Hydroconf

Effortless configuration management for Rust. Keep your apps hydrated!

Hydroconf is a configuration management library for Rust, based on config-rs and heavily inspired by Python's dynaconf.

• Inspired by the 12-factor configuration principles
• Effective separation of sensitive information (secrets)
• Layered system for multi environments (e.g. development, staging, production, etc.)
• Sane defaults, with a 1-line configuration loading
• Read from JSON, TOML, YAML, HJSON, INI files

The config-rs library is a great building block, but it does not provide a default mechanism to load configuration and merge secrets, while keeping the different environments separated. Hydroconf fills this gap.

Suppose you have the following file structure:

├── config
│   ├── .secrets.toml
│   └── settings.toml
└── your-executable

settings.toml:

[default]
pg.port = 5432
pg.host = 'localhost'

[production]
pg.host = 'db-0'

.secrets.toml:

[default]
pg.password = 'a password'

[production]
pg.password = 'a strong password'

Then, in your executable source (make sure to add serde = { version = "1.0", features = ["derive"] } to your dependencies):

use serde::Deserialize;
use hydroconf::Hydroconf;

#[derive(Debug, Deserialize)]
struct Config {
    pg: PostgresConfig,
}

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

fn main() {
    let conf: Config = match Hydroconf::default().hydrate() {
        Ok(c) => c,
        Err(e) => {
            println!("could not read configuration: {:#?}", e);
            std::process::exit(1);
        }
    };

    println!("{:#?}", conf);
}

If you compile and execute the program (making sure the executable is in the same directory where the config directory is), you will see the following:

$ ./your-executable
Config {
    pg: PostgresConfig {
        host: "localhost",
        port: 5432,
        password: "a password"
    }
}

Hydroconf will select the settings in the [default] table by default. If you set ENV_FOR_HYDRO to production, Hydroconf will overwrite them with the production ones:

$ ENV_FOR_HYDRO=production ./your-executable
Config {
    pg: PostgresConfig {
        host: "db-0",
        port: 5432,
        password: "a strong password"
    }
}

Settings can always be overridden with environment variables:

$ HYDRO_PG__PASSWORD="an even stronger password" ./your-executable
Config {
    pg: PostgresConfig {
        host: "localhost",
        port: 5432,
        password: "an even stronger password"
    }
}

The description of all Hydroconf configuration options and how the program configuration is loaded can be found in the documentation.