Azure function app timeout for app service plan

Question

I did follow the guidelines mentioned in https://docs.microsoft.com/da-dk/azure/azure-functions/functions-host-json#functiontimeout to increase the default timeout of function app host on app service plan from 30 mins to 2h by updating the host file with "functionTimeout": "02:00:00"

On checking function app's event viewer logs, I could see timeout limit is still 30m. Adding the error message for reference,

        <EventData>
            <Data>Application: w3wp.exe
CoreCLR Version: 4.6.27317.7
Description: The process was terminated due to an unhandled exception.
Exception Info: Microsoft.Azure.WebJobs.Host.FunctionTimeoutException: Timeout value of 00:30:00 was exceeded by function: CreateRequestApplicationPostProcessor
   at Microsoft.Azure.WebJobs.Host.Executors.FunctionExecutor.TryHandleTimeoutAsync(Task invokeTask, CancellationToken shutdownToken, Boolean throwOnTimeout, CancellationToken timeoutToken, TimeSpan timeoutInterval, IFunctionInstance instance, Action onTimeout) in C:\projects\azure-webjobs-sdk-rqm4t\src\Microsoft.Azure.WebJobs.Host\Executors\FunctionExecutor.cs:line 631
   at Microsoft.Azure.WebJobs.Host.Executors.FunctionExecutor.InvokeAsync(IFunctionInvoker invoker, ParameterHelper parameterHelper, CancellationTokenSource timeoutTokenSource, CancellationTokenSource functionCancellationTokenSource, Boolean throwOnTimeout, TimeSpan timerInterval, IFunctionInstance instance) in C:\projects\azure-webjobs-sdk-rqm4t\src\Microsoft.Azure.WebJobs.Host\Executors\FunctionExecutor.cs:line 547
   at Microsoft.Azure.WebJobs.Host.Executors.FunctionExecutor.ExecuteWithWatchersAsync(IFunctionInstance instance, ParameterHelper parameterHelper, ILogger logger, CancellationTokenSource functionCancellationTokenSource) in C:\projects\azure-webjobs-sdk-rqm4t\src\Microsoft.Azure.WebJobs.Host\Executors\FunctionExecutor.cs:line 503
   at Microsoft.Azure.WebJobs.Host.Executors.FunctionExecutor.ExecuteWithLoggingAsync(IFunctionInstance instance, ParameterHelper parameterHelper, IFunctionOutputDefinition outputDefinition, ILogger logger, CancellationTokenSource functionCancellationTokenSource) in C:\projects\azure-webjobs-sdk-rqm4t\src\Microsoft.Azure.WebJobs.Host\Executors\FunctionExecutor.cs:line 439
   at Microsoft.Azure.WebJobs.Host.Executors.FunctionExecutor.ExecuteWithLoggingAsync(IFunctionInstance instance, FunctionStartedMessage message, FunctionInstanceLogEntry instanceLogEntry, ParameterHelper parameterHelper, ILogger logger, CancellationToken cancellationToken) in C:\projects\azure-webjobs-sdk-rqm4t\src\Microsoft.Azure.WebJobs.Host\Executors\FunctionExecutor.cs:line 249
   at Microsoft.Azure.WebJobs.Host.Executors.FunctionExecutor.ExecuteWithLoggingAsync(IFunctionInstance instance, FunctionStartedMessage message, FunctionInstanceLogEntry instanceLogEntry, ParameterHelper parameterHelper, ILogger logger, CancellationToken cancellationToken) in C:\projects\azure-webjobs-sdk-rqm4t\src\Microsoft.Azure.WebJobs.Host\Executors\FunctionExecutor.cs:line 293
   at Microsoft.Azure.WebJobs.Host.Executors.FunctionExecutor.TryExecuteAsync(IFunctionInstance functionInstance, CancellationToken cancellationToken) in C:\projects\azure-webjobs-sdk-rqm4t\src\Microsoft.Azure.WebJobs.Host\Executors\FunctionExecutor.cs:line 89
   at Microsoft.Azure.WebJobs.Host.Timers.WebJobsExceptionHandler.&lt;&gt;c__DisplayClass3_0.&lt;OnUnhandledExceptionAsync&gt;b__0() in C:\projects\azure-webjobs-sdk-rqm4t\src\Microsoft.Azure.WebJobs.Host\Timers\WebJobsExceptionHandler.cs:line 54
   at System.Threading.Thread.ThreadMain_ThreadStart()
   at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state)
--- End of stack trace from previous location where exception was thrown ---
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Threading.ThreadHelper.ThreadStart()
</Data>
        </EventData>
    </Event>

Appreciate your help in overriding a custom timeout value.

Answer 1

If you run on an App Service plan, you should enable the Always on setting so that your function app runs correctly.

Even with Always On enabled, the execution timeout for individual functions is controlled by the functionTimeout setting in the host.json project file.

For more details you could refer to this article.

Answer 2

you can always use the attribute [Timeout("1:00:00")] on function level to override the default timeout