zrx_stream/stream/operator/
throttle.rs

1// Copyright (c) Zensical LLC <https://zensical.org>
2
3// SPDX-License-Identifier: MIT
4// Third-party contributions licensed under CLA
5
6// Permission is hereby granted, free of charge, to any person obtaining a copy
7// of this software and associated documentation files (the "Software"), to
8// deal in the Software without restriction, including without limitation the
9// rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
10// sell copies of the Software, and to permit persons to whom the Software is
11// furnished to do so, subject to the following conditions:
12
13// The above copyright notice and this permission notice shall be included in
14// all copies or substantial portions of the Software.
15
16// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
17// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
18// FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL THE
19// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
20// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
21// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
22// IN THE SOFTWARE.
23
24// ----------------------------------------------------------------------------
25
26//! Throttle operator.
27
28use std::marker::PhantomData;
29use zrx_scheduler::action::descriptor::Property;
30use zrx_scheduler::action::output::IntoOutputs;
31use zrx_scheduler::action::Descriptor;
32use zrx_scheduler::effect::timer::IntoDuration;
33use zrx_scheduler::effect::{Item, Timer};
34use zrx_scheduler::{outputs, Id, Value};
35
36use crate::stream::function::SelectFn;
37use crate::stream::Stream;
38
39use super::{Operator, OperatorExt};
40
41// ----------------------------------------------------------------------------
42// Structs
43// ----------------------------------------------------------------------------
44
45/// Throttle operator.
46struct Throttle<F, D> {
47    /// Operator function.
48    function: F,
49    /// Type marker.
50    marker: PhantomData<D>,
51}
52
53// ----------------------------------------------------------------------------
54// Implementations
55// ----------------------------------------------------------------------------
56
57impl<I, T> Stream<I, T>
58where
59    I: Id,
60    T: Value + Clone,
61{
62    pub fn throttle<D>(&self, duration: D) -> Stream<I, T>
63    where
64        D: IntoDuration,
65    {
66        let duration = duration.into_duration();
67        self.with_operator(Throttle {
68            function: move |_: &T| duration,
69            marker: PhantomData,
70        })
71    }
72
73    pub fn throttle_with<F, D>(&self, f: F) -> Stream<I, T>
74    where
75        F: SelectFn<I, T, D>,
76        D: IntoDuration,
77    {
78        self.with_operator(Throttle {
79            function: f,
80            marker: PhantomData,
81        })
82    }
83}
84
85// ----------------------------------------------------------------------------
86// Trait implementations
87// ----------------------------------------------------------------------------
88
89impl<I, T, F, D> Operator<I, T> for Throttle<F, D>
90where
91    I: Id,
92    T: Value + Clone,
93    F: SelectFn<I, T, D>,
94    D: IntoDuration,
95{
96    type Item<'a> = Item<&'a I, &'a T>;
97
98    /// Handles the given item.
99    ///
100    /// Throttling is implemented with the help of two timers, where the first
101    /// timer acts as a guard to ensure that the second timer is only set if the
102    /// first timer hasn't already been set. The most recent item is emitted
103    /// only if the second timer isn't active.
104    #[cfg_attr(
105        feature = "tracing",
106        tracing::instrument(level = "debug", skip_all, fields(id = %item.id))
107    )]
108    fn handle(&mut self, item: Self::Item<'_>) -> impl IntoOutputs<I> {
109        self.function.execute(item.id, item.data).map(|report| {
110            report.map(|duration| {
111                let timer = Timer::set(duration, None);
112                Timer::set(
113                    0,
114                    Some(outputs![timer, item.into_owned().map(Some)]),
115                )
116            })
117        })
118    }
119
120    /// Returns the descriptor.
121    #[inline]
122    fn descriptor(&self) -> Descriptor {
123        Descriptor::builder()
124            .property(Property::Pure)
125            .property(Property::Stable)
126            .property(Property::Flush)
127            .build()
128    }
129}
zrx_stream/stream/operator/throttle.rs

zrx_stream/stream/operator/
throttle.rs
