Function app trigger log availability to customers

Janne Kujanpää 196 Reputation points

Consumption Function app SLA states following:

“Unavailable Executions” is the total number of executions within Total Triggered Executions which failed to run. An execution failed to run when the given Function App history log did not capture any output five (5) minutes after the trigger is successfully fired.

Is there any way customers can see the incoming triggers(in our case HTTP request) if

  • all app insights tables are empty when failure happened
  • and function app diagnostic log tables is empty when failure happened
  • and even metrics are empty when failure happened

It looks like some layer returned HTTP 503 and nothing in function app side indicates that there was failed request. The question: Where is the list for "after the trigger is successfully fired" in this case?

Azure Functions
Azure Functions
An Azure service that provides an event-driven serverless compute platform.
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  1. Ryan Hill 26,856 Reputation points Microsoft Employee

    Hi @Janne Kujanpää

    If you are seeing 503 errors in your function app, you can check the function app's metrics and logs to investigate what may be causing the high load. You can see these metrics under the Monitoring tab of the function in the portal.

    From the context of you question though, the 503s could be occurring on/at the front-end worker. And since the Consumption Plan automatically scales out, there may be an issue during that operation if you're seeing it consistently. One option to consider is scaling out the function app on a higher tier to handle the load and see if that resolves the issue. If it does, you can at least see what HTTP triggers are causing high load through metrics, address them, and the try to downgrade back to Consumption plan.

    If you've already done that, then we'll need to work more closely with you to investigate this issue.

    EDIT 2023 May 12

    Currently, Function Apps doesn't support HTTP log capture like web apps. However, the lack of logs from the function instances and timeout/service unavailable errors received by the client sending the HTTP request has good correlation to these types of failures.

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