App Service Plan - Periodic Spikes

Udayasri Bhushan 25 Reputation points
2026-08-14T08:22:32.32+00:00

Additional Issue – Periodic CPU Spikes on App Service Plan

We are also observing regular periodic CPU spikes on our Azure App Service Plan.

Environment

  • App Service Plan: te*********
  • SKU: P0v3
  • OS: Linux
  • Application Type: Web App for Containers
  • Always On: Disabled
  • Health Check: Not configured
  • Application/API traffic: No API requests are occurring during the observed spikes

Observation

The App Service Plan CPU usage shows a highly recurring/periodic CPU usage pattern.

Under normal conditions, CPU usage is generally around 3–10%, but we are observing periodic spikes, with some spikes reaching approximately 23–24%.

The spikes appear to occur at regular intervals, even when there is no corresponding application/API traffic.

We have verified that:

  • Always On is disabled
  • No Health Check is configured
  • There are no known scheduled jobs or application operations running at the time of the spikes
  • No API requests are hitting the application during the observed spikes

The attached Azure Monitor screenshot shows the recurring CPU pattern over the last hour.

Question

Could you please help us determine the cause of these periodic CPU spikes?

Specifically, we would like to understand:

  1. Could these spikes be caused by Azure App Service platform/system processes, container management, monitoring, worker management, or other platform-level operations?
  2. Does Azure App Service perform any periodic operations that could cause CPU consumption on a Linux Web App for Containers?
  3. Since Always On is disabled, no Health Check is configured, and there is no application/API traffic during these periods, could these spikes be related to container startup, warm-up, recycling, platform health checks, or other App Service platform activity?
  4. Is there a way to identify which process or component is consuming CPU during the exact time of these spikes?
  5. Is this CPU pattern expected behavior for a P0v3 Linux Web App for Containers, or should we investigate this as an application/container-level issue?

We would particularly like to understand why the CPU usage follows such a regular periodic pattern, including spikes up to approximately 23–24%, despite there being no apparent application traffic at those times.

The attached Azure Monitor screenshot shows the CPU Percentage metric for testgen-asp-container over the last hour.

Attached the image for your reference.

Thank you.Screenshot 2026-08-14 124853

Azure App Service
Azure App Service

Azure App Service is a service used to create and deploy scalable, mission-critical web apps.

1 answer

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  1. AI answer

    2026-08-14T08:23:01.09+00:00

    Yes—some CPU usage can come from activity outside the application itself, and a difference between plan-level CPU and app-level CPU can indicate CPU consumed by system or kernel activity rather than only the app process.

    For Azure App Service, the supported way to investigate periodic spikes is:

    1. In the Azure portal, open the App Service.
    2. Go to Monitoring > Metrics.
    3. Add CPU Time and CPU Percentage for the App Service Plan.
    4. Check whether the spikes align with any other metric changes.
    5. Open Diagnose and solve problems and run High CPU Analysis for an automated assessment.
    6. Also review HTTP Requests Analysis or the Requests metric to confirm whether the spikes correlate with request volume.

    To identify what is consuming CPU during the spike window:

    1. Open the Kudu console for the app: https://<your-app>.scm.azurewebsites.net
    2. Go to Process Explorer.
    3. During a spike, inspect the worker process.
    4. Collect a Full Dump from w3wp.exe, or enable Collect IIS Events and click Start Profiling.
    5. Reproduce or wait for the spike, then stop profiling.
    6. Analyze the resulting trace in Visual Studio or PerfView to find the CPU-intensive code path.

    What the available guidance supports:

    • High CPU can be caused by application code paths such as tight loops, heavy serialization, expensive regular expressions, sitemap generation, or report generation.
    • If slowness or spikes correlate with increased request volume, scaling out or enabling autoscale is recommended.
    • If CPU is consistently higher than expected, scaling up or scaling out the App Service plan is also recommended.
    • Overall CPU can exceed the sum of app CPU because system or kernel services are included in overall CPU usage.

    What is not established by the available guidance:

    • No supported statement is available here that confirms a specific periodic Linux App Service platform task, container-management cycle, warm-up cycle, or health operation as the cause of the recurring pattern you observed.
    • No supported statement is available here that says this exact recurring 23–24% pattern is expected behavior for a P0v3 Linux Web App for Containers.

    Based on the supported guidance, this should be investigated first as a CPU-consumption issue by measuring plan metrics, checking request correlation, and capturing a dump or profiler trace during the spike to determine whether the CPU is coming from the app workload or from non-app/system activity visible at the plan level.

    References:

    AI-generated content may be incorrect. Read our transparency notes for more information.

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