjects vs OpenJMS
- From: David Aspinall <email@hidden>
- Date: Thu, 20 May 2004 11:24:16 -0400
Jms was and is a great technology. My issues using it for change
notification are:
- the HSQLDB database only truncates disk usage when the service is
restarted. In a high volume deployment this grows very large over one
day (while not a disk issue it does slow things down .. or at least
seems to). I could use a SQL database but that seems to defeat the
purpose of not having a database fetch involved in the CN. Also, given
the volume, do I really want that load on my business system? My
answer might be different if the messages were not so ephemeral.
- sending change snapshots is very efficient in small numbers (each
interested application can incorporate the changes without having to
incur a fetch) However, in high volume with several applications the
Jms can really fall behind and be out of date. I did not size the
messages, but if the growth of the HSQLDB is an indication it was a
problem. Realistically only 2 - 3 instances are interested in the
changing values of any particular record. Very little data in our
system is public to all users, but there are several collaborative
areas where it is important to be in sync.
- so we switch to passing only EOGlobalId's which is more efficient
from a messaging side and not that bad on the recipient side. Each
recipient (client) checks the database context snapshots. If the
object has a current snapshot then the record for that EOGlobalId is
forced to refault, but does not fetch until needed. So if the user has
gone away or does not navigate to a page needing that record, then it
is never refetched.
So that is where we are now, small specific messages over OpenJMS, with
cron jobs to force an OpenJMS restart every night. The final issue is
with OpenJMS stability in multiple deployments. We use Windows 2000,
Mac, RedHat and Debian. The windows service is the one I am least
happy with (that may just be my natural aversion to all things M$oft),
but the service disappears on all deployments periodically. I could
write a guard script that would auto-restart OpenJMS if it dies, but I
am thinking UDP Multicast or non-deterministic grid style
communications would be better.
Just my $0.02
David
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(416) 513-9524 x263
Ticoon Technology Inc.
56 The Esplanade, Suite 404, Toronto, ON, M5E 1A7
On 20-May-04, at 3:34 AM, Sam Hart wrote:
David wrote:
For the past year we have been using openJms for change notification,
but we are not 100% happy with the results. I wont go into the issues
here
thats a shame, I am keen to know what problems you are seeing
or what issues it is creating for you.
but I am experimenting with options.
I spent a lot of time trying different options out before I settled on
messaging.
I am however looking at some point replacing OpenJMS with another free
JMS which appears more stable.
My question is: does anyone have good or bad experiences using
Rendezvous (ZeroConf) with WebObjects applications?
I have used multicast based change notification before, didn't rate it.
It's far too flakey compared to messaging.
S a m
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