foyer_common/
rate.rs

1// Copyright 2026 foyer Project Authors
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7//     http://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14
15use std::time::{Duration, Instant};
16
17use parking_lot::Mutex;
18
19/// A rate limiter that returns the wait duration for limitation.
20#[derive(Debug)]
21pub struct RateLimiter {
22    inner: Mutex<Inner>,
23    rate: f64,
24}
25
26#[derive(Debug)]
27struct Inner {
28    quota: f64,
29
30    last: Instant,
31}
32
33impl RateLimiter {
34    /// Create a rate limiter that returns the wait duration for limitation.
35    pub fn new(rate: f64) -> Self {
36        let inner = Inner {
37            quota: 0.0,
38            last: Instant::now(),
39        };
40        Self {
41            rate,
42            inner: Mutex::new(inner),
43        }
44    }
45
46    /// Consume some quota from the rate limiter.
47    ///
48    /// If there is not enough quota left, return a duration for the caller to wait.
49    /// Otherwise, return [`Duration::ZERO`] indicating no need to wait.
50    pub fn consume(&self, weight: f64) -> Duration {
51        let mut inner = self.inner.lock();
52        let now = Instant::now();
53        let refill = now.duration_since(inner.last).as_secs_f64() * self.rate;
54        inner.last = now;
55        inner.quota = f64::min(inner.quota + refill, self.rate);
56        inner.quota -= weight;
57        if inner.quota >= 0.0 {
58            return Duration::ZERO;
59        }
60        Duration::from_secs_f64((-inner.quota) / self.rate)
61    }
62}
63
64#[cfg(test)]
65mod tests {
66    use std::sync::{
67        atomic::{AtomicUsize, Ordering},
68        Arc,
69    };
70
71    use rand::{rng, Rng};
72
73    use super::*;
74
75    const ERATIO: f64 = 0.05;
76    const THREADS: usize = 8;
77    const RATE: usize = 1000;
78    const DURATION: Duration = Duration::from_secs(10);
79
80    #[ignore]
81    #[test]
82    fn test_rate_limiter() {
83        let v = Arc::new(AtomicUsize::new(0));
84        let limiter = Arc::new(RateLimiter::new(RATE as f64));
85        let task = |rate: usize, v: Arc<AtomicUsize>, limiter: Arc<RateLimiter>| {
86            let start = Instant::now();
87            loop {
88                if start.elapsed() >= DURATION {
89                    break;
90                }
91                let dur = limiter.consume(rate as f64);
92                if !dur.is_zero() {
93                    std::thread::sleep(dur);
94                }
95                v.fetch_add(rate, Ordering::Relaxed);
96            }
97        };
98        let mut handles = vec![];
99        let mut rng = rng();
100        for _ in 0..THREADS {
101            let rate = rng.random_range(10..20);
102            let handle = std::thread::spawn({
103                let v = v.clone();
104                let limiter = limiter.clone();
105                move || task(rate, v, limiter)
106            });
107            handles.push(handle);
108        }
109
110        for handle in handles {
111            handle.join().unwrap();
112        }
113
114        let error = (v.load(Ordering::Relaxed) as isize - RATE as isize * DURATION.as_secs() as isize).unsigned_abs();
115        let eratio = error as f64 / (RATE as f64 * DURATION.as_secs_f64());
116        assert!(eratio < ERATIO, "eratio: {eratio}, target: {ERATIO}");
117        println!("eratio {eratio} < ERATIO {ERATIO}");
118    }
119}
foyer_common/rate.rs

foyer_common/
rate.rs
