The first thing to know is that Ring and the Ring Server are not, I repeat, are not the same thing. Whereas Ring provides a suite of libraries which abstract the underlying implementation details, the Ring Server library provides the ability to start an actual web server to serve a Ring handler.

Whenever we use lein ring server from the command line, we start the Ring Server (there are other ways, but we'll get to those later in this chapter, and in Chapter 11, Environment Configuration and Deployment). At startup, the Ring Server will execute any registered application initialization hooks, and then start an embedded Jetty server, which serves our application handler. Incoming requests are then processed by Ring, as described in the previous section, until we shut down our app. On shutdown, Ring stops the embedded Jetty server and executes any registered shutdown hooks.

We can see this in the interaction between our hipstr.handler and hipstr.repl namespaces. Let's...