Axum Config

Configuration management for Axum applications. Load configuration from TOML files with environment variable support.

Features

• Load configuration from TOML files
• Environment variable interpolation (${VAR} and ${VAR:default})
• Integration with Axum as extractor

Installation

cargo add axum-config

Usage

1. Define configuration structure

use serde::Deserialize;
use axum_config::config;

#[config(key = "database")]
#[derive(Debug, Clone, Deserialize)]
pub struct DatabaseConfig {
    pub host: String,
    pub port: u16,
    pub user: String,
}

2. Create configuration file

config/config.toml:

[database]
host = "${DB_HOST:localhost}"
port = 5432
user = "${DB_USER:admin}"

3. Use in your application

use axum::{Router, routing::get, Extension};
use axum_config::{Config, ExtractConfig};
use std::sync::Arc;

#[tokio::main]
async fn main() {
    let config = Config::new().expect("Failed to load config");

    let app = Router::new()
        .route("/", get(handler))
        .layer(Extension(Arc::new(config)));

    let listener = tokio::net::TcpListener::bind("127.0.0.1:3000")
        .await
        .unwrap();

    axum::serve(listener, app).await.unwrap();
}

// If your handlers are separated into another modules,
// it's recommended to rename `ExtractConfig` to `Config` for clarity.
// use axum_config::ExtractConfig as Config;

async fn handler(
    ExtractConfig(db_config): ExtractConfig<DatabaseConfig>,
) -> String {
    format!("DB: {}:{}", db_config.host, db_config.port)
}

Configuration priority

1. Explicit path: Config::from_path("path/to/config.toml")
2. Environment variable: CONFIG_FILE_PATH
3. Default path: config/config.toml
4. Executable directory: <exe_dir>/config/config.toml

Environment variables

Supports interpolation in TOML with default values:

[server]
host = "${HOST:0.0.0.0}"      # Uses HOST or defaults to "0.0.0.0"
port = "${PORT}"              # Requires PORT to be defined

Available methods

let config = Config::new().expect("Failed to load config");

// Get configuration
let db = config.get::<DatabaseConfig>();

// With default if missing
let db = config.get_or_default::<DatabaseConfig>();

// Panics if missing
let db = config.get_or_panic::<DatabaseConfig>();