Fiddler with dotnet-isolated Az Function - Error starting gRPC call

Question

I have a C# dotnet 5 Azure Function in VS2019 configured with "FUNCTIONS_WORKER_RUNTIME": "dotnet-isolated".

If I run the function in the dev environment (ctrl + F5) while Fiddler is running then I get the following error:

Grpc.Core.RpcException: Status(StatusCode="Internal", Detail="Error starting gRPC call. HttpRequestException: Requesting HTTP version 2.0 with version policy RequestVersionOrHigher while HTTP/2 is not enabled.

The function will run fine if Fiddler is not running.

Anyone know how to resolve this?

Microcrystalline

As suggested in the below reference SO thread #66500695 The workaround for local development is to manually set the default proxy for the HttpClient before making the gRPC call – Honestly

Answer 1

I've made Fiddler work with an Azure Function project with two additions to the standard setup:

1. Add 127.0.0.1 to the bypass list
2. Add tls1.1 and tls1.2 to the supported protocols and skip decryption for 127.0.0.1

Dekeles

This didn't work for me. protocols already were the same as in your screenshot, I'm using fiddler v5.0.20243.10853 and .net8 dotnet-isolated – Fulton

Answer 2

I recommend to install Fiddler Everywhere which has HTTP/2 and gRPC support.

To setup Fiddler Everywhere make sure

1. 'Ignore server certificate errors' is checked (Settings -> HTTPS)
2. Enabled HTTP/2 support (Settings -> Connections)
3. Bypass Fiddler for URLs that start with 127.0.0.1 (Settings -> Connections)

https://www.telerik.com/blogs/introduction-grpc-fiddler-everywhere

Fenestella

You seem to have misunderstood StackOverflow concepts a little, maybe because you never took the highly recommended tour. – Chequer