Unlock the Power of GraphQL in Rust
As the Rust ecosystem continues to evolve, it’s becoming an increasingly attractive option for building robust and efficient backend web services. In this comprehensive guide, we’ll explore how to harness the power of GraphQL in Rust using the Juniper library, and demonstrate how to build a scalable and performant web application that interacts with a Postgres database.
Getting Started with Juniper and GraphQL
To begin, create a new Rust project using Cargo and add the necessary dependencies to your Cargo.toml file, including Juniper for GraphQL functionality, Warp for the web server, and Tokio-Postgres for database access. Since we’ll be working with async Rust, we’ll also need an executor to poll Futures; in this example, we’ll utilize the Tokio executor with the macros feature flag for an async main function.
Setting Up the Web Server
Before diving into GraphQL, let’s establish a web server to handle HTTP requests. Juniper’s flexibility allows it to work seamlessly with any web server, so feel free to adapt this example to suit your needs. We’ll define two routes: one for handling GraphQL requests and another for serving the GraphiQL test client.
Defining the Schema and Context
Next, we’ll define the Schema, QueryRoot, MutationRoot, and Context types. We’ll create a schema and convert it into a Warp filter, making it accessible in our route handlers. We’ll also define a context that can contain elements like database connections.
Implementing GraphQL Resolvers
With our server boilerplate and database in place, we can now focus on implementing GraphQL resolvers to bring our application to life. Let’s create a struct for customer data, leveraging the derive macro to make our custom data type work seamlessly with Juniper.
GraphQL Mutations
We’ll start by implementing GraphQL mutations to add customer data. The MutationRoot struct is where all GraphQL mutations are defined. We’ll create a simple register_customer method that returns a user with an ID, name, age, email, and address. This method will be wrapped in Ok() since it returns a Result.
Storing Data in the Database
Instead of simply returning the data, we can store it in our database. We’ll generate a random UUID, save the user in the database, and normalize the provided email by converting it to lowercase. We’ll also explore how to update a customer’s email and delete a customer record.
GraphQL Queries
Queries are implemented similarly to mutations, but using QueryRoot instead of MutationRoot. Our first query will find a customer with a given ID, using the query_one method to return exactly one database row or an error. We’ll also explore how to query a list of customers, using the query method to return multiple rows from the database.
Taking Your GraphQL Application to the Next Level
Now that you’ve gained a solid understanding of how GraphQL works in Rust with Juniper, you can take your application to the next level by adding authentication and permissions, using custom error types, and exploring the possibilities of nested custom data types. With Rust’s powerful macro support, working with GraphQL is a breeze.