[UvicornAppHostingExtension] Uvicorn for FastAPI with Opentelemetry does not work : err message is No such option: --traces_exporter

[tae0y]

Hello~ I tried using the community extension to host a Uvicorn app with Aspire.AppHost.

However, I ran into the following issue. Does anyone know how to resolve it?
I'm still getting used to both Python and .NET, and I feel lost while trying to figure this out.

What I want to do :

• Applying opentelemetry to Uvicorn/FastAPI,
• and see structured Logs in Aspire Dashboard

Symptoms :

• In Aspire Dashboard Console prints Error

2025-02-08T15:34:51 Usage: uvicorn [OPTIONS] APP
2025-02-08T15:34:51 Try 'uvicorn --help' for help.
2025-02-08T15:34:51
2025-02-08T15:34:51 Error: No such option: --traces_exporter

• When .venv has opentelemetry-instrument
• UvicornAppHostingExtension.cs add following arguments automatically
• However, uvicorn does not support those options

private static void AddOpenTelemetryArguments(CommandLineArgsCallbackContext context)
{
    context.Args.Add("--traces_exporter");
    context.Args.Add("otlp");

    context.Args.Add("--logs_exporter");
    context.Args.Add("console,otlp");

    context.Args.Add("--metrics_exporter");
    context.Args.Add("otlp");
}

How to represent

• Environments : python 3.12, dotnet 9, mac M1

• Clone repository

git clone https://github.com/tae0y/aspire-apphost-uvicorn-issue
cd aspire-apphost-uvicorn-issue

• Set Python virtual environments

cd src/Python.FastAPI
python3.12 -m venv .venv
. .venv/bin/activate
pip install -r requirements.txt

• Run Aspire.AppHost

cd src
dotnet run --project Aspire.AppHost/Aspire.AppHost.csproj

[tae0y]

Hi~ Happy weekends~
I'm still getting lost to figure it out. could I recieve your help?
@tommasodotNET @Alirexaa @aaronpowell

[tae0y]

little updates!
adding fastapi/opentelemetry with AddPythonApp does not print errors!

var pythonApp = builder.AddPythonApp(
        name: "python",
        projectDirectory: "../Python.FastAPI",
        scriptPath: "app.py",
        scriptArgs: new[] {""}
    )
    .WithHttpEndpoint(
        targetPort:portValueInt,
        port:portValueInt+1)
    .WaitFor(rabbitMQContainer)
    .WaitFor(postgresqlContainer);

[tommasodotNET]

Hi @tae0y. I can confirm there's a bug here. As of today, when OTEL is enabled, we generate a command such as

uvicorn app:app --traces_exporter otlp --logs_exporter console,otlp --metrics_exporter otlp

while it should really be

opentelemetry-instrument --traces_exporter otlp --logs_exporter console,otlp --metrics_exporter otlp uvicorn app:app

I'll fire up a PR to solve this.

[tae0y]

thanks!!!!!!!! I'll wait for it ^^

[tommasodotNET]

FYI: #472