rate_net/
algorithm.rs

1//! The rate-limiting algorithm a limiter applies.
2
3/// Selects the algorithm a limiter uses to decide a request.
4///
5/// Every algorithm shares the same [`Limiter`](crate::Limiter) surface, so the
6/// strategy can change without touching call sites. This enum is the selector a
7/// future builder uses to pick between them.
8///
9/// `#[non_exhaustive]`: algorithms are added over the `0.x` series, so a `match`
10/// must include a wildcard arm. [`TokenBucket`](Self::TokenBucket) — the default
11/// — is always available; the leaky bucket and the window algorithms are
12/// compiled in under the `algorithms` feature, so their variants only exist when
13/// it is enabled.
14///
15/// # Examples
16///
17/// ```
18/// use rate_net::Algorithm;
19///
20/// // The default is the token bucket — smooth refill with burst headroom.
21/// assert_eq!(Algorithm::default(), Algorithm::TokenBucket);
22/// ```
23#[non_exhaustive]
24#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Default)]
25pub enum Algorithm {
26    /// Smooth refill with burst headroom up to the configured capacity. The
27    /// general-purpose default; delegates its accounting to `better-bucket`.
28    #[default]
29    TokenBucket,
30    /// Constant-drain shaping that smooths bursts to a steady output rate.
31    /// Requires the `algorithms` feature.
32    #[cfg(feature = "algorithms")]
33    LeakyBucket,
34    /// A counter that resets each window; cheapest, tolerates boundary bursts.
35    /// Requires the `algorithms` feature.
36    #[cfg(feature = "algorithms")]
37    FixedWindow,
38    /// Exact request timestamps within the trailing window; highest accuracy,
39    /// higher memory. Requires the `algorithms` feature.
40    #[cfg(feature = "algorithms")]
41    SlidingWindowLog,
42    /// A weighted blend of the current and previous window; an accuracy/cost
43    /// balance and a common production choice. Requires the `algorithms` feature.
44    #[cfg(feature = "algorithms")]
45    SlidingWindowCounter,
46}
47
48#[cfg(test)]
49mod tests {
50    use super::Algorithm;
51
52    #[test]
53    fn test_default_is_token_bucket() {
54        assert_eq!(Algorithm::default(), Algorithm::TokenBucket);
55    }
56
57    #[cfg(feature = "algorithms")]
58    #[test]
59    fn test_variants_are_distinct() {
60        assert_ne!(Algorithm::TokenBucket, Algorithm::LeakyBucket);
61        assert_ne!(Algorithm::FixedWindow, Algorithm::SlidingWindowLog);
62    }
63}
rate_net/algorithm.rs

rate_net/
algorithm.rs
