Designing Reactive Systems

Chapter 1. Introduction

We are in the midst of a rapid evolution in how we build computer systems. Applications must be highly responsive to hold the interest of users with ever-decreasing attention spans, as well as evolve quickly to remain relevant to meet the ever-changing needs and expectations of the audience.

At the same time, the technologies available for building applications continue to evolve at a rapid pace (see Figure 1-1). It is now possible to effectively utilize clusters of cores on individual servers and clusters of servers that work together as a single application platform. Memory and disk storage costs have dropped. Network speeds have grown significantly, encouraging huge increases in online user activity. As a result, there has been explosive growth in the volume of data to be accumulated, analyzed, and put to good use.

Figure 1-1. It’s a New World

Put simply, science has evolved, and the requirements to serve the applications built nowadays cannot rely on the approaches used over the past 10–15 years. One concept that has emerged as an effective tool for building systems that can take advantage of the processing power harnessed by multicore, in-memory, clustered environments is the Actor model.

Created in 1973 by noted computer scientist Carl Hewitt, the Actor model was designed to be “unlike previous models of computation... inspired by physics, including ...