Azure Function App timing out at an interval of what functionTimeout parameter is equal to

Question

The functionTimeout parameter in my host.json file is set to "functionTimeout": "00:45:00"

I'm seeing timeouts happen every 45 minute interval.

When I dig into the timeouts through Application Insights, they have not been running for 45 minutes. Here's an example:

Start:

End:

I have also done what I can to make sure my function isn't running in parallel. I've limited the function to run on 1 machine and one instance using "batchSize": 1 in my host.json file.

How is it possible that I'm seeing timeouts before the maximum allotted time for the function to run before a timeout? And how come I'm seeing timeouts happen every 45 minute interval, which aligns with what my functionTimeout parameter is set to?

host.json details:

{
  "version": "2.0",
  "logging": {
    "applicationInsights": {
      "samplingSettings": {
        "isEnabled": true,
        "excludedTypes": "Request"
      }
    }
  },
  "extensionBundle": {
    "id": "Microsoft.Azure.Functions.ExtensionBundle",
    "version": "[2.*, 3.0.0)"
  },
  "extensions": {
    "queues": {
      "batchSize": 1
    }
  },
  "functionTimeout": "00:45:00"
}

Answer 1

There is a limit to the maximum amount of timeout which can be allotted in a function.

This limit is determined by the you subscription plan and it varies accordingly.

for e.g., the maximum timeout in consumption plan is 10 min.

Please check your subscription plan and edit accordingly.

Refer the following article by Chris Peitschmann for Indepth explanation on azure function timeouts.