Re: Socket vs. Dataq (was: RPG, Java and Classpath practices)

Hi Aaron,

<snip>
he main issue I have with this approach (as I have done it before except

with PHP to a backend Unibasic program) is that polling takes up precious

CPU cycles, and if it is a user interactive app that means you need to be

polling every half a second or so. Get 50 users on the same app and you are

wasting a lot of CPU cycles.



Thoughts?
</snip>

At my last place we wrote an app over 5 years ago which used this mechanism to send/recieve data to/from remote systems. I was always surprised at how these systems just quickly and quietly got on with their job. I have never had an issue with speed and/or CPU usage using this method (or using DTAQs, or sockets). Although I am always vigilant - anybody who has worked with java and RPG on the system i over the years is always mindful of performance.

Granted, in an extremely volatile environment where many users require faster-than-thought responses then I would have a long hard think before using this mechanism - but I'd bench test it and see how fast it runs before throwing it out as a bad idea. In batch processes where you just want to pass data to a java app to process (classic workflow) then it is a dream to get going as the code involved is as minimal as using DTAQs but you have the flexibility of streamed data.

Regarding performance and CPU usage, I'm sure our Loviathan of a system i (which never seems to get over 20% CPU with 500+ interactive users and 1,000+ batch jobs) can handle a few directory lookups. We provide web services which perform a considerable amount of DB activity, run several dozen programs and talk back-and-forth with our tomcat servlet container/apache http server and we still have sub-second responses across the internet to our business partners.

I am offering, of course, only an alternative. Each application designer can choose the communication mechanism which seems the best fit. There is even room for combinations: a xml drop followed by an dtaq push - the java app could use the dtaq recieve wait as a timer, but a push from an app will wake it up to poll the directory immediately. This method has been used extensively and effectively in the system i batch processing architecture for years with DB tables - where the key fields are passed in the dtaq and the app uses the data to read the tables and process them. It is only a small step to replace the key fields with a xml file name and the underlying code can be changed/amended/extended without the interface needing to.

This cat can be skinned many ways, and undoubtably has been. :-)

Cheers

Larry Ducie

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