REST in Practice

Chapter 6. Scaling Out

THE WEB IS THE WORLD’S LARGEST ONLINE INFORMATION SYSTEM, scaling to billions of devices and users. Hypermedia documents connect a near limitless number of resources, most of which are designed to be read, not modified. At a grand scale, structural hypermedia rules, helped by the safe, idempotent properties of the ubiquitous GET method, and to a lesser extent some of the other cacheable verbs.

From a programmatic web perspective, the infrastructure that has evolved on the Web—particularly around information retrieval—solves many integration challenges. In this chapter, we look at how we can use that infrastructure and some associated patterns to build scalable, fault-tolerant enterprise applications.

GET Back to Basics

According to the HTTP specification, GET is used to retrieve the representation of a resource. Example 6-1 shows a consumer retrieving a representation of an order resource from a Restbucks service by sending an HTTP GET request to the server where the resource is located.

Example 6-1. A GET request using a relative URI

GET /order/1234 HTTP/1.1
Connection: keep-alive
Host: restbucks.com

The value of the Host header plus the relative path that follows GET together give the complete URI of the resource being requested—in this case, http://restbucks.com/order/1234. In HTTP 1.1, servers must also support absolute URIs, in which case the Host header is not necessary, as shown in Example 6-2.

Example 6-2. A GET request using an absolute URI ...