/rust-confu

No frills Rust app configuration via environment or args

Primary LanguageRustApache License 2.0Apache-2.0

Confu

No frills app configuration via environment or command line arguments for software written in Rust.

Why Confu? Geared towards microservices, and has minimal direct dependencies list: syn, quote, proc-macro2, proc-macro-error.

if a more user friendly command line parsing desired, there are great and proven crate alternatives. For example, Clap.

Features

  • at compile time (when a binary is produced for your app), captures
    • build type, i.e. debug or release
    • build version, if provided via environment variable [PREFIX]VERSION, otherwise is set to <unspecified>
  • Reads configuration from either
    • environment
    • command line arguments
    • defaults
  • configuration items may have an optional prefix like APP_
  • each config item can be
    • required - if not provided, will panic
    • protected - will display "xxxxxxx" instead of sensitive information
    • hidden - will not be displayed at all
  • Specificity: defaults -> environment -> arguments. Arguments being the most specific, will take precedence over the corresponding environment values, if such are also defined

Usage/Examples

A working example is provided in repository. And a quick usage summary here as well:

In Cargo.toml:

[dependencies]
confu = "*"

then, a code like this:

use confu::Confu;

#[derive(Confu)]
#[confu_prefix = "APP_"]
struct Config {
    #[default = "postgres"]
    db_user: String,

    #[protect]
    #[default = "postgres"]
    db_password: String,

    #[default = "127.0.0.1"]
    api_host: String,

    #[require]
    telemetry: String,

    #[hide]
    super_secret_stuff: String,
}

fn main() {
    let config = Config::confu();
    config.show();
}

should produce something like this, granted that APP_VERSION="0.1.0" environment variable is also set:

$ cargo run --quiet -- --app_telemetry=yes
  build: debug
version: 0.1.0

APP_DB_USER/--app_db_user=postgres  (default: "postgres")
APP_DB_PASSWORD/--app_db_password=xxxxxxx  (default: "xxxxxxx")
APP_API_HOST/--app_api_host=127.0.0.1  (default: "127.0.0.1")
APP_TELEMETRY/--app_telemetry=yes  (required)

if a required argument was omitted, a panic will occur:

$ cargo run --quiet
thread 'main' panicked at 'required argument APP_TELEMETRY/--app_telemetry was not provided.', examples\basic\src\config.rs:4:17
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

Roadmap to v0.2.0

  • Write the documentation
  • Write the tests
  • Produce a better error reporting in macros
  • Parse into numerical and bool types

License

Licensed under either of Apache License, Version 2.0 or MIT license at your option.

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in Confu by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.