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Merge pull request #191 from Kuadrant/atomic-expiring-value
AtomicExpiringValue
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,144 @@ | ||
| use std::sync::atomic::Ordering; | ||
| use std::sync::atomic::{AtomicI64, AtomicU64}; | ||
| use std::time::{Duration, SystemTime, UNIX_EPOCH}; | ||
|
|
||
| #[derive(Debug)] | ||
| pub(crate) struct AtomicExpiringValue { | ||
| value: AtomicI64, | ||
| expiry: AtomicU64, // in microseconds | ||
| } | ||
|
|
||
| impl AtomicExpiringValue { | ||
| pub fn new(value: i64, expiry: SystemTime) -> Self { | ||
| let expiry = Self::get_duration_micros(expiry); | ||
| Self { | ||
| value: AtomicI64::new(value), | ||
| expiry: AtomicU64::new(expiry), | ||
| } | ||
| } | ||
|
|
||
| pub fn value_at(&self, when: SystemTime) -> i64 { | ||
| let when = Self::get_duration_micros(when); | ||
| let expiry = self.expiry.load(Ordering::SeqCst); | ||
| if expiry <= when { | ||
| return 0; | ||
| } | ||
| self.value.load(Ordering::SeqCst) | ||
| } | ||
|
|
||
| pub fn value(&self) -> i64 { | ||
| self.value_at(SystemTime::now()) | ||
| } | ||
|
|
||
| pub fn update(&self, delta: i64, ttl: u64, when: SystemTime) -> i64 { | ||
| let ttl_micros = ttl * 1_000_000; | ||
| let when_micros = Self::get_duration_micros(when); | ||
|
|
||
| let expiry = self.expiry.load(Ordering::SeqCst); | ||
| if expiry <= when_micros { | ||
| let new_expiry = when_micros + ttl_micros; | ||
| if self | ||
| .expiry | ||
| .compare_exchange(expiry, new_expiry, Ordering::SeqCst, Ordering::SeqCst) | ||
| .is_ok() | ||
| { | ||
| self.value.store(delta, Ordering::SeqCst); | ||
| } | ||
| return delta; | ||
| } | ||
| self.value.fetch_add(delta, Ordering::SeqCst) + delta | ||
| } | ||
|
|
||
| pub fn ttl(&self) -> Duration { | ||
| let expiry = | ||
| SystemTime::UNIX_EPOCH + Duration::from_micros(self.expiry.load(Ordering::SeqCst)); | ||
| expiry | ||
| .duration_since(SystemTime::now()) | ||
| .unwrap_or(Duration::ZERO) | ||
| } | ||
|
|
||
| fn get_duration_micros(when: SystemTime) -> u64 { | ||
| when.duration_since(UNIX_EPOCH) | ||
| .expect("SystemTime before UNIX EPOCH!") | ||
| .as_micros() as u64 | ||
| } | ||
| } | ||
|
|
||
| impl Default for AtomicExpiringValue { | ||
| fn default() -> Self { | ||
| AtomicExpiringValue { | ||
| value: AtomicI64::new(0), | ||
| expiry: AtomicU64::new(0), | ||
| } | ||
| } | ||
| } | ||
|
|
||
| impl Clone for AtomicExpiringValue { | ||
| fn clone(&self) -> Self { | ||
| AtomicExpiringValue { | ||
| value: AtomicI64::new(self.value.load(Ordering::SeqCst)), | ||
| expiry: AtomicU64::new(self.expiry.load(Ordering::SeqCst)), | ||
| } | ||
| } | ||
| } | ||
|
|
||
| #[cfg(test)] | ||
| mod tests { | ||
| use super::*; | ||
| use std::thread; | ||
| use std::time::{Duration, SystemTime}; | ||
|
|
||
| #[test] | ||
| fn returns_value_when_valid() { | ||
| let now = SystemTime::now(); | ||
| let val = AtomicExpiringValue::new(42, now); | ||
| assert_eq!(val.value_at(now - Duration::from_secs(1)), 42); | ||
| } | ||
|
|
||
| #[test] | ||
| fn returns_default_when_expired() { | ||
| let now = SystemTime::now(); | ||
| let val = AtomicExpiringValue::new(42, now - Duration::from_secs(1)); | ||
| assert_eq!(val.value_at(now), 0); | ||
| } | ||
|
|
||
| #[test] | ||
| fn returns_default_on_expiry() { | ||
| let now = SystemTime::now(); | ||
| let val = AtomicExpiringValue::new(42, now); | ||
| assert_eq!(val.value_at(now), 0); | ||
| } | ||
|
|
||
| #[test] | ||
| fn updates_when_valid() { | ||
| let now = SystemTime::now(); | ||
| let val = AtomicExpiringValue::new(42, now + Duration::from_secs(1)); | ||
| val.update(3, 10, now); | ||
| assert_eq!(val.value_at(now - Duration::from_secs(1)), 45); | ||
| } | ||
|
|
||
| #[test] | ||
| fn updates_when_expired() { | ||
| let now = SystemTime::now(); | ||
| let val = AtomicExpiringValue::new(42, now); | ||
| assert_eq!(val.ttl(), Duration::ZERO); | ||
| val.update(3, 10, now); | ||
| assert_eq!(val.value_at(now - Duration::from_secs(1)), 3); | ||
| } | ||
|
|
||
| #[test] | ||
| fn test_overlapping_updates() { | ||
| let now = SystemTime::now(); | ||
| let atomic_expiring_value = AtomicExpiringValue::new(42, now + Duration::from_secs(10)); | ||
|
|
||
| thread::scope(|s| { | ||
| s.spawn(|| { | ||
| atomic_expiring_value.update(1, 1, now); | ||
| }); | ||
| s.spawn(|| { | ||
| atomic_expiring_value.update(2, 1, now + Duration::from_secs(11)); | ||
| }); | ||
| }); | ||
| assert!([2i64, 3i64].contains(&atomic_expiring_value.value.load(Ordering::SeqCst))); | ||
| } | ||
| } |
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