Rust & Rocket - Zero to Deploy

March 18, 2021

Rust along with Go has been growing as popular alternatives to many of the use cases of languages like C & C++. With more straightforward and centralized package management systems along with Syntax and Standard libraries that minimize many of the pain points of working with C/C++. Go/Rust offers the ability to have a lower-level language that creates faster applications but still maintains a pleasant and productive developer experience.

In a prior tutorial, I went over Go’s equivalent to Ruby on Rails, Buffalo. In this tutorial I’ll go over Rust’s big web framework, Rocket. We will build an API using a Postgres database and deploy it.

Setup

Prerequisites

Rust Nightly (a version of Rust with latest and even experimental features, released every night), if you installed rust with rustup then you can switch to nightly with the command rustup default nightly
Postgres 12 or above
generate a new cargo project cargo new personapi --bin (cargo is the package manager of the rust world, like NPM is for node)
In the cargo.toml (plays the role package.json does for node), add rocket as a dependency.

[dependencies]
rocket = "0.4.7"

Open up src/main.rs and add the following

#![feature(proc_macro_hygiene, decl_macro)]

// IMPORT ROCKET LIBRARY
#[macro_use] extern crate rocket;

// Macro for annotating our route methods
#[get("/")]
fn index() -> &'static str {
    "Hello, world!"
}

// our main function, the entry to our application starting the server, loading routes
fn main() {
    rocket::ignite().mount("/", routes![index]).launch();
}

Let’s test it our with the command cargo run and checkout localhost:8000

Routing

Let’s add another route that uses a param

#![feature(proc_macro_hygiene, decl_macro)]

// IMPORT ROCKET LIBRARY
#[macro_use] extern crate rocket;

// Macro for annotating our route methods
#[get("/")]
fn index() -> &'static str {
    "Hello, world!"
}

// Macro for annotating our route methods
#[get("/cheese/<cheeseType>")]
fn cheese(cheeseType: String) -> String {
    format!("So... you like {} cheese!", cheeseType)
}

// our main function, the entry to our application starting the server, loading routes
fn main() {
    rocket::ignite().mount("/", routes![index, cheese]).launch();
}

restart the server and go to localhost:8000/cheese/munster

Now for one that uses a URL query

// Macro for annotating our route methods
#[get("/cheese?<cheeseType>")]
fn queso(cheeseType: String) -> String {
    format!("So... you still like {} cheese!", cheeseType)
}

restart the server and go to http://localhost:8000/cheese?cheeseType=gouda

Setting up a routes file

create a new file called routes.rs and copy our existing route functions into it.

#![feature(proc_macro_hygiene, decl_macro)]

// IMPORT ROCKET LIBRARY

// Macro for annotating our route methods
#[get("/")]
pub fn index() -> &'static str {
    "Hello, world!"
}

// Macro for annotating our route methods
#[get("/cheese/<cheeseType>")]
pub fn cheese(cheeseType: String) -> String {
    format!("So... you like {} cheese!", cheeseType)
}

// Macro for annotating our route methods
#[get("/cheese?<cheeseType>")]
pub fn queso(cheeseType: String) -> String {
    format!("So... you still like {} cheese!", cheeseType)
}

update the main.rs so it’s pulling in routes from this file.

#![feature(proc_macro_hygiene, decl_macro)]

// IMPORT ROCKET LIBRARY
#[macro_use] extern crate rocket;

pub mod routes;

// our main function, the entry to our application starting the server, loading routes
fn main() {
    rocket::ignite().mount("/", routes![routes::index, routes::cheese, routes::queso]).launch();
}

Sending JSON Data

Let’s test out sending JSON Data. We have to type our JSON data as a serializable type (in this case a hashmap).

src/routes.rs

#![feature(proc_macro_hygiene, decl_macro)]
use rocket_contrib::json::Json;
use std::collections::HashMap;

// IMPORT ROCKET LIBRARY

// Macro for annotating our route methods
#[get("/")]
pub fn index() -> Json<HashMap<String, String>> {
    let mut my_map = HashMap::new();
    my_map.insert(String::from("cheese"), String::from("gouda"));
    my_map.insert(String::from("bread"), String::from("rye"));
    // turn hashmap into json and return it
    return Json(my_map);
}

Now run your server and go to localhost:8000 to see the JSON response!

Connecting a Database

Update your Cargo.toml with the following libraries

[dependencies]
rocket = "0.4.7"
dotenv = "0.15.0"
serde = "1.0.124"
serde_json = "1.0.64"
serde_derive = "1.0.124"
postgres = "0.19.0"

[dependencies.rocket_contrib]
version = "0.4.7"
default-features = false
features = ["json", "serve"]

Create a Postgres table called rocketpeople createdb rocketpeople
Hop on PSQL and create a table psql rocketpeople then CREATE TABLE people (id SERIAL, name VARCHAR(100), age INTEGER);
Add some seed data INSERT INTO people (name, age) VALUES ('Alex', 35), ('Bob', 50);;
create a .env file with the following:

DATABASE_STRING="user=test5 password=test5 dbname=rocketpeople sslmode=disable host=localhost port=5432"

Create a personroutes.rs with the following code to setup database connection and CRUD routes.

use rocket_contrib::json::Json;
use std::collections::HashMap;
use serde::{Serialize, Deserialize};
use postgres::{Client, NoTls, Error};
use dotenv::dotenv;
use std::env;

// CREATE STRUCT THAT IS SERIALIZABLE INTO JSON
#[derive(Serialize, Deserialize, Debug)]
pub struct Person {
    id: i32,
    name: String,
    age: i32
}

// CREATE FUNCTION TO ESABLISH DATABASE CONNECTION
fn getConn() -> Result<Client, Error> {
    // GET DATABASE URL ENV VARIABLE
    let uri;
    dotenv().ok();
    match env::var("DATABASE_STRING") {
        Ok(val) => uri = val,
        Err(_e) => uri = "none".to_string(),
    }
    print!("{}", uri);
    // return database connection
    return Client::connect(&uri, NoTls);
}

// INDEX ROUTE TO GET ALL PEOPLE
#[get("/")]
pub fn index() -> Json<Vec<Person>> {
    //declare vector to hold people
    let mut result: Vec<Person> = Vec::new();

    //query database and build vector
    match getConn(){
        Ok(val) => {
            let mut client = val;
            for row in client.query("SELECT * FROM people;", &[]).unwrap() {
                let id:i32 = row.get(0);
                let name: String= row.get(1);
                let age: i32 = row.get(2);
                result.push(Person { id, name, age});
            }
        },
        Err(err) => print!("{}", err),
    }
    
    // turn hashmap into json and return it
    return Json(result);
}

// CREATE ROUTE TO CREATE A NEW PERSON
#[post("/<name>/<age>",)]
pub fn create(name: String, age: i32) -> String {

    //insert new person into database
    match getConn(){
        Ok(val) => {
            let mut client = val;
            client.execute("INSERT INTO people (name, age) VALUES ($1, $2)",
            &[&name, &age]).ok();
        },
        Err(err) => print!("{}", err),
    }
    
    // return string denoting completion
    return String::from("Request Complete");
}

// UPDATE ROUTE TO UPDATE A PERSON
#[put("/<id>/<name>/<age>",)]
pub fn update(id: i32, name: String, age: i32) -> String {

    //insert new person into database
    match getConn(){
        Ok(val) => {
            let mut client = val;
            client.execute("UPDATE people SET name=$1, age=$2 WHERE id=$3;",
            &[&name, &age, &id]).ok();
        },
        Err(err) => print!("{}", err),
    }
    
    // return string denoting completion
    return String::from("Request Complete");
}

// DELETE ROUTE TO DELETE PEOPLE
#[delete("/<id>",)]
pub fn destroy(id: i32) -> String {

    //insert new person into database
    match getConn(){
        Ok(val) => {
            let mut client = val;
            client.execute("DELETE FROM people WHERE id=$1",
            &[&id]).ok();
        },
        Err(err) => print!("{}", err),
    }
    
    // return string denoting completion
    return String::from("Request Complete");
}

Notice we did use the request body to create and update database entries. This was cause to do so in Rocket you have to implement a custom FromData trait on your Struct which was a little more complicated than necessary for this tutorial so I opted for using URL params instead.

Now, let’s pull in some our recently added libraries and mount are new routes in our main.rs.

#![feature(proc_macro_hygiene, decl_macro)]

// IMPORT ROCKET LIBRARY
#[macro_use] extern crate dotenv;
#[macro_use] extern crate rocket;
#[macro_use] extern crate serde;
#[macro_use] extern crate serde_derive;
#[macro_use] extern crate serde_json;
#[macro_use] extern crate postgres;

pub mod routes;
pub mod personroutes;
use dotenv::dotenv;
use std::env;


// our main function, the entry to our application starting the server, loading routes
fn main() {


    let uri = env::var("DATABASE_URL");
    print!("{:?}", uri.ok());

    rocket::ignite()
    .mount("/", routes![routes::index, routes::cheese, routes::queso])
    .mount("/people", routes![personroutes::index, personroutes::create, personroutes::update])
    .launch();
}

Deployment

create a file called rust-toolchain with the following

nightly

create a file called Procfile with the following

web: ROCKET_PORT=$PORT ./target/release/personapi

create a new Heroku project heroku create projectName
specify the buildpack heroku buildpacks:set emk/rust

This will work… to configure your heroku postgres:

create a new heroku postgres
use the terminal command within the database credentials (in the database settings) to get to the psql command line, add the table and some seed data.
create a new config var DATABASE_STRING

"user=test5 password=test5 dbname=rocketpeople sslmode=require host=localhost port=5432"

Heroku TLS Handshake

So here everything should be working except the database still. This is cause Heroku Postgres needs particular handling of SSL and TLS. It took me a while to figure this out but by looking at the source code of this library I was able to do so.

So in our Cargo.toml we need to bring in two more libraries…

openssl = "0.10.33"
postgres-openssl = "0.5.0"

then in personroutes.rs we import the following.

use openssl::ssl::{SslConnector, SslMethod, SslVerifyMode};
use postgres_openssl::MakeTlsConnector;

create this function to return a new TLS connector

//CREATE HEROKU TLS BUILDER
fn get_connector() -> MakeTlsConnector {
    // Create Ssl postgres connector without verification as required to connect to Heroku.
    let mut builder = SslConnector::builder(SslMethod::tls()).unwrap();
    builder.set_verify(SslVerifyMode::NONE);
    MakeTlsConnector::new(builder.build())
}

Then update our connection code to use the new connect

// CREATE FUNCTION TO ESABLISH DATABASE CONNECTION
fn getConn() -> Result<Client, Error> {
    // GET DATABASE URL ENV VARIABLE
    let uri;
    let connector = get_connector();
    dotenv().ok();
    match env::var("DATABASE_URL2") {
        Ok(val) => uri = val,
        Err(_e) => uri = "none".to_string(),
    }
    print!("{}", uri);
    // return database connection
    return Client::connect(&uri, connector);
}

push up the new code and should be working

Using the Request Body

Figured out the trick to this. Instead of having to create an implementation for each of your structs of the FromData trait. If you use the JSON struct built into Rocket, this has the FromData trait so you can wrap the type of your data in it.

After receiving the data, the into_inner function allows you to unpack the JSON, and JSON function allows you to encode back into JSON. Here are two additional routes to see this at work.

// Receiving a Hash Map as the body
#[post("/bread", data = "<body>")]
pub fn rye(body:Json<HashMap<String, String>>) -> Json<HashMap<String, String>> {
    return body;
}

// CREATE STRUCT THAT IS SERIALIZABLE INTO JSON
#[derive(Serialize, Deserialize, Debug)]
pub struct Cheese {
    name: String,
    age: i32
}

// Receiving a Struct as body
#[post("/bread2", data = "<body>")]
pub fn wheat(body:Json<Cheese>) -> Json<Cheese> {
    // unpack the json
    let cheese = body.into_inner();
    // print the cheese struct
    print!("{:?}", cheese);
    // encode the cheese struct as json and send out
    return Json(cheese);
}

Handling Cors in Rocket

add the following to your Cargo.toml

rocket_cors = "0.5.2"

then add this to your main.rs

//import the crate
extern crate rocket_cors;

//create a cors struct and attach it as a fairing
fn main() {

    // Create CORS STRUCT
    let corsOptions = rocket_cors::CorsOptions::default();
    print!("{:?}", corsOptions);
    let mut CORS = corsOptions.to_cors().expect("this didn't work");
    
    // igniting the rocket app
    rocket::ignite()
    .attach(CORS)

This default to very open settings, if you want to customize it further read the documentation for rocket_cors.