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We have a DNN site running 9.1.1 we have been experiencing problems for a while where the IIS service will consume all available resources from the processor and make the site unresponsive. The issue will often resolve it self given time, but the amount varies from almost instantly, to hours. This problem has been occurring for quite some time. There doesn't seem to be anything in the log files about it, and DNN support hasn't really been able to help. This is probably a little vague but I'd be happy to answer any questions if anyone has any thoughts.

bwassink
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  • "DNN support hasn't really been able to help", so what did they do? I wonder with all source code available, hang dump analysis can easily show what's up. – Lex Li Feb 24 '20 at 18:41
  • Mainly looked at logs, we sent them backups of our front and back end and after a couple of weeks they asked us to change some settings in IIS. It had no effect on the issue. – bwassink Feb 24 '20 at 19:51
  • @bwassink: I assume you've enabled performance monitoring to log resource utilization. Does the resource utilization build up slowly over time, or does it get pegged immediately upon a certain event? If the former, is there a correlation with your overall traffic or web requests? If the latter, are you able to isolate it back to a specific action or request type? – Jeremy Caney Feb 24 '20 at 20:06
  • As you acknowledge, unfortunately, this probably won't provide enough details to help us offer much meaningful direction. Problems like this could be due to code, they could be due to IIS configuration, they could even be due to other modules in use. This problem may also be better suited for [Server Fault](https://serverfault.com/) since it'll likely require investigation via performance monitor and IIS logs, as well as adjustment via IIS itself. – Jeremy Caney Feb 24 '20 at 20:12
  • Have you reviewed dump file? We need to figure out what method or exception caused this issue. Then find try to find the root cause. Log file may not work in this case. – Jokies Ding Feb 25 '20 at 09:55

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There are a lot of things that could be related to this, but there are some common culprits with the behaviors that you have noted.

  • DNN Scheduler - Search Indexer - This can get "behind" or do some funny stuff. When the site is pegged see if this one is running
  • Purge Scheduler History - Check the size of the "ScheduleHistory" database table, if large the purge of this table could be causing this
  • Purge Event Log - This could be similar to that of scheduler history as noted below

Barring these, diagnostic traces etc will be needed and without a bunch more information cannot easily be answered via this medium.

Mitchel Sellers
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