Understanding Azure Function Observability with OpenTelemetry DotNet Edition

New Relic observes a growing trend of customers adopting OpenTelemetry for observability, especially in serverless environments like Azure Functions. This guide provides a detailed walkthrough on how to instrument DotNet Azure Functions with OpenTelemetry, offering end-to-end visibility in New Relic. It explains the architecture of Azure Functions, comprising the Azure Functions Host and the .NET Isolated Worker process, and how to enable OpenTelemetry in these components. The guide emphasizes the importance of setting the "telemetryMode" in the host.json file to "OpenTelemetry" to ensure comprehensive telemetry data collection. It also discusses the prerequisites for configuring OpenTelemetry in the application, including necessary packages and configurations for HTTP client instrumentation. The text highlights the automatic collection of metrics for outgoing HTTP requests and the benefits of integrating with New Relic's APM UI for enhanced monitoring. Additionally, it covers the configuration of data exporters and sampling settings, guiding users through the process of achieving a complete trace experience by combining configurations in both Program.cs and host.json files.