rust

Rust Backend Patterns

Overview

Rust patterns for building backend services with Axum.

Project Structure

project/
├── src/
│   ├── main.rs               # Entry point
│   ├── lib.rs                # Library root
│   ├── config.rs             # Configuration
│   ├── error.rs              # Error types
│   ├── routes/               # Route handlers
│   │   ├── mod.rs
│   │   └── users.rs
│   ├── services/             # Business logic
│   ├── repositories/         # Data access
│   ├── models/               # Domain models
│   └── middleware/           # HTTP middleware
├── migrations/               # SQLx migrations
├── tests/                    # Integration tests
├── Cargo.toml
└── .env

Axum Application

Main Application

// src/main.rs
use axum::{
    routing::{get, post},
    Router,
};
use sqlx::postgres::PgPoolOptions;
use std::sync::Arc;
use tower_http::cors::CorsLayer;

mod config;
mod error;
mod routes;
mod services;
mod repositories;

use config::Config;

#[derive(Clone)]
pub struct AppState {
    pub db: sqlx::PgPool,
    pub config: Arc<Config>,
}

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    dotenvy::dotenv().ok();
    tracing_subscriber::init();

    let config = Config::from_env()?;

    let pool = PgPoolOptions::new()
        .max_connections(config.database.max_connections)
        .connect(&config.database.url)
        .await?;

    sqlx::migrate!().run(&pool).await?;

    let state = AppState {
        db: pool,
        config: Arc::new(config),
    };

    let app = Router::new()
        .route("/health", get(|| async { "ok" }))
        .nest("/api/users", routes::users::router())
        .with_state(state)
        .layer(CorsLayer::permissive());

    let listener = tokio::net::TcpListener::bind("0.0.0.0:3000").await?;
    tracing::info!("listening on {}", listener.local_addr()?);
    axum::serve(listener, app).await?;

    Ok(())
}

Configuration

// src/config.rs
use serde::Deserialize;

#[derive(Debug, Deserialize)]
pub struct Config {
    pub database: DatabaseConfig,
    pub jwt: JwtConfig,
}

#[derive(Debug, Deserialize)]
pub struct DatabaseConfig {
    pub url: String,
    #[serde(default = "default_max_connections")]
    pub max_connections: u32,
}

#[derive(Debug, Deserialize)]
pub struct JwtConfig {
    pub secret: String,
    #[serde(default = "default_expiry")]
    pub expiry_hours: u64,
}

fn default_max_connections() -> u32 { 10 }
fn default_expiry() -> u64 { 24 }

impl Config {
    pub fn from_env() -> Result<Self, config::ConfigError> {
        config::Config::builder()
            .add_source(config::Environment::default().separator("__"))
            .build()?
            .try_deserialize()
    }
}