GraphQL for Modern Commerce

Chapter 4. GraphQL Servers

At a high level, a GraphQL server is responsible for responding to queries from clients. It’s typically fronted by an HTTP server and listens at https://api.myserver.com/graphql. Clients (whether GraphQL or otherwise) make requests to that endpoint, and the server responds.

A GraphQL server is composed of two parts: an HTTP server and a GraphQL engine, as shown in Figure 4-1.

Figure 4-1. GraphQL server

The core GraphQL engine accepts the schema definition upon instantiation, builds the type schema, and allows you to execute queries against that schema. This is a library of code implemented in many common programming languages.

The HTTP server accepts the GraphQL queries and then passes them to the core GraphQL engine. When the engine responds, the HTTP server then passes the JSON response back to the client.

Let’s discuss this in more detail.

Building a Type Schema

The GraphQL schema definition is purely some text. It’s like code that hasn’t been compiled yet. It’s pretty useless on its own sitting in a text file or as a string in memory somewhere. For the GraphQL schema to be of any use, it must be loaded into a GraphQL server upon instantiation. Here’s how you’d do it with GraphQL.js, which is Facebook’s reference implementation and the near standard:

var { graphql, buildSchema } = require('graphql');

// Construct a schema, using GraphQL schema language ...