Azure Application Gateway is a Layer-7 load balancer that provides application-level routing and load balancing for web applications. It enables you to manage traffic based on HTTP(S) parameters, such as host headers or URL paths, and offers additional features like SSL termination, cookie-based session affinity, and Web Application Firewall (WAF) for added security. Here's a comprehensive overview:
Azure Application Gateway can distribute incoming traffic across multiple backend resources, such as virtual machines, Azure App Services, or container instances, based on rules you define. These rules can include parameters like host headers, URL paths, or query strings, enabling you to route requests to different backend pools based on the content of the request.
Application Gateway supports SSL termination, which means it can decrypt incoming SSL/TLS traffic, process the requests, and then forward the traffic to the backend resources over HTTP or HTTPS. This offloads the encryption and decryption tasks from the backend resources, improving their performance and simplifying certificate management.
In addition to SSL termination, Application Gateway also supports end-to-end SSL, which allows you to encrypt traffic between the gateway and backend resources. This ensures that your data remains encrypted throughout its entire path, providing an additional layer of security.
Application Gateway supports cookie-based session affinity, which helps to maintain the user's session state by directing all requests from the same user to the same backend resource. This is particularly useful for applications that require session persistence, such as e-commerce websites or web applications with personalized content.
Azure Application Gateway includes an integrated Web Application Firewall (WAF) that provides protection against common web vulnerabilities and threats. WAF is based on the OWASP (Open Web Application Security Project) Core Rule Set and can be configured to run in either detection or prevention mode. This helps you to secure your applications from common exploits like SQL injection, cross-site scripting (XSS), and other OWASP Top 10 vulnerabilities.
Application Gateway allows you to configure custom health probes to monitor the health and availability of your backend resources. These probes can check the status of specific URLs, HTTP status codes, or response times to determine the health of the resources. You can also monitor the performance and health of your Application Gateway using Azure Monitor and Log Analytics.
Azure Application Gateway supports autoscaling, which enables it to automatically scale the number of instances based on the incoming traffic and resource utilization. This helps you to maintain high availability and performance while efficiently managing costs.
Application Gateway can be integrated with other Azure services like Azure Traffic Manager, Azure Front Door, or Azure CDN to build comprehensive traffic management and application delivery solutions. Additionally, it can be deployed within a Virtual Network (VNet) and combined with Network Security Groups (NSGs) or Azure Firewall for enhanced security and network isolation.
Understanding Azure Application Gateway will help you design and manage scalable, secure, and high-performing web applications in Azure. Make sure to explore the official Azure Application Gateway documentation and related resources to learn more and apply this knowledge in your projects.