Thursday, May 30, 2013

Slow response IIS with long running requests

Last week i got myself in a little trouble. I have a back-end website that does a lot of processing stuff with very long running requests (some take days to complete). The website got slow if about 8-9 long running requests were active. These request do not consume a lot of cpu or memory so the problem had to be somewhere in IIS or Coldfusion. I posted a blog about the maximum number of simultaneous templates in coldfusion earlier this month (maximum number of simultaneous templates). Although this could have been an issue here it was not. In the IIS application pool each pool has 1 worker process assigned to it by default. In most cases (read 99%) this is fine, but if you are working with multiple long running request this can become a bottleneck. To resolve the problem you can assign more worker processes to the application pool.
Note: In general it is not a good idea to increase the number of maximum worker processes. This should only be done in very specific circumstances.

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