4.1.4.2. Configure Azure Application Gateway
š” First Principle: Azure Application Gateway provides intelligent, Layer 7 web traffic management, enabling advanced routing, SSL termination, and application-level security that a standard Layer 4 load balancer cannot offer.
Scenario: You are managing a global web application. You need to route traffic to different backend services based on the URL path (e.g., /images to an image service, /api to an API backend). You also need to terminate SSL connections at the gateway to reduce backend server load.
What It Is: Azure Application Gateway is a web traffic load balancer that enables you to manage traffic to your web applications.
Key Features:
- Web Application Firewall (WAF): Protects against threats like SQL injection and cross-site scripting (XSS).
- SSL Offloading: Decrypts SSL/TLS traffic at the gateway, reducing backend server load.
- URL-based Routing: Directs requests to different backend pools based on URL paths.
- Multi-site Hosting: Hosts multiple web applications on a single gateway instance.
Core Components:
- Listeners: Monitor specific ports/protocols for incoming requests.
- Routing Rules: Connect listeners to backend pools.
- Backend Pools: Collections of backend servers.
- HTTP Settings: Define how the gateway communicates with backend servers.
Visual: Azure Application Gateway Components
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ā ļø Common Pitfall: Using Application Gateway for non-HTTP/S traffic. It is specifically designed for web traffic and will not work for other protocols like RDP or custom TCP/UDP applications.
Key Trade-Offs:
- Layer 7 Intelligence vs. Performance: Application Gateway's Layer 7 inspection and routing provide powerful features but introduce slightly more latency than a simple Layer 4 load balancer.
Reflection Question: How do Application Gateway listeners, routing rules, and backend pools (along with HTTP settings) collectively orchestrate web traffic, enabling intelligent Layer 7 routing and SSL termination for your web applications?