Azure ASP (S2) swaps the CPU (NOT a scale out) and causes a high cpu, which causes the applications to hang.

Question

Azure ASP (S2) swaps the CPU (NOT a scale out) and causes a high cpu, which causes the applications to hang.

Mark Renfrew 0

The ASP appears to be "swapping" the CPU randomly, which causes a high CPU and the applications hang. We have the ASP set to a fixed number (1) at the time shown below, so this is NOT a scale out.

This also happens during the day, in which case we need to stop all the applications in the ASP, then start them again one at a time.

Question: What is the cause of this CPU swap? The tier level is S2, is Microsoft doing a hardware refresh? We cannot keep having the applications hang for no reason.

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Siva Nair 2,420 Reputation points Microsoft External Staff Moderator

2025-03-27T18:47:12.9266667+00:00

Hi Mark Renfrew,

Just checking back to see if the above response helped you to have a resolution. In case if you have any resolution, please do share that same with the community as it can be helpful to others. Otherwise, will respond with more details and we will try to help.
Siva Nair 2,420 Reputation points Microsoft External Staff Moderator

2025-03-28T15:22:34.8733333+00:00

Hi Mark Renfrew,

Just checking back to see if the above response helped you to have a resolution. In case if you have any resolution, please do share that same with the community as it can be helpful to others. Otherwise, will respond with more details and we will try to help.

1 answer

Your answer

Siva Nair 2,420 Reputation points Microsoft External Staff Moderator

2025-03-27T18:47:12.9266667+00:00

Hi Mark Renfrew,

Just checking back to see if the above response helped you to have a resolution. In case if you have any resolution, please do share that same with the community as it can be helpful to others. Otherwise, will respond with more details and we will try to help.
Siva Nair 2,420 Reputation points Microsoft External Staff Moderator

2025-03-28T15:22:34.8733333+00:00

Hi Mark Renfrew,

Just checking back to see if the above response helped you to have a resolution. In case if you have any resolution, please do share that same with the community as it can be helpful to others. Otherwise, will respond with more details and we will try to help.

Answer 1

Hi Mark Renfrew,

Lets follow some troubleshooting steps below,

Firstly Move to High CPU analysis and check if you find any alerts or error

Here you can see how many active apps are running in your plan. which instance or app is consuming more CPU and many other details.

If you find a single app is consuming High CPU then debug the app causing High CPU, Restart the bad app to mitigate the issue, scaleup the App service plan.
If you find multiple app consuming High CPU then scaleup the App service plan to the next tier, Isolate apps in their own ASP.
Enable CPU monitoring to monitor all site processes
Mitigate the issue to avoid impact to your application
collect rich diagnostic data to identify root cause within code.

Refer the below link to follow above points.

https://azure.github.io/AppService/2019/10/07/Mitigate-your-CPU-problems-before-they-even-happen.html

https://azure-advice.com/2020/11/03/azure-pro-active-cpu-monitoring/

If you have any further assistant, do let me know.

If the answer is helpful, please click Accept Answer and kindly upvote it so that other people who faces similar issue may get benefitted from it.

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Azure ASP (S2) swaps the CPU (NOT a scale out) and causes a high cpu, which causes the applications to hang.

1 answer

Your answer