Macro simple_on_shutdown::on_shutdown

macro_rules! on_shutdown {
    ($cb:block) => { ... };
    ($cb:expr) => { ... };
}

This crate consists of a convenient macro to specify on shutdown callbacks called on_shutdown. It takes code that should be executed when your program exits (gracefully).

Internally it creates a closure that gets executed when the context gets dropped, i.e. when main() exits. There is also on_shutdown_move available in case the closure needs to capture vars, like an Arc<>.

In theory this macro can be used everywhere where the context gets dropped. But it has a nice expressive name so that one exactly knows what it should achieve in code. A good example is the main() function in an actix-web-Server. For example you want to log to a file when the server was shut down.

There is no guarantee that this gets executed during "non-regular" shutdown scenarios, like when receiving CTRL+C / SIGINT / SIGTERM. This depends on whether your application properly handles signals and if the operating system gives your application time before it gets totally killed/stopped..

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 macro can be called multiple times (at least with stable Rust 1.48.0) without problems.

This crate uses the log crate on the debug level.

Also see on_shutdown_move.

Example

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"));

    // can be used multiple times
    on_shutdown!(println!("shut down with success"));
    on_shutdown!({println!("blocks also work")});
    // some code ...
}