Re: XML Feeds vs SQL Queries
Hi Len, Here are some reasons that a messaging system might be better for this kind of application: 1. Updates are made precisely when something has changed at the source. This eliminates the need for clients to poll just in case something has changed, which accounts for a lot of unnecessary polling. 2. Guaranteed delivery is supported. 3. Higher performance network protocols can be used. I think the existence of open source, high performance, reliable messaging systems has the potential to significantly change the way people write a lot of systems, including a lot of XML-based systems. This is one of the reasons I'm at Red Hat now. Jonathan Len Bullard wrote: > 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 > > This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. If you have received this email in error please notify the sender. This message contains confidential information and is intended only for the individual named. If you are not the named addressee you should not disseminate, distribute or copy this e-mail. > >
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