Azure function .net 8 isolated, 404

Question

I've got an azure function app (on the consumption plan) that has been running ok, I deployed a new version from an AZDO pipeline and now it just returns 404 on the function page (so I'm guessing it hasn't found the function).

The function class is public and has what looks to be the right annotations.

Answer 1

@Mike Hudgell - Lead Volunteer

Welcome to the Microsoft Q&A.

It sounds like you're encountering a common issue with Azure Functions in the isolated .NET 8 runtime. Here are a few things you can check to troubleshoot the 404 error:

FUNCTIONS_WORKER_RUNTIME: Ensure that the FUNCTIONS_WORKER_RUNTIME environment variable is set correctly. For .NET 8 isolated, it should be set to dotnet-isolated. If it's set to something else, like CSharp, it can cause issues.

Function Annotations: Double-check that your function class has the correct annotations and that the method signatures match what Azure Functions expects. For example, make sure you have the [FunctionName("YourFunctionName")] attribute on your function method.

Deployment Artifacts: Verify that the deployment artifacts are correct and that the function app is being deployed properly. Sometimes, issues can arise if the deployment process doesn't correctly sync the function triggers.

App Settings: Check the app settings in the Azure portal to ensure that all necessary settings are configured correctly. This includes connection strings, environment variables, and any other settings your function app relies on.

Logs and Diagnostics: Look at the logs and diagnostics in the Azure portal to see if there are any error messages or warnings that can give you more information about what's going wrong. The logs can often provide valuable insights into why the function is returning a 404 error.

If you've checked all of these and are still having issues, you might want to try redeploying the function app or even creating a new function app to see if the issue persists.

Let me know if you need more detailed steps on any of these points!

See:

• https://learn.microsoft.com/en-us/answers/questions/2105469/how-to-fix-c-azure-function-error-404
• https://learn.microsoft.com/en-us/answers/questions/1658082/net-8-dotnet-isolated-runtime-starup-errors-for-fu
• https://learn.microsoft.com/en-us/answers/questions/2142366/azure-isolated-function-net-8-all-httpclient-reque