What is Azure Application Gateway?

Azure Application Gateway is a web traffic load balancer that enables traffic management to web applications. It is a part of Microsoft Azure's cloud computing service suite, designed to ensure that web applications can scale up or down based on demand and remain highly available. The Application Gateway offers various features, including URL-based routing, cookie-based session affinity, secure sockets layer (SSL) termination, Web Application Firewall (WAF), and the capability to host multiple sites behind a single application gateway instance.

How does Azure Application Gateway work?

Azure Application Gateway directs incoming web traffic to specific resources in a backend pool. These resources include Azure Virtual Machines, Azure Virtual Machine Scale Sets, or Azure App Services. The routing decisions are based on several factors, such as the URL path, host headers, and session affinity. The Application Gateway supports SSL/TLS termination, which means it can decrypt incoming SSL/TLS sessions and analyze the traffic before routing it to the backend servers. This offloads the SSL/TLS decryption tasks from the web servers and helps in better resource utilization and scalability. It also provides a Web Application Firewall (WAF) that protects web applications from common web-based attacks like SQL injection, cross-site scripting, and session hijacking.

Use Cases

Azure Application Gateway is used in various scenarios where managing, securing, and optimizing web traffic is essential. Organizations with heavy web traffic use it to distribute loads across multiple servers, ensuring no single server becomes a bottleneck. E-commerce sites leverage their ability to maintain session affinity, which is crucial for keeping a user's session active and directed to the same server for the duration of their visit. Companies that require enhanced security measures utilize the WAF capabilities to protect their applications from web vulnerabilities. Moreover, businesses hosting multiple websites find Azure Application Gateway's capacity to manage multiple sites through a single gateway highly beneficial for simplifying infrastructure and reducing costs.