OTEL signals missing in Dashboard from ASP.NET Core application hosted in container

[Kralizek]

Maybe related to #4131

I have a ASP.NET Core web application packaged as a container that I add to other application AppHosts.

I am trying to get OTEL signals (traces mostly) to appear in the Aspire dashboard but nothing is showing up and I have no idea what I am missing.

public static IHostApplicationBuilder ConfigureOpenTelemetry(this IHostApplicationBuilder builder)
{
    builder.Logging.AddOpenTelemetry(logging =>
    {
        logging.IncludeScopes = true;
        logging.IncludeFormattedMessage = true;
    });
    
    var otel = builder.Services.AddOpenTelemetry()
        .ConfigureResource(r => r.AddService(builder.Environment.ApplicationName));

    otel.WithMetrics(m => m
        .AddHttpClientInstrumentation()
        .AddAspNetCoreInstrumentation()
        .AddRuntimeInstrumentation()
        .AddMeter(Telemetry.ServiceName));

    otel.WithTracing(t => t
        .AddSource(IdentityServerConstants.Tracing.Basic)
        .AddAspNetCoreInstrumentation()
        .AddHttpClientInstrumentation());

    builder.AddOpenTelemetryExporters();

    return builder;
}

private static IHostApplicationBuilder AddOpenTelemetryExporters(this IHostApplicationBuilder builder)
{
    var useOtlpExporter = !string.IsNullOrWhiteSpace(builder.Configuration["OTEL_EXPORTER_OTLP_ENDPOINT"]);

    if (useOtlpExporter)
    {
        builder.Services.AddOpenTelemetry().UseOtlpExporter();
    }

    return builder;
}

The dashboard shows that the container is getting all the OTEL environment variables injected but stuff is still not showing up in the traces, logs and metrics pages.

I tried to enable ASPIRE_ALLOW_UNSECURED_TRANSPORT in the launch profile of the AppHost, but I'm not sure if that makes the trick, especially because we purged the http entry

{
  "$schema": "https://json.schemastore.org/launchsettings.json",
  "profiles": {
    "https": {
      "commandName": "Project",
      "dotnetRunMessages": true,
      "launchBrowser": true,
      "applicationUrl": "https://localhost:17068",
      "environmentVariables": {
        "ASPNETCORE_ENVIRONMENT": "Development",
        "DOTNET_ENVIRONMENT": "Development",
        "DOTNET_DASHBOARD_OTLP_ENDPOINT_URL": "https://localhost:21251",
        "DOTNET_RESOURCE_SERVICE_ENDPOINT_URL": "https://localhost:22041"
      }
    }
  }
}