Otel-Azure-PoC

This repository contains the reproduction of an issue identified with Azure App Service and OpenTelemetry when enabling CORS.

Issue

When running an Azure App Service with CORS enabled and an OpenTelemetry enabled .NET 8 application deployed the app will not generate traces to the App Service's Console even when the OpenTelemetry.Exporters.ConsoleExporter is added. If the CORS policy is disabled the traces will be generated as expected.

Steps to reproduce

1. Clone the repository
2. Open infra/app-service-with-cors.bicep and modify the resource names to unique values
3. Create an Azure App Service using the infra/app-service-with-cors.bicep
4. Open infra/app-service-without-cors.bicep and modify the resource names to unique values
5. Create an Azure App Service using the infra/app-service-without-cors.bicep
6. Deploy the Otel-Azure-PoC project to both App Services
7. Access the App Service without CORS enabled on /WeatherForecast and check the console logs
   1. Expected: The console log shows traces for the http.route WeatherForecast every time the endpoint is accessed
8. Access the App Service with CORS enabled on /WeatherForecast and check the console logs
   1. Expected: The console log shows no traces for the http.route WeatherForecast