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//! # shutdown
//!
//! This crate is meant to be used together with Tokio as it provides an
//! async solution for listening and forwarding shutdown signals.
//!
//! When creating a new "root" shutdown signal, it will register itself to
//! listen for SIGINT and SIGTERM signals. When a SIGNINT or SIGTERM is received,
//! it will unregister itself again so any additional signals will be processed
//! as usual (interrupting or terminating the process in most cases). Besides a
//! SIGINT or SIGTERM signal, you can also trigger a shutdown signal manually by
//! calling [signal](Shutdown::signal).
//!
//! You can form a tree of branches and subscribers and choose to only shutdown
//! a specific branch. This will shutdown all subscribers but also any child
//! branches and their subscribers. This can be helpful in async applications
//! where lots of tasks spawn lots of tasks, that spawn lots of tasks...
use std::sync::{atomic::AtomicBool, Arc};
use futures::stream::StreamExt;
use log::debug;
use signal_hook::{
consts::{SIGINT, SIGTERM},
flag,
};
use signal_hook_tokio::Signals;
use tokio_util::sync::CancellationToken;
#[derive(Debug)]
pub struct Shutdown {
token: CancellationToken,
}
impl Clone for Shutdown {
fn clone(&self) -> Self {
self.subscribe()
}
}
impl Shutdown {
/// Create a new shutdown signal. In most cases the signal will be
/// triggered when CTRL-C is pressed and the process receives a SIGINT or
/// SIGTERM signal. If needed you can also call [signal](Shutdown::signal)
/// to send a shutdown signal programmatically.
///
/// # Examples
///
/// ```no_run
/// use shutdown::Shutdown;
///
/// let root = Shutdown::new().unwrap();
/// ```
pub fn new() -> Result<Self, std::io::Error> {
// Create a cancellation token.
let token = CancellationToken::new();
// Create a new shutdown signal.
let shutdown = Self {
token: token.clone(),
};
// Register the SIGINT and SIGTERM signals.
let mut signals = Signals::new([SIGINT, SIGTERM])?;
// Spawn a Tokio task that will listen for signals.
tokio::spawn(async move {
if let Some(signal) = signals.next().await {
debug!("Received a shutdown signal: {}", signal);
// Register conditional shutdown handlers. This makes sure the
// application will terminate after receiving a second signal.
flag::register_conditional_shutdown(SIGINT, 0, Arc::new(AtomicBool::new(true)))
.unwrap();
flag::register_conditional_shutdown(SIGTERM, 0, Arc::new(AtomicBool::new(true)))
.unwrap();
// Send the shutdown signal by cancelling the token.
token.cancel();
}
});
Ok(shutdown)
}
/// Create a new branch (child) that can be signalled independent of the
/// root (parent). When the root (or parent to be more precise) is signalled,
/// the new branch (and any child branches) will also be signalled.
///
/// # Examples
///
/// ```no_run
/// use shutdown::Shutdown;
///
/// let root = Shutdown::new().unwrap();
/// let branch = root.branch();
///
/// // Signal a specific branch
/// branch.signal();
/// ```
pub fn branch(&self) -> Self {
Self {
token: self.token.child_token(),
}
}
/// Create a new subscriber (sibling) that listens to an existing root (or
/// previously created branch) for any shutdown signals.
///
/// # Examples
///
/// ```no_run
/// use shutdown::Shutdown;
///
/// let root = Shutdown::new().unwrap();
/// let subscriber = root.subscribe();
/// ```
pub fn subscribe(&self) -> Self {
Self {
token: self.token.clone(),
}
}
/// Returns `true` if a shutdown signal has been received.
///
/// # Examples
///
/// ```no_run
/// use shutdown::Shutdown;
///
/// let root = Shutdown::new().unwrap();
///
/// while !root.is_signalled() {
/// // Do stuff...
/// }
/// ```
pub fn is_signalled(&self) -> bool {
self.token.is_cancelled()
}
/// Manually signal the root or a branch. This causes all connected
/// subscribers and any child branches to be signalled as well.
///
/// # Examples
///
/// ```no_run
/// use shutdown::Shutdown;
///
/// let root = Shutdown::new().unwrap();
/// let branch = root.branch();
///
/// // Trigger a signal from code
/// root.signal();
/// ```
pub fn signal(&self) {
self.token.cancel();
}
/// Block until a shutdown signal is received. This can, for example, be
/// used in a select to block to wait for a long running task while still
/// being able to respond to a shutdown signal.
///
/// # Examples
///
/// ```no_run
/// use shutdown::Shutdown;
/// use tokio::time::{sleep, Duration};
///
/// #[tokio::main]
/// async fn main() {
/// let mut root = Shutdown::new().unwrap();
///
/// tokio::select! {
/// _ = root.signalled() => (),
/// _ = sleep(Duration::from_secs(300)) => (), // Long runnnig task
/// }
/// }
/// ```
pub async fn signalled(&self) {
self.token.cancelled().await;
}
}
#[cfg(test)]
mod tests {
use super::*;
use tokio::time::{sleep, Duration};
#[tokio::test]
async fn not_notified() {
let _ = env_logger::Builder::new()
.format_timestamp(None)
.filter(None, log::LevelFilter::Debug)
.is_test(true)
.try_init();
let root = Shutdown::new().unwrap();
let branch1 = root.branch();
let branch2 = branch1.branch();
let sub1 = branch1.subscribe();
let sub2 = branch2.subscribe();
tokio::select! {
_ = root.signalled() => (),
_ = sleep(Duration::from_secs(1)) => (),
}
assert!(!root.is_signalled(), "root shutdown without notify");
assert!(!branch1.is_signalled(), "branch1 shutdown without notify");
assert!(!branch2.is_signalled(), "branch2 shutdown without notify");
assert!(!sub1.is_signalled(), "subscriber1 shutdown without notify");
assert!(!sub2.is_signalled(), "subscriber2 shutdown without notify");
}
#[tokio::test]
async fn shutdown_sigint() {
let _ = env_logger::Builder::new()
.format_timestamp(None)
.filter(None, log::LevelFilter::Debug)
.is_test(true)
.try_init();
let root = Shutdown::new().unwrap();
let branch1 = root.branch();
let branch2 = branch1.branch();
let sub1 = branch1.subscribe();
let sub2 = branch2.subscribe();
unsafe { libc::raise(signal_hook::consts::SIGINT) };
tokio::select! {
_ = root.signalled() => (),
_ = sleep(Duration::from_secs(1)) => (),
}
tokio::select! {
_ = sub1.signalled() => (),
_ = sleep(Duration::from_secs(1)) => (),
}
tokio::select! {
_ = sub2.signalled() => (),
_ = sleep(Duration::from_secs(1)) => (),
}
assert!(root.is_signalled(), "root not shutdown (signal)");
assert!(branch1.is_signalled(), "branch1 not shutdown (signal)");
assert!(branch2.is_signalled(), "branch2 not shutdown (signal)");
assert!(sub1.is_signalled(), "subscriber1 not shutdown (signal)");
assert!(sub2.is_signalled(), "subscriber2 not shutdown (signal)");
}
#[tokio::test]
async fn shutdown_now() {
let root = Shutdown::new().unwrap();
let branch1 = root.branch();
let branch2 = branch1.branch();
let sub1 = branch1.subscribe();
let sub2 = branch2.subscribe();
root.signal();
tokio::select! {
_ = root.signalled() => (),
_ = sleep(Duration::from_secs(1)) => (),
}
tokio::select! {
_ = sub1.signalled() => (),
_ = sleep(Duration::from_secs(1)) => (),
}
tokio::select! {
_ = sub2.signalled() => (),
_ = sleep(Duration::from_secs(1)) => (),
}
assert!(root.is_signalled(), "root not shutdown (manual)");
assert!(branch1.is_signalled(), "branch1 not shutdown (manual)");
assert!(branch2.is_signalled(), "branch2 not shutdown (manual)");
assert!(sub1.is_signalled(), "subscriber1 not shutdown (manual)");
assert!(sub2.is_signalled(), "subscriber2 not shutdown (manual)");
}
#[tokio::test]
async fn shutdown_branch() {
let root = Shutdown::new().unwrap();
let branch1 = root.branch();
let branch2 = branch1.branch();
let sub1 = branch1.subscribe();
let sub2 = branch2.subscribe();
sub2.signal();
tokio::select! {
_ = root.signalled() => (),
_ = sleep(Duration::from_secs(1)) => (),
}
tokio::select! {
_ = sub1.signalled() => (),
_ = sleep(Duration::from_secs(1)) => (),
}
tokio::select! {
_ = sub2.signalled() => (),
_ = sleep(Duration::from_secs(1)) => (),
}
assert!(!root.is_signalled(), "root shutdown without notify");
assert!(!branch1.is_signalled(), "branch1 shutdown without notify");
assert!(!sub1.is_signalled(), "subscriber1 shutdown without notify");
assert!(branch2.is_signalled(), "branch2 not shutdown (manual)");
assert!(sub2.is_signalled(), "subscriber2 not shutdown (manual)");
}
}