reth_tracing/
throttle.rs

1//! Throttling utilities for rate-limiting expression execution.
2
3use std::{
4    sync::{
5        atomic::{AtomicU64, Ordering},
6        LazyLock,
7    },
8    time::Instant,
9};
10
11/// Sentinel value indicating the throttle has never run.
12#[doc(hidden)]
13pub const NOT_YET_RUN: u64 = u64::MAX;
14
15/// Checks if enough time has passed since the last run. Implementation detail for [`throttle!`].
16#[doc(hidden)]
17pub fn should_run(start: &LazyLock<Instant>, last: &AtomicU64, duration_millis: u64) -> bool {
18    let now = start.elapsed().as_millis() as u64;
19    let last_val = last.load(Ordering::Relaxed);
20
21    if last_val == NOT_YET_RUN {
22        return last
23            .compare_exchange(NOT_YET_RUN, now, Ordering::Relaxed, Ordering::Relaxed)
24            .is_ok();
25    }
26
27    if now.saturating_sub(last_val) >= duration_millis {
28        last.compare_exchange(last_val, now, Ordering::Relaxed, Ordering::Relaxed).is_ok()
29    } else {
30        false
31    }
32}
33
34/// Throttles the execution of an expression to run at most once per specified duration.
35///
36/// Uses static variables with lazy initialization to track the last execution time.
37/// Thread-safe via atomic operations.
38///
39/// # Examples
40///
41/// ```ignore
42/// use std::time::Duration;
43/// use reth_tracing::throttle;
44///
45/// // Log at most once per second.
46/// throttle!(Duration::from_secs(1), || {
47///     tracing::info!("This message is throttled");
48/// });
49/// ```
50#[deprecated(
51    note = "no longer used by reth and scheduled for removal, copy the macro if you depend on it"
52)]
53#[macro_export]
54macro_rules! throttle {
55    ($duration:expr, || $expr:expr) => {{
56        static START: ::std::sync::LazyLock<::std::time::Instant> =
57            ::std::sync::LazyLock::new(::std::time::Instant::now);
58        static LAST: ::core::sync::atomic::AtomicU64 =
59            ::core::sync::atomic::AtomicU64::new($crate::__private::NOT_YET_RUN);
60
61        if $crate::__private::should_run(&START, &LAST, $duration.as_millis() as u64) {
62            $expr
63        }
64    }};
65}
66
67#[cfg(test)]
68#[allow(deprecated)]
69mod tests {
70    use std::sync::atomic::{AtomicUsize, Ordering};
71
72    #[test]
73    fn test_throttle_runs_once_initially() {
74        static COUNTER: AtomicUsize = AtomicUsize::new(0);
75
76        throttle!(std::time::Duration::from_secs(10), || {
77            COUNTER.fetch_add(1, Ordering::SeqCst);
78        });
79
80        assert_eq!(COUNTER.load(Ordering::SeqCst), 1);
81    }
82}
reth_tracing/throttle.rs

reth_tracing/
throttle.rs
