Rocket Core Knowledge

Full Reference: See advanced.md for custom guards (authentication, API key), fairings (CORS, timing), database state, error catchers, and testing patterns.

Deep Knowledge: Use mcp__documentation__fetch_docs with technology: rocket for comprehensive documentation.

Basic Setup

# Cargo.toml
[dependencies]
rocket = { version = "0.5", features = ["json"] }
serde = { version = "1", features = ["derive"] }
serde_json = "1"
tokio = { version = "1", features = ["full"] }

#[macro_use] extern crate rocket;

#[get("/")]
fn index() -> &'static str {
    "Hello, World!"
}

#[launch]
fn rocket() -> _ {
    rocket::build().mount("/", routes![index])
}

Routing

#[get("/users/<id>")]
fn get_user(id: u32) -> String {
    format!("User {}", id)
}

#[post("/users", data = "<user>")]
fn create_user(user: Json<CreateUser>) -> Json<User> {
    Json(User::from(user.into_inner()))
}

#[get("/files/<path..>")]
fn get_file(path: PathBuf) -> Option<NamedFile> {
    NamedFile::open(Path::new("static/").join(path)).ok()
}

// Query parameters
#[derive(FromForm)]
struct Pagination { page: Option<u32>, per_page: Option<u32> }

#[get("/users?<pagination..>")]
fn list_users(pagination: Pagination) -> Json<Vec<User>> {
    let page = pagination.page.unwrap_or(1);
    Json(fetch_users(page, pagination.per_page.unwrap_or(20)))
}

// Mounting
#[launch]
fn rocket() -> _ {
    rocket::build()
        .mount("/", routes![index])
        .mount("/api/v1", routes![list_users, get_user, create_user])
}

Request Guards

// JSON body
#[post("/users", data = "<user>")]
fn create_user(user: Json<CreateUser>) -> Json<User> {
    Json(User::from(user.into_inner()))
}

// Form data
#[post("/login", data = "<login>")]
fn login(login: Form<LoginForm>) -> String {
    format!("Welcome, {}", login.username)
}

// Cookies
#[get("/session")]
fn session(cookies: &CookieJar<'_>) -> Option<String> {
    cookies.get("session_id").map(|c| c.value().to_string())
}

State Management

use std::sync::atomic::{AtomicU64, Ordering};

struct HitCount(AtomicU64);

#[get("/count")]
fn count(hit_count: &State<HitCount>) -> String {
    let count = hit_count.0.fetch_add(1, Ordering::Relaxed);
    format!("Hits: {}", count)
}

#[launch]
fn rocket() -> _ {
    rocket::build()
        .manage(HitCount(AtomicU64::new(0)))
        .mount("/", routes![count])
}

Fairings (Middleware)

use rocket::fairing::AdHoc;

#[launch]
fn rocket() -> _ {
    rocket::build()
        .attach(AdHoc::on_liftoff("Liftoff", |_| Box::pin(async {
            println!("Rocket has launched!");
        })))
}

When NOT to Use This Skill

Axum projects - Axum integrates better with Tower ecosystem
Actix-web projects - Actix has more performance optimizations
Stable Rust requirement - Rocket requires nightly (though v0.5 works on stable)

Anti-Patterns

Anti-Pattern	Why It's Bad	Solution
Using `Outcome::Forward` everywhere	Routes become hard to trace	Use specific error types
Not using request guards	Repetitive validation code	Create custom `FromRequest` guards
Mutable state without sync primitives	Data races	Use `Mutex` or `RwLock` with `State`
No database connection pooling	Resource exhaustion	Use `rocket_db_pools`
Hardcoded secrets in Rocket.toml	Security risk	Use environment variables

Quick Troubleshooting

Problem	Diagnosis	Fix
"Use of unstable library feature"	Wrong Rust version	Install nightly or use Rocket 0.5+
Route not matching	Rank conflict	Specify `rank` attribute or reorder routes
Guard returns error	Validation failed	Check guard implementation logic
Database error on startup	Wrong connection string	Verify `Rocket.toml` database config
CORS issues	No fairing	Add CORS fairing with proper config

Production Checklist

Rocket.toml configured for production
CORS fairing attached
Custom error catchers registered
Request guards for authentication
Database pool configured
Health/readiness endpoints
Secret key set for release

rocket

Rocket Core Knowledge

Basic Setup

Routing

Request Guards

State Management

Fairings (Middleware)

When NOT to Use This Skill

Anti-Patterns

Quick Troubleshooting

Production Checklist

Reference Documentation