Shutdown management for graceful shutdown of tokio applications. Guard creating and usage is lock-free and the crate only locks when:

the shutdwn signal was not yet given and you wait with a (weak or strong) guard on whether or not it was in fact canelled;
the check of whether or not the app can shuts down typically is locked until the shutdown signal was received and all (strong) guards were dropped.

This crate is written in 100% safe Rust code.

Examples

One example to show it all:

```rust use std::time::Duration; use tokio_graceful::Shutdown;

[tokio::main]

async fn main() { // most users can just use Shutdown::default() to initiate // shutdown upon either Sigterm or CTRL+C (Sigkill). let signal = tokio::time::sleep(std::time::Duration::from_millis(100)); let shutdown = Shutdown::new(signal);

// you can use shutdown to spawn tasks that will
// include a guard to prevent the shutdown from completing
// aslong as these tasks are open
shutdown.spawn_task(async {
    tokio::time::sleep(std::time::Duration::from_millis(10)).await;
});
// or spawn a function such that you have access to the guard coupled to the task
shutdown.spawn_task_fn(|guard| async move {
    let guard2 = guard.clone();
    guard.cancelled().await;
});

// this guard isn't dropped, but as it's a weak guard
// it has no impact on the ref count of the common tokens.
let guard_weak = shutdown.guard_weak();

// this guard needs to be dropped as otherwise the shutdown is prevented;
let guard = shutdown.guard();
drop(guard);

// guards can be downgraded to weak guards, to not have it be counted any longer in the ref count
let weak_guard_2 = shutdown.guard().downgrade();

// guards (weak or not) are cancel safe
tokio::select! {
    _ = tokio::time::sleep(std::time::Duration::from_millis(10)) => {},
    _ = weak_guard_2.into_cancelled() => {},
}

// you can also wait to shut down without any timeout limit
// `shutdown.shutdown().await;`
shutdown
    .shutdown_with_limit(Duration::from_secs(60))
    .await
    .unwrap();

// once a shutdown is triggered the ::cancelled() fn will immediately return true,
// forever, not just once. Even after shutdown process is completely finished.
guard_weak.cancelled().await;

// weak guards can be upgraded to regular guards to take into account for ref count
let guard = guard_weak.upgrade();
// even this one however will know it was cancelled
guard.cancelled().await;

}

```

Runnable Examples

While the above example shows pretty much all parts of this crate at once, it might be useful to see examples on how this crate is to be used in an actual production-like setting. That's what these runnable examples are for.

The runnable examples are best run with RUST_LOG=trace environment variable set, such that you see the verbose logs of tokio-graceful and really see it in action and get a sense on how it works, or at least its flow is.

examples/tokio_tcp.rs

bash RUST_LOG=trace cargo run --example tokio_tcp

The tokio_tcp example showcases the original use case of why tokio-graceful shutdown was developed, as it makes managing graceful shutdown from start to finish a lot easier, without immediately grabbing to big power tools or providing more then is needed.

The example runs a tcp 'echo' server which you can best play with using telnet: telnet 127.0.0.1 8080. As you are in control of when to exit you can easily let it timeout if you wish.

examples/hyper.rs

bash RUST_LOG=trace cargo run --example hyper

In case you wish to use this library as a Hyper user you can do so using pretty much the same approach as the Tokio tcp example.

This example only has one router server function which returns 'hello' (200 OK) after 5s. The delay is there to allow you to see the graceful shutdown in action.

Contributing

:balloon: Thanks for your help improving the project! We are so happy to have you! We have a contributing guide to help you get involved in the tokio-graceful project.

Shoutouts

Special shoutout for this library goes to the Tokio ecosystem. Those who developed it as well as the folks hanging on the Tokio discord server. The discussions and Q&A sessions with them were very crucial to the development of this project. Tokio's codebase is also a gem of examples on what is possible and what are good practices.

In this context also an extra shoutout to @tobz who gave me the idea of approaching it from an Atomic perspective instead of immediately going for channel solutions.

License

This project is dual-licensed under both the MIT license and Apache 2.0 License.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in tokio-graceful by you, shall be licensed as both MIT and Apache 2.0, without any additional terms or conditions.