Stop 502 Errors: Build a Reliable IIS Health Endpoint for Azure Application Gateway
A healthy IIS application doesn’t guarantee a healthy Azure Application Gateway backend. If your health probes fail—due to redirects, authentication, or timeouts—traffic stops, and users see 502 errors, even though your app is running fine.
This post reveals why most 502 errors behind Application Gateway are actually health probe failures, not application issues. You’ll learn the common pitfalls (like probing / or using authenticated endpoints), the exact design principles for a reliable health endpoint, and a step-by-step guide to configure both IIS and Application Gateway for maximum stability.
Whether you’re migrating IIS workloads to Azure or troubleshooting intermittent failures, this guide shows you how to eliminate false outages by building a dedicated, lightweight, unauthenticated health endpoint.