zonfig

zonfig loads JSON, YAML, and TOML config files into Serde types, then keeps a watched config handle up to date while the process is running.

Features

• JSON, YAML, and TOML support.
• Extension-based format detection, with an explicit format override when needed.
• A cloneable Config<T> handle that works well in HTTP application state.
• Hot reload hooks for successful updates and reload errors.
• A cooldown window to avoid repeated reloads during save bursts.

Load Once

use serde::Deserialize;

#[derive(Debug, Deserialize)]
struct AppConfig {
    host: String,
    port: u16,
}

fn main() -> Result<(), zonfig::Error> {
    let config: AppConfig = zonfig::load("config.toml")?;

    println!("{}:{}", config.host, config.port);
    Ok(())
}

Watch And Reload

use serde::Deserialize;

#[derive(Debug, Deserialize)]
struct AppConfig {
    host: String,
    port: u16,
}

#[tokio::main]
async fn main() -> Result<(), zonfig::Error> {
    let config = zonfig::watch::<AppConfig>("config.toml").await?;

    config.with(|current| {
        println!("current config: {}:{}", current.host, current.port);
    });

    config.on_change(|config| {
        println!("config changed: {}:{}", config.host, config.port);
    });

    config.on_error(|error| {
        eprintln!("config reload failed: {error}");
    });

    Ok(())
}

Config<T> is cheap to clone. Store it in application state and call with or get whenever a handler needs the current value.

For example:

#[derive(Clone)]
struct AppState {
    config: zonfig::Config<AppConfig>,
}

Set a reload cooldown:

let config = zonfig::watch_with_options::<AppConfig>(
    "config.toml",
    zonfig::WatchOptions::default()
        .with_cooldown(std::time::Duration::from_millis(500)),
)
.await?;

Notes

• Reads use ArcSwap, so get returns an Arc<T> snapshot without cloning the config.
• A failed reload keeps the last valid config.
• The watcher stays alive until all Config<T> handles are dropped.
• This crate intentionally focuses on local files. It does not merge multiple files, read remote config stores, or write config files back to disk.