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|
use std::{
cmp::min,
sync::atomic::{AtomicBool, AtomicU32, Ordering},
time::Duration,
};
use smol::Timer;
/// Exponential backoff
/// <https://en.wikipedia.org/wiki/Exponential_backoff>
///
/// # Examples
///
/// ```
/// use karyons_core::async_util::Backoff;
///
/// async {
/// let backoff = Backoff::new(300, 3000);
///
/// loop {
/// backoff.sleep().await;
///
/// // do something
/// break;
/// }
///
/// backoff.reset();
///
/// // ....
/// };
///
/// ```
///
pub struct Backoff {
/// The base delay in milliseconds for the initial retry.
base_delay: u64,
/// The max delay in milliseconds allowed for a retry.
max_delay: u64,
/// Atomic counter
retries: AtomicU32,
/// Stop flag
stop: AtomicBool,
}
impl Backoff {
/// Creates a new Backoff.
pub fn new(base_delay: u64, max_delay: u64) -> Self {
Self {
base_delay,
max_delay,
retries: AtomicU32::new(0),
stop: AtomicBool::new(false),
}
}
/// Sleep based on the current retry count and delay values.
/// Retruns the delay value.
pub async fn sleep(&self) -> u64 {
if self.stop.load(Ordering::SeqCst) {
Timer::after(Duration::from_millis(self.max_delay)).await;
return self.max_delay;
}
let retries = self.retries.load(Ordering::SeqCst);
let delay = self.base_delay * (2_u64).pow(retries);
let delay = min(delay, self.max_delay);
if delay == self.max_delay {
self.stop.store(true, Ordering::SeqCst);
}
self.retries.store(retries + 1, Ordering::SeqCst);
Timer::after(Duration::from_millis(delay)).await;
delay
}
/// Reset the retry counter to 0.
pub fn reset(&self) {
self.retries.store(0, Ordering::SeqCst);
self.stop.store(false, Ordering::SeqCst);
}
}
#[cfg(test)]
mod tests {
use super::*;
use std::sync::Arc;
#[test]
fn test_backoff() {
smol::block_on(async move {
let backoff = Arc::new(Backoff::new(5, 15));
let backoff_c = backoff.clone();
smol::spawn(async move {
let delay = backoff_c.sleep().await;
assert_eq!(delay, 5);
let delay = backoff_c.sleep().await;
assert_eq!(delay, 10);
let delay = backoff_c.sleep().await;
assert_eq!(delay, 15);
})
.await;
smol::spawn(async move {
backoff.reset();
let delay = backoff.sleep().await;
assert_eq!(delay, 5);
})
.await;
});
}
}
|
