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| My Trigger App Works but I Still Have Questions |
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| PeterWillis |
 Posted: Tue Jan 27, 2004 12:22 pm Post subject: My Trigger App Works but I Still Have Questions |
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Newbie
Joined: 27 Jan 2004
Posts: 1
Location: Regina, Saskatchewan
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I have some general questions regarding triggers.
1) I have read Chapter 14 in the App Guide and also many posts on this forum. Tweaking some of the CSD05 sample IBM apps and some trigger demos I linked to from this site (thanks Jorgen) I have a working trigger scenario on Win2k, where I am kicking off a .NET app from an input.queue/init.queue configuration. The trigger type is set to 'first', and my trigger process app reads all messages through to 2033 (no more messages). Seems to work pretty slick, but since its my first attempt I would like to clarify the concepts with the experts, especially regarding trigger interval.
Many posts on this site recommend trigger type of 'first'. 'First' works in conjunction with '2033'. 'First' means that there will be a trigger event only if depth goes from 0 to 1, EXCEPT if the queue is open for input, because the assumption is that there is already a process at work on the queue which should handle ALL the messages on the queue. So if there is more than 1 message or the queue is open, the already-running app must handle the new message by running through to 2033, therefore a trigger is not required. To be safe, the triggerinterval should be set to something like 60 seconds, which will ensure that a new trigger process kicks off if something bad happens to the first trigger app which is assumed to be running. All of this is a balance between the rate of messages and the time it takes the trigger process to read/handle/delete them. Does this sound right?
2) Somewhere on this forum (but I can't find the post  ) a comment was made regarding triggers not being the best solution for high load/high performance scenarios. Is this true? What other solutions are available? What would consitute 'high loads'? Would this be because of the overhead in starting/stopping new trigger apps?
3) I'm wondering what experiences anyone might have had (good or bad) with using the CSD05/.NET code in a setup as I describe.
This forum is invaluable and I appreciate the time spent by folks who post.
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Thanks, Pete |
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| jefflowrey |
| Posted: Tue Jan 27, 2004 12:29 pm Post subject: |
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Grand Poobah
Joined: 16 Oct 2002
Posts: 19981
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Yes, there is a high load for repeatedly starting an application. This is why triggering is not recommended for high-volume applications. It's also not recommended for applications with frequent, but dispersed, small groups of messages (ten messages every minute, for example).
The other option than triggering is to write a listener app. A listener app is one that runs all the time, looping over a Get that has a WAIT interval. A Wait interval will expire as soon as a message shows up - so the app doesn't have to wait the full interval time.
Typically, regardless of the pattern of your incoming messages, you'll set the wait interval fairly small. This is so that your app can respond quickly to shutdown events (like FAIL_IF_QUIESCING). So in the case of ten messages every minute, you might set your interval to 30 seconds. Your app would then get messages as often as they showed up, but could still be shut down very quickly (once an outstanding wait had expired).
Everything else you have written sounds reasonable.
And I havne't worked with the .NET frameworks.
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I am *not* the model of the modern major general. |
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