What could be causing a large increase in the socket connections of our App Services?

Question

In the last couple of days, we have seen a structural rise in the number of socket connections for each of our App Services. These App Services run behind an API-Management service instance. However, we do not see a structural rise in the number of requests we receive on our Application Gateway (which is in front of the API-M instance).

This started last Monday evening to Tuesday morning. We have no explanation for this as we did not change anything in that timeframe.

Below are the metrics of the past 7 days.

Thank you for any help you can provide!

Answer 1

Hi Lloyd | Boxplosive,

We observed a steady increase in socket connections for your App Services from Monday evening (April 14) to Tuesday (April 15), but the request volume at the Application Gateway remained steady. Possible causes include longer open connections, new code opening more connections, App Service scaling adding more instances, Azure managing connections to prevent source network address translation (SNAT) exhaustion, or a connection leak.

• Check recent deployments for any code changes made around Monday evening, even if they seem unrelated.
• Make sure all connections and resources are properly closed, use connection pooling, and dispose of resources correctly.
• Check App Service logs and diagnostics, enable diagnostics, look for exceptions in Application Insights, and review worker process restarts.
• Optimize connection management by using persistent connections, connection pooling, retry policies with circuit breakers, and HTTP/2 to reduce overhead.
• Check for dependency issues by reviewing changes in external services your app relies on and monitoring connection timeouts and response times.

Please refer to the document below for troubleshooting outbound connection errors in Azure App Service.

Troubleshooting intermittent outbound connection errors in Azure App Service - Azure App Service | Microsoft Learn

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