My last big Azure problem: The unexplained CPU spike

Over the last year and change, I've written a number of posts about the challenges around moving my sites (primarily CoasterBuzz and PointBuzz) to Azure. These are moderately busy sites that can for the most part live in a small websites, er, app service, instance, with SQL Azure S0 for the data, some storage here and there, queues, and some experimental use of search, Redis and what not. I know I've done some complaining, but only because I really want one of the core premises of the cloud, namely for all of the maintenance and backend stuff to be abstracted away, to deliver without me thinking about it. Mostly, it has.

But I've got one more thing that I see every now and then, maybe once every two months, that crops up that I can't explain. Specifically, one of the sites will start showing a ton of CPU time, which of course slows the other one as well. To be perfectly honest, sure, it could be something in my code, but I would expect to see some other indicator that had some correlation. Memory usage doesn't increase, there's no associated traffic spike, and it's so infrequent that it seems weird that anything I'm doing would cause it. The resolution is simple enough: restart the app with the CPU spike.

I don't want to just blame the platform, but I'm not sure where else to look at this point. A memory dump doesn't show anything out of the ordinary.


  • Did you ever work this out? My site also spikes to 100% sometimes sending the site down and users screaming. I recycle and it is fine. Memory, requests, everything else is normal.

  • Nope. Still no resolution.

  • My site spiked yesterday to about 90% and my site was so slow and my clients started calling me. I changed to the next higher pricing tier and noticed that the CPU went from 90% down to 14% after the change. Kept it there for an hour while I let me clients get some work done, then I downgraded the pricing tier back to where it originally was. Now it's hovering around 30% like normal. I don't know what happened.

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