nautilus_network/ratelimiter/
quota.rs

1// -------------------------------------------------------------------------------------------------
2//  Copyright (C) 2015-2026 Nautech Systems Pty Ltd. All rights reserved.
3//  https://nautechsystems.io
4//
5//  Licensed under the GNU Lesser General Public License Version 3.0 (the "License");
6//  You may not use this file except in compliance with the License.
7//  You may obtain a copy of the License at https://www.gnu.org/licenses/lgpl-3.0.en.html
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// -------------------------------------------------------------------------------------------------
15
16use std::{num::NonZeroU32, prelude::v1::*, time::Duration};
17
18use super::nanos::Nanos;
19
20/// A rate-limiting quota.
21///
22/// Quotas are expressed in a positive number of "cells" (the maximum number of positive decisions /
23/// allowed items until the rate limiter needs to replenish) and the amount of time for the rate
24/// limiter to replenish a single cell.
25///
26/// Neither the number of cells nor the replenishment unit of time may be zero.
27///
28/// # Burst Sizes
29/// There are multiple ways of expressing the same quota: a quota given as `Quota::per_second(1)`
30/// allows, on average, the same number of cells through as a quota given as `Quota::per_minute(60)`.
31/// The quota of `Quota::per_minute(60)` has a burst size of 60 cells, meaning it is
32/// possible to accommodate 60 cells in one go, after which the equivalent of a minute of inactivity
33/// is required for the burst allowance to be fully restored.
34///
35/// Burst size gets really important when you construct a rate limiter that should allow multiple
36/// elements through at one time (using [`RateLimiter.check_n`](struct.RateLimiter.html#method.check_n)
37/// and its related functions): Only
38/// at most as many cells can be let through in one call as are given as the burst size.
39///
40/// In other words, the burst size is the maximum number of cells that the rate limiter will ever
41/// allow through without replenishing them.
42#[derive(Debug, PartialEq, Eq, Clone, Copy)]
43#[cfg_attr(
44    feature = "python",
45    pyo3::pyclass(module = "nautilus_trader.core.nautilus_pyo3.network")
46)]
47pub struct Quota {
48    pub(crate) max_burst: NonZeroU32,
49    pub(crate) replenish_1_per: Duration,
50}
51
52/// Constructors for Quotas
53impl Quota {
54    /// Construct a quota for a number of cells per second. The given number of cells is also
55    /// assumed to be the maximum burst size.
56    #[must_use]
57    pub const fn per_second(max_burst: NonZeroU32) -> Self {
58        let replenish_interval_ns = Duration::from_secs(1).as_nanos() / (max_burst.get() as u128);
59        Self {
60            max_burst,
61            replenish_1_per: Duration::from_nanos(replenish_interval_ns as u64),
62        }
63    }
64
65    /// Construct a quota for a number of cells per 60-second period. The given number of cells is
66    /// also assumed to be the maximum burst size.
67    #[must_use]
68    pub const fn per_minute(max_burst: NonZeroU32) -> Self {
69        let replenish_interval_ns = Duration::from_secs(60).as_nanos() / (max_burst.get() as u128);
70        Self {
71            max_burst,
72            replenish_1_per: Duration::from_nanos(replenish_interval_ns as u64),
73        }
74    }
75
76    /// Construct a quota for a number of cells per 60-minute (3600-second) period. The given number
77    /// of cells is also assumed to be the maximum burst size.
78    #[must_use]
79    pub const fn per_hour(max_burst: NonZeroU32) -> Self {
80        let replenish_interval_ns =
81            Duration::from_secs(60 * 60).as_nanos() / (max_burst.get() as u128);
82        Self {
83            max_burst,
84            replenish_1_per: Duration::from_nanos(replenish_interval_ns as u64),
85        }
86    }
87
88    /// Construct a quota that replenishes one cell in a given
89    /// interval.
90    ///
91    /// This constructor is meant to replace [`::new`](#method.new),
92    /// in cases where a longer refresh period than 1 cell/hour is
93    /// necessary.
94    ///
95    /// If the time interval is zero, returns `None`.
96    #[must_use]
97    pub const fn with_period(replenish_1_per: Duration) -> Option<Self> {
98        if replenish_1_per.as_nanos() == 0 {
99            None
100        } else {
101            // SAFETY: Unwrap is safe because 1 is always non-zero
102            #[allow(clippy::missing_panics_doc)]
103            Some(Self {
104                max_burst: NonZeroU32::new(1).unwrap(),
105                replenish_1_per,
106            })
107        }
108    }
109
110    /// Adjusts the maximum burst size for a quota to construct a rate limiter with a capacity
111    /// for at most the given number of cells.
112    #[must_use]
113    pub const fn allow_burst(self, max_burst: NonZeroU32) -> Self {
114        Self { max_burst, ..self }
115    }
116
117    /// Construct a quota for a given burst size, replenishing the entire burst size in that
118    /// given unit of time.
119    ///
120    /// Returns `None` if the duration is zero.
121    ///
122    /// This constructor allows greater control over the resulting
123    /// quota, but doesn't make as much intuitive sense as other
124    /// methods of constructing the same quotas. Unless your quotas
125    /// are given as "max burst size, and time it takes to replenish
126    /// that burst size", you are better served by the
127    /// [`Quota::per_second`](#method.per_second) (and similar)
128    /// constructors with the [`allow_burst`](#method.allow_burst)
129    /// modifier.
130    #[deprecated(
131        since = "0.2.0",
132        note = "This constructor is often confusing and non-intuitive. \
133    Use the `per_(interval)` / `with_period` and `max_burst` constructors instead."
134    )]
135    #[must_use]
136    pub fn new(max_burst: NonZeroU32, replenish_all_per: Duration) -> Option<Self> {
137        if replenish_all_per.as_nanos() == 0 {
138            None
139        } else {
140            Some(Self {
141                max_burst,
142                replenish_1_per: replenish_all_per / max_burst.get(),
143            })
144        }
145    }
146}
147
148/// Retrieving information about a quota
149impl Quota {
150    /// The time it takes for a rate limiter with an exhausted burst budget to replenish
151    /// a single element.
152    #[must_use]
153    pub const fn replenish_interval(&self) -> Duration {
154        self.replenish_1_per
155    }
156
157    /// The maximum number of cells that can be allowed in one burst.
158    #[must_use]
159    pub const fn burst_size(&self) -> NonZeroU32 {
160        self.max_burst
161    }
162
163    /// The time it takes to replenish the entire maximum burst size.
164    #[must_use]
165    pub const fn burst_size_replenished_in(&self) -> Duration {
166        let fill_in_ns = self.replenish_1_per.as_nanos() * self.max_burst.get() as u128;
167        Duration::from_nanos(fill_in_ns as u64)
168    }
169}
170
171impl Quota {
172    /// A way to reconstruct a Quota from an in-use Gcra.
173    ///
174    /// This is useful mainly for [`crate::middleware::RateLimitingMiddleware`]
175    /// where custom code may want to construct information based on
176    /// the amount of burst balance remaining.
177    ///
178    /// # Panics
179    ///
180    /// Panics if the division result is 0 or exceeds `u32::MAX`.
181    pub(crate) fn from_gcra_parameters(t: Nanos, tau: Nanos) -> Self {
182        let t_u64 = t.as_u64();
183        let tau_u64 = tau.as_u64();
184
185        // Validate division won't be zero or overflow
186        assert!(t_u64 != 0, "Invalid GCRA parameter: t cannot be zero");
187
188        let division_result = tau_u64 / t_u64;
189        assert!(
190            division_result != 0,
191            "Invalid GCRA parameters: tau/t results in zero burst capacity"
192        );
193        assert!(
194            u32::try_from(division_result).is_ok(),
195            "Invalid GCRA parameters: tau/t exceeds u32::MAX"
196        );
197
198        // We've verified the result is non-zero and fits in u32
199        let max_burst = NonZeroU32::new(division_result as u32)
200            .expect("Division result should be non-zero after validation");
201        let replenish_1_per = t.into();
202        Self {
203            max_burst,
204            replenish_1_per,
205        }
206    }
207}
208
209// #[cfg(test)]
210// mod test {
211//     use nonzero_ext::nonzero;
212
213//     use super::*;
214//     use rstest::rstest;
215
216//     #[rstest]
217//     fn time_multiples() {
218//         let hourly = Quota::per_hour(nonzero!(1u32));
219//         let minutely = Quota::per_minute(nonzero!(1u32));
220//         let secondly = Quota::per_second(nonzero!(1u32));
221
222//         assert_eq!(
223//             hourly.replenish_interval() / 60,
224//             minutely.replenish_interval()
225//         );
226//         assert_eq!(
227//             minutely.replenish_interval() / 60,
228//             secondly.replenish_interval()
229//         );
230//     }
231
232//     #[rstest]
233//     fn period_error_cases() {
234//         assert!(Quota::with_period(Duration::from_secs(0)).is_none());
235
236//         #[allow(deprecated)]
237//         {
238//             assert!(Quota::new(nonzero!(1u32), Duration::from_secs(0)).is_none());
239//         }
240//     }
241// }
nautilus_network/ratelimiter/quota.rs

nautilus_network/ratelimiter/
quota.rs
