simple_on_shutdown

This Rust library consists of a convenient macro to specify on shutdown callbacks. This is useful for all runtimes you do not have control over. It's super simple and stripped-down.

The generated main() function of an "actix" web server is a good example. With the exported macro on_shutdown!() you can easily specify code, that should run during program termination/shutdown.

With "runtimes you do not have control over" I mean that for example actix doesn't let you specify shutdown callbacks by itself. In such cases my macro may be a better option.

IMPORTANT: Use this on the top level of your main() or whatever your current runtimes main function is! The code gets executed when the context it lives in gets dropped. This can be called multiple times (at least with stable Rust 1.48.0) without problem.

Usage

Recommended

use simple_on_shutdown::on_shutdown;
// ...
on_shutdown!(println!("shutted down"));

Not recommended, old way

// Not recommended, old way
#[macro_use]
extern crate simple_on_shutdown;
// ...
on_shutdown!(println!("shutted down"));

Simple Example

See also "example/"-dir in repository!

use simple_on_shutdown::on_shutdown;

fn main() {
    // some code ...
    
    // Important that the returned value of the macro lives through
    // the whole lifetime of main(). It gets dropped in the end.
    on_shutdown!(println!("shut down with success"));
    // some code ...
}

Actix Web Server

See also "example/"-dir in repository!

use actix_web::{get, HttpServer, App, HttpResponse, Responder};
use simple_on_shutdown::on_shutdown;

#[get("/")]
async fn get_index() -> impl Responder {
    HttpResponse::Ok().body("Hello World")
}

#[actix_web::main]
async fn main() -> std::io::Result<()> {
    // Important that the returned value of the macro lives through
    // the whole lifetime of main(). It gets dropped in the end.
    on_shutdown!({
                // the actual code
                println!("This gets executed during shutdown. Don't do expensive operations here.");
    });

    HttpServer::new(|| {
        App::new()
            .service(get_index)
    })
        .bind(format!("localhost:{}", 8080))?
        .run()
        .await
}

⚠ Restrictions ⚠

• There is no guarantee that this gets executed in "non-regular" shutdown scenarios, like CTRL+C / SIGINT / SIGTERM
• your application must handle SIGINT/SIGTERM (and other signals) in a proper way to allow a gracefully "non-regular" shutdown (Actix web framework does this for example)
  • i.e. if you don't handle signals CTRL+C will immediately shut down your app
• but even in that case: there is no guarantee in every case that the operating system gives your application more time after it has been (forcefully) killed
• this behaviour differs a little bit between Windows and UNIX. See example/src/bin/simple_example_ctrl_c_signal for more details.