NGINX Cookbook, 3rd Edition

Chapter 2. High-Performance Load Balancing

2.0 Introduction

Today’s internet user experience demands performance and uptime. To achieve this, multiple copies of the same system are run, and the load is distributed over them. As the load increases, another copy of the system can be brought online. This architecture technique is called horizontal scaling. Software-based infrastructure is increasing in popularity because of its flexibility, opening up a vast world of possibilities. Whether the use case is as small as a set of two system copies for high availability, or as large as thousands around the globe, there’s a need for a load-balancing solution that is as dynamic as the infrastructure. NGINX fills this need in a number of ways, such as HTTP, transmission control protocol (TCP), and user datagram protocol (UDP) load balancing, which we cover in this chapter.

When balancing load, it’s important that the impact to the client’s experience is entirely positive. Many modern web architectures employ stateless application tiers, storing state in shared memory or databases. However, this is not the reality for all. Session state is immensely valuable and vastly used in interactive applications. This state might be stored locally to the application server for a number of reasons; for example, in applications for which the data being worked is so large that network overhead is too expensive in performance. When state is stored locally to an application server, it is extremely important ...