• From: Len Bullard <len.bullard@u...>
• To: Jonathan Robie <jonathan.robie@r...>
• Date: Wed, 8 Aug 2007 16:23:16 -0500

Ok, I will reveal my massive ignorance but that's fine.  I was considering
the tradeoffs between querying the database to find anything new versus
polling the directory and having the database publish when it changes since
it will know.   The question seems to turn on where the most cycles are
being consumed: polling and file i/o vs querying on a scheduled basis.   In
ASP (another MSThrall gig), there are timers for refreshing a control so
hooking that up and querying is quite easy even for me.  OTOH, RSS readers
also handle that nicely.

I am somewhat stuck with the solutions I proposed, but for the sake of
learning and keeping signal high here on the big list, why is a messaging
system better?  

len

(Personal Note:  It is good to be back on the ground level of software
instead of schlepping answers back and forth among writers and managers in
the executive suites.)

From: Jonathan Robie [mailto:jonathan.robie@r...] 

Hi Len,

I think of both feeds and SQL queries as pull technologies - the user 
checks the feed to see if there's anything new, or does a query to see 
if there's anything new.

For this kind of push application, I'd be more inclined to use a 
messaging system that has both guaranteed delivery and really good 
performance. One of my current hobby horses is the AMQP protocol, which 
will be supported by Red Hat Messaging, an open source implementation 
for enterprise level applications. Early versions are available to 
download and play with.

Check it out here:

http://labs.jboss.com/rhmessaging/
http://rhm.et.redhat.com/page/Getting_Started_With_RHM

Jonathan
 
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