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//! Types and code to track the readiness status of a fallback directory.
use std::time::{Duration, Instant};
use tor_basic_utils::retry::RetryDelay;
/// Status information about whether a [`FallbackDir`](super::FallbackDir) is
/// currently usable.
///
/// This structure is used to track whether the fallback cache has recently
/// failed, and if so, when it can be retried.
#[derive(Debug, Clone)]
pub(crate) struct Status {
/// Used to decide how long to delay before retrying a fallback cache
/// that has failed.
delay: RetryDelay,
/// A time before which we should assume that this fallback cache is broken.
///
/// If None, then this fallback cache is ready to use right away.
retry_at: Option<Instant>,
}
/// Least amount of time we'll wait before retrying a fallback cache.
//
// TODO: we may want to make this configurable to a smaller value for chutney networks.
const FALLBACK_RETRY_FLOOR: Duration = Duration::from_secs(150);
impl Default for Status {
fn default() -> Self {
Status {
delay: RetryDelay::from_duration(FALLBACK_RETRY_FLOOR),
retry_at: None,
}
}
}
impl Status {
/// Return true if this `Status` is usable at the time `now`.
pub(crate) fn usable_at(&self, now: Instant) -> bool {
match self.retry_at {
Some(ready) => now >= ready,
None => true,
}
}
/// Return the time at which this `Status` can next be retried.
///
/// A return value of `None`, or of a time in the past, indicates that this
/// status can be used immediately.
pub(crate) fn next_retriable(&self) -> Option<Instant> {
self.retry_at
}
/// Record that the associated fallback directory has been used successfully.
///
/// This should only be done after successfully handling a whole reply from the
/// directory.
pub(crate) fn note_success(&mut self) {
self.retry_at = None;
self.delay = RetryDelay::from_duration(FALLBACK_RETRY_FLOOR);
}
/// Record that the associated fallback directory has failed.
pub(crate) fn note_failure(&mut self, now: Instant) {
let mut rng = rand::thread_rng();
self.retry_at = Some(now + self.delay.next_delay(&mut rng));
}
}
#[cfg(test)]
mod test {
#![allow(clippy::unwrap_used)]
use super::*;
#[test]
fn status_basics() {
let now = Instant::now();
let mut status = Status::default();
// newly created status is usable.
assert!(status.usable_at(now));
// no longer usable after a failure.
status.note_failure(now);
assert_eq!(status.next_retriable().unwrap(), now + FALLBACK_RETRY_FLOOR);
assert!(!status.usable_at(now));
// Not enough time has passed.
assert!(!status.usable_at(now + FALLBACK_RETRY_FLOOR / 2));
// Enough time has passed.
assert!(status.usable_at(now + FALLBACK_RETRY_FLOOR));
// Mark as failed again; the timeout will (probably) be longer.
status.note_failure(now + FALLBACK_RETRY_FLOOR);
assert!(status.next_retriable().unwrap() >= now + FALLBACK_RETRY_FLOOR * 2);
assert!(!status.usable_at(now + FALLBACK_RETRY_FLOOR));
// Mark as succeeded; it should be usable immediately.
status.note_success();
assert!(status.usable_at(now + FALLBACK_RETRY_FLOOR));
}
}
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