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ecthomas's avatar
ecthomas
Occasional Reader
Sep 12, 2025

Mysterious Nightly CPU Spikes on App Service Plans (22:00-10:00) Despite Low Traffic

For several months now, all of our Azure App Service Plans have been experiencing consistent CPU spikes during off-peak hours, specifically from approximately 22:00 PM to 10:00 AM. This pattern is p...
App Services
azure
monitoring
Kidd_Ip's avatar
Kidd_Ip
MVP
Sep 13, 2025

Please try this

 

1. Enable App Service Diagnostics
Go to App Service > Diagnose and Solve Problems > Availability & Performance > High CPU Analysis. This tool pinpoints top resource-consuming requests and threads.

2. Use Azure Monitor CLI
Run:

az monitor metrics list \
  --resource /subscriptions/<subid>/resourceGroups/<RG>/providers/Microsoft.Web/sites/<AppName> \
  --metric "CpuPercentage" --interval PT1M

 

This gives minute-by-minute CPU data to correlate with other logs.

3. Profile with Application Insights
Turn on the Profiler to capture snapshots during the spike window. Flame charts can reveal inefficient code paths or unexpected calls.

4. Check for External Traffic
Use Network Watcher or App Gateway logs to detect unexpected inbound traffic.

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