How Load Balancing Powers Scalable Application Server Deployments

Application servers host core business logic and primarily handle user requests. They are usually designed as stateless systems, meaning the application itself does not store context information about a user’s request; consequently, any request can be processed by any server in the pool.

In practice, a group of application servers is assembled into a cluster through a load‑balancing server.

Request Response Process

1. All application server addresses are configured on the load‑balancing server. 2. A user request first reaches the load balancer, which selects an application server address using a load‑balancing algorithm. 3. The request packet is forwarded to the chosen application server, which then processes the request.

If the number of users grows and concurrent requests exceed the cluster’s capacity, additional servers can be added to the cluster and their information added to the load balancer, allowing some requests to be routed to the new servers and thus relieving pressure on the existing nodes.

There are many ways to implement a load‑balancing server, including DNS load balancing, HTTP redirect load balancing, HTTP forwarding load balancing, IP‑layer load balancing, and data‑link‑layer load balancing.

In practice, small‑to‑medium sites often use reverse‑proxy servers such as Nginx to achieve HTTP forwarding load balancing, while larger sites typically adopt LVS to perform IP‑layer or data‑link‑layer load balancing.