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**/target
**/*.rs.bk
**/Cargo.lock
**/dhat-heap.json
.vscode
.cover

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[workspace]
members = [
"pingora-limits",
]

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Apache License
Version 2.0, January 2004
http://www.apache.org/licenses/
TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
1. Definitions.
"License" shall mean the terms and conditions for use, reproduction,
and distribution as defined by Sections 1 through 9 of this document.
"Licensor" shall mean the copyright owner or entity authorized by
the copyright owner that is granting the License.
"Legal Entity" shall mean the union of the acting entity and all
other entities that control, are controlled by, or are under common
control with that entity. For the purposes of this definition,
"control" means (i) the power, direct or indirect, to cause the
direction or management of such entity, whether by contract or
otherwise, or (ii) ownership of fifty percent (50%) or more of the
outstanding shares, or (iii) beneficial ownership of such entity.
"You" (or "Your") shall mean an individual or Legal Entity
exercising permissions granted by this License.
"Source" form shall mean the preferred form for making modifications,
including but not limited to software source code, documentation
source, and configuration files.
"Object" form shall mean any form resulting from mechanical
transformation or translation of a Source form, including but
not limited to compiled object code, generated documentation,
and conversions to other media types.
"Work" shall mean the work of authorship, whether in Source or
Object form, made available under the License, as indicated by a
copyright notice that is included in or attached to the work
(an example is provided in the Appendix below).
"Derivative Works" shall mean any work, whether in Source or Object
form, that is based on (or derived from) the Work and for which the
editorial revisions, annotations, elaborations, or other modifications
represent, as a whole, an original work of authorship. For the purposes
of this License, Derivative Works shall not include works that remain
separable from, or merely link (or bind by name) to the interfaces of,
the Work and Derivative Works thereof.
"Contribution" shall mean any work of authorship, including
the original version of the Work and any modifications or additions
to that Work or Derivative Works thereof, that is intentionally
submitted to Licensor for inclusion in the Work by the copyright owner
or by an individual or Legal Entity authorized to submit on behalf of
the copyright owner. For the purposes of this definition, "submitted"
means any form of electronic, verbal, or written communication sent
to the Licensor or its representatives, including but not limited to
communication on electronic mailing lists, source code control systems,
and issue tracking systems that are managed by, or on behalf of, the
Licensor for the purpose of discussing and improving the Work, but
excluding communication that is conspicuously marked or otherwise
designated in writing by the copyright owner as "Not a Contribution."
"Contributor" shall mean Licensor and any individual or Legal Entity
on behalf of whom a Contribution has been received by Licensor and
subsequently incorporated within the Work.
2. Grant of Copyright License. Subject to the terms and conditions of
this License, each Contributor hereby grants to You a perpetual,
worldwide, non-exclusive, no-charge, royalty-free, irrevocable
copyright license to reproduce, prepare Derivative Works of,
publicly display, publicly perform, sublicense, and distribute the
Work and such Derivative Works in Source or Object form.
3. Grant of Patent License. Subject to the terms and conditions of
this License, each Contributor hereby grants to You a perpetual,
worldwide, non-exclusive, no-charge, royalty-free, irrevocable
(except as stated in this section) patent license to make, have made,
use, offer to sell, sell, import, and otherwise transfer the Work,
where such license applies only to those patent claims licensable
by such Contributor that are necessarily infringed by their
Contribution(s) alone or by combination of their Contribution(s)
with the Work to which such Contribution(s) was submitted. If You
institute patent litigation against any entity (including a
cross-claim or counterclaim in a lawsuit) alleging that the Work
or a Contribution incorporated within the Work constitutes direct
or contributory patent infringement, then any patent licenses
granted to You under this License for that Work shall terminate
as of the date such litigation is filed.
4. Redistribution. You may reproduce and distribute copies of the
Work or Derivative Works thereof in any medium, with or without
modifications, and in Source or Object form, provided that You
meet the following conditions:
(a) You must give any other recipients of the Work or
Derivative Works a copy of this License; and
(b) You must cause any modified files to carry prominent notices
stating that You changed the files; and
(c) You must retain, in the Source form of any Derivative Works
that You distribute, all copyright, patent, trademark, and
attribution notices from the Source form of the Work,
excluding those notices that do not pertain to any part of
the Derivative Works; and
(d) If the Work includes a "NOTICE" text file as part of its
distribution, then any Derivative Works that You distribute must
include a readable copy of the attribution notices contained
within such NOTICE file, excluding those notices that do not
pertain to any part of the Derivative Works, in at least one
of the following places: within a NOTICE text file distributed
as part of the Derivative Works; within the Source form or
documentation, if provided along with the Derivative Works; or,
within a display generated by the Derivative Works, if and
wherever such third-party notices normally appear. The contents
of the NOTICE file are for informational purposes only and
do not modify the License. You may add Your own attribution
notices within Derivative Works that You distribute, alongside
or as an addendum to the NOTICE text from the Work, provided
that such additional attribution notices cannot be construed
as modifying the License.
You may add Your own copyright statement to Your modifications and
may provide additional or different license terms and conditions
for use, reproduction, or distribution of Your modifications, or
for any such Derivative Works as a whole, provided Your use,
reproduction, and distribution of the Work otherwise complies with
the conditions stated in this License.
5. Submission of Contributions. Unless You explicitly state otherwise,
any Contribution intentionally submitted for inclusion in the Work
by You to the Licensor shall be under the terms and conditions of
this License, without any additional terms or conditions.
Notwithstanding the above, nothing herein shall supersede or modify
the terms of any separate license agreement you may have executed
with Licensor regarding such Contributions.
6. Trademarks. This License does not grant permission to use the trade
names, trademarks, service marks, or product names of the Licensor,
except as required for reasonable and customary use in describing the
origin of the Work and reproducing the content of the NOTICE file.
7. Disclaimer of Warranty. Unless required by applicable law or
agreed to in writing, Licensor provides the Work (and each
Contributor provides its Contributions) on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
implied, including, without limitation, any warranties or conditions
of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A
PARTICULAR PURPOSE. You are solely responsible for determining the
appropriateness of using or redistributing the Work and assume any
risks associated with Your exercise of permissions under this License.
8. Limitation of Liability. In no event and under no legal theory,
whether in tort (including negligence), contract, or otherwise,
unless required by applicable law (such as deliberate and grossly
negligent acts) or agreed to in writing, shall any Contributor be
liable to You for damages, including any direct, indirect, special,
incidental, or consequential damages of any character arising as a
result of this License or out of the use or inability to use the
Work (including but not limited to damages for loss of goodwill,
work stoppage, computer failure or malfunction, or any and all
other commercial damages or losses), even if such Contributor
has been advised of the possibility of such damages.
9. Accepting Warranty or Additional Liability. While redistributing
the Work or Derivative Works thereof, You may choose to offer,
and charge a fee for, acceptance of support, warranty, indemnity,
or other liability obligations and/or rights consistent with this
License. However, in accepting such obligations, You may act only
on Your own behalf and on Your sole responsibility, not on behalf
of any other Contributor, and only if You agree to indemnify,
defend, and hold each Contributor harmless for any liability
incurred by, or claims asserted against, such Contributor by reason
of your accepting any such warranty or additional liability.
END OF TERMS AND CONDITIONS
APPENDIX: How to apply the Apache License to your work.
To apply the Apache License to your work, attach the following
boilerplate notice, with the fields enclosed by brackets "[]"
replaced with your own identifying information. (Don't include
the brackets!) The text should be enclosed in the appropriate
comment syntax for the file format. We also recommend that a
file or class name and description of purpose be included on the
same "printed page" as the copyright notice for easier
identification within third-party archives.
Copyright [yyyy] [name of copyright owner]
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.

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# Pingora
[![License](https://img.shields.io/badge/License-Apache_2.0-blue.svg)](https://opensource.org/licenses/Apache-2.0)
A library for building fast, reliable and evolvable network services.

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[package]
name = "pingora-limits"
version = "0.1.0"
authors = ["Yuchen Wu <yuchen@cloudflare.com>"]
license = "Apache-2.0"
description = "A library for rate limiting and event frequency estimation"
edition = "2018"
[lib]
name = "pingora_limits"
path = "src/lib.rs"
[dependencies]
ahash = "0"
[dev-dependencies]
rand = "0"
dashmap = "5"
dhat = "0"
[[bench]]
name = "benchmark"
harness = false
[features]
dhat-heap = [] # for benchmark only

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Apache License
Version 2.0, January 2004
http://www.apache.org/licenses/
TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
1. Definitions.
"License" shall mean the terms and conditions for use, reproduction,
and distribution as defined by Sections 1 through 9 of this document.
"Licensor" shall mean the copyright owner or entity authorized by
the copyright owner that is granting the License.
"Legal Entity" shall mean the union of the acting entity and all
other entities that control, are controlled by, or are under common
control with that entity. For the purposes of this definition,
"control" means (i) the power, direct or indirect, to cause the
direction or management of such entity, whether by contract or
otherwise, or (ii) ownership of fifty percent (50%) or more of the
outstanding shares, or (iii) beneficial ownership of such entity.
"You" (or "Your") shall mean an individual or Legal Entity
exercising permissions granted by this License.
"Source" form shall mean the preferred form for making modifications,
including but not limited to software source code, documentation
source, and configuration files.
"Object" form shall mean any form resulting from mechanical
transformation or translation of a Source form, including but
not limited to compiled object code, generated documentation,
and conversions to other media types.
"Work" shall mean the work of authorship, whether in Source or
Object form, made available under the License, as indicated by a
copyright notice that is included in or attached to the work
(an example is provided in the Appendix below).
"Derivative Works" shall mean any work, whether in Source or Object
form, that is based on (or derived from) the Work and for which the
editorial revisions, annotations, elaborations, or other modifications
represent, as a whole, an original work of authorship. For the purposes
of this License, Derivative Works shall not include works that remain
separable from, or merely link (or bind by name) to the interfaces of,
the Work and Derivative Works thereof.
"Contribution" shall mean any work of authorship, including
the original version of the Work and any modifications or additions
to that Work or Derivative Works thereof, that is intentionally
submitted to Licensor for inclusion in the Work by the copyright owner
or by an individual or Legal Entity authorized to submit on behalf of
the copyright owner. For the purposes of this definition, "submitted"
means any form of electronic, verbal, or written communication sent
to the Licensor or its representatives, including but not limited to
communication on electronic mailing lists, source code control systems,
and issue tracking systems that are managed by, or on behalf of, the
Licensor for the purpose of discussing and improving the Work, but
excluding communication that is conspicuously marked or otherwise
designated in writing by the copyright owner as "Not a Contribution."
"Contributor" shall mean Licensor and any individual or Legal Entity
on behalf of whom a Contribution has been received by Licensor and
subsequently incorporated within the Work.
2. Grant of Copyright License. Subject to the terms and conditions of
this License, each Contributor hereby grants to You a perpetual,
worldwide, non-exclusive, no-charge, royalty-free, irrevocable
copyright license to reproduce, prepare Derivative Works of,
publicly display, publicly perform, sublicense, and distribute the
Work and such Derivative Works in Source or Object form.
3. Grant of Patent License. Subject to the terms and conditions of
this License, each Contributor hereby grants to You a perpetual,
worldwide, non-exclusive, no-charge, royalty-free, irrevocable
(except as stated in this section) patent license to make, have made,
use, offer to sell, sell, import, and otherwise transfer the Work,
where such license applies only to those patent claims licensable
by such Contributor that are necessarily infringed by their
Contribution(s) alone or by combination of their Contribution(s)
with the Work to which such Contribution(s) was submitted. If You
institute patent litigation against any entity (including a
cross-claim or counterclaim in a lawsuit) alleging that the Work
or a Contribution incorporated within the Work constitutes direct
or contributory patent infringement, then any patent licenses
granted to You under this License for that Work shall terminate
as of the date such litigation is filed.
4. Redistribution. You may reproduce and distribute copies of the
Work or Derivative Works thereof in any medium, with or without
modifications, and in Source or Object form, provided that You
meet the following conditions:
(a) You must give any other recipients of the Work or
Derivative Works a copy of this License; and
(b) You must cause any modified files to carry prominent notices
stating that You changed the files; and
(c) You must retain, in the Source form of any Derivative Works
that You distribute, all copyright, patent, trademark, and
attribution notices from the Source form of the Work,
excluding those notices that do not pertain to any part of
the Derivative Works; and
(d) If the Work includes a "NOTICE" text file as part of its
distribution, then any Derivative Works that You distribute must
include a readable copy of the attribution notices contained
within such NOTICE file, excluding those notices that do not
pertain to any part of the Derivative Works, in at least one
of the following places: within a NOTICE text file distributed
as part of the Derivative Works; within the Source form or
documentation, if provided along with the Derivative Works; or,
within a display generated by the Derivative Works, if and
wherever such third-party notices normally appear. The contents
of the NOTICE file are for informational purposes only and
do not modify the License. You may add Your own attribution
notices within Derivative Works that You distribute, alongside
or as an addendum to the NOTICE text from the Work, provided
that such additional attribution notices cannot be construed
as modifying the License.
You may add Your own copyright statement to Your modifications and
may provide additional or different license terms and conditions
for use, reproduction, or distribution of Your modifications, or
for any such Derivative Works as a whole, provided Your use,
reproduction, and distribution of the Work otherwise complies with
the conditions stated in this License.
5. Submission of Contributions. Unless You explicitly state otherwise,
any Contribution intentionally submitted for inclusion in the Work
by You to the Licensor shall be under the terms and conditions of
this License, without any additional terms or conditions.
Notwithstanding the above, nothing herein shall supersede or modify
the terms of any separate license agreement you may have executed
with Licensor regarding such Contributions.
6. Trademarks. This License does not grant permission to use the trade
names, trademarks, service marks, or product names of the Licensor,
except as required for reasonable and customary use in describing the
origin of the Work and reproducing the content of the NOTICE file.
7. Disclaimer of Warranty. Unless required by applicable law or
agreed to in writing, Licensor provides the Work (and each
Contributor provides its Contributions) on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
implied, including, without limitation, any warranties or conditions
of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A
PARTICULAR PURPOSE. You are solely responsible for determining the
appropriateness of using or redistributing the Work and assume any
risks associated with Your exercise of permissions under this License.
8. Limitation of Liability. In no event and under no legal theory,
whether in tort (including negligence), contract, or otherwise,
unless required by applicable law (such as deliberate and grossly
negligent acts) or agreed to in writing, shall any Contributor be
liable to You for damages, including any direct, indirect, special,
incidental, or consequential damages of any character arising as a
result of this License or out of the use or inability to use the
Work (including but not limited to damages for loss of goodwill,
work stoppage, computer failure or malfunction, or any and all
other commercial damages or losses), even if such Contributor
has been advised of the possibility of such damages.
9. Accepting Warranty or Additional Liability. While redistributing
the Work or Derivative Works thereof, You may choose to offer,
and charge a fee for, acceptance of support, warranty, indemnity,
or other liability obligations and/or rights consistent with this
License. However, in accepting such obligations, You may act only
on Your own behalf and on Your sole responsibility, not on behalf
of any other Contributor, and only if You agree to indemnify,
defend, and hold each Contributor harmless for any liability
incurred by, or claims asserted against, such Contributor by reason
of your accepting any such warranty or additional liability.
END OF TERMS AND CONDITIONS
APPENDIX: How to apply the Apache License to your work.
To apply the Apache License to your work, attach the following
boilerplate notice, with the fields enclosed by brackets "[]"
replaced with your own identifying information. (Don't include
the brackets!) The text should be enclosed in the appropriate
comment syntax for the file format. We also recommend that a
file or class name and description of purpose be included on the
same "printed page" as the copyright notice for easier
identification within third-party archives.
Copyright [yyyy] [name of copyright owner]
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.

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// Copyright 2023 Cloudflare, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#[cfg(feature = "dhat-heap")]
#[global_allocator]
static ALLOC: dhat::Alloc = dhat::Alloc;
use ahash::RandomState;
use dashmap::DashMap;
use pingora_limits::estimator::Estimator;
use rand::distributions::Uniform;
use rand::{thread_rng, Rng};
use std::collections::HashMap;
use std::sync::atomic::{AtomicUsize, Ordering};
use std::sync::Arc;
use std::sync::Mutex;
use std::thread;
use std::time::Instant;
trait Counter {
fn incr(&self, key: u32, value: usize);
fn name() -> &'static str;
}
#[derive(Default)]
struct NaiveCounter(Mutex<HashMap<u32, usize>>);
impl Counter for NaiveCounter {
fn incr(&self, key: u32, value: usize) {
let mut map = self.0.lock().unwrap();
if let Some(v) = map.get_mut(&key) {
*v += value;
} else {
map.insert(key, value);
}
}
fn name() -> &'static str {
"Naive Counter"
}
}
#[derive(Default)]
struct OptimizedCounter(DashMap<u32, AtomicUsize, RandomState>);
impl Counter for OptimizedCounter {
fn incr(&self, key: u32, value: usize) {
if let Some(v) = self.0.get(&key) {
v.fetch_add(value, Ordering::Relaxed);
return;
}
self.0.insert(key, AtomicUsize::new(value));
}
fn name() -> &'static str {
"Optimized Counter"
}
}
impl Counter for Estimator {
fn incr(&self, key: u32, value: usize) {
self.incr(key, value as isize);
}
fn name() -> &'static str {
"Pingora Estimator"
}
}
fn run_bench<T: Counter>(
counter: &T,
samples: usize,
distribution: &Uniform<u32>,
test_name: &str,
) {
let mut rng = thread_rng();
let before = Instant::now();
for _ in 0..samples {
let event: u32 = rng.sample(distribution);
counter.incr(event, 1);
}
let elapsed = before.elapsed();
println!(
"{} {test_name} {:?} total, {:?} avg per operation",
T::name(),
elapsed,
elapsed / samples as u32
);
}
fn run_threaded_bench<T: Counter + Send + Sync + 'static>(
threads: usize,
counter: Arc<T>,
samples: usize,
distribution: &Uniform<u32>,
) {
let mut handlers = vec![];
for i in 0..threads {
let est = counter.clone();
let dist = *distribution;
let handler = thread::spawn(move || {
run_bench(est.as_ref(), samples, &dist, &format!("thread#{i}"));
});
handlers.push(handler);
}
for thread in handlers {
thread.join().unwrap();
}
}
/*
Pingora Estimator single thread 1.042849543s total, 10ns avg per operation
Naive Counter single thread 5.12641496s total, 51ns avg per operation
Optimized Counter single thread 4.302553352s total, 43ns avg per operation
Pingora Estimator thread#7 2.654667606s total, 212ns avg per operation
Pingora Estimator thread#2 2.65651993s total, 212ns avg per operation
Pingora Estimator thread#4 2.658225266s total, 212ns avg per operation
Pingora Estimator thread#0 2.660603361s total, 212ns avg per operation
Pingora Estimator thread#1 2.66139014s total, 212ns avg per operation
Pingora Estimator thread#6 2.663498849s total, 213ns avg per operation
Pingora Estimator thread#5 2.663344276s total, 213ns avg per operation
Pingora Estimator thread#3 2.664652951s total, 213ns avg per operation
Naive Counter thread#7 18.795881242s total, 1.503µs avg per operation
Naive Counter thread#1 18.805652672s total, 1.504µs avg per operation
Naive Counter thread#6 18.818084416s total, 1.505µs avg per operation
Naive Counter thread#4 18.832778982s total, 1.506µs avg per operation
Naive Counter thread#3 18.833952715s total, 1.506µs avg per operation
Naive Counter thread#2 18.837975133s total, 1.507µs avg per operation
Naive Counter thread#0 18.8397464s total, 1.507µs avg per operation
Naive Counter thread#5 18.842616299s total, 1.507µs avg per operation
Optimized Counter thread#4 2.650860314s total, 212ns avg per operation
Optimized Counter thread#0 2.651867013s total, 212ns avg per operation
Optimized Counter thread#2 2.656473381s total, 212ns avg per operation
Optimized Counter thread#5 2.657715876s total, 212ns avg per operation
Optimized Counter thread#1 2.658275111s total, 212ns avg per operation
Optimized Counter thread#7 2.658770751s total, 212ns avg per operation
Optimized Counter thread#6 2.659831251s total, 212ns avg per operation
Optimized Counter thread#3 2.664375398s total, 213ns avg per operation
*/
/* cargo bench --features dhat-heap for memory info
Pingora Estimator single thread 1.066846098s total, 10ns avg per operation
dhat: Total: 26,184 bytes in 9 blocks
dhat: At t-gmax: 26,184 bytes in 9 blocks
dhat: At t-end: 1,464 bytes in 5 blocks
dhat: The data has been saved to dhat-heap.json, and is viewable with dhat/dh_view.html
Naive Counter single thread 5.429089242s total, 54ns avg per operation
dhat: Total: 71,303,260 bytes in 20 blocks
dhat: At t-gmax: 53,477,392 bytes in 2 blocks
dhat: At t-end: 0 bytes in 0 blocks
dhat: The data has been saved to dhat-heap.json, and is viewable with dhat/dh_view.html
Optimized Counter single thread 4.361720355s total, 43ns avg per operation
dhat: Total: 71,307,722 bytes in 491 blocks
dhat: At t-gmax: 36,211,208 bytes in 34 blocks
dhat: At t-end: 0 bytes in 0 blocks
dhat: The data has been saved to dhat-heap.json, and is viewable with dhat/dh_view.html
*/
fn main() {
const SAMPLES: usize = 100_000_000;
const THREADS: usize = 8;
const ITEMS: u32 = 1_000_000;
const SAMPLES_PER_THREAD: usize = SAMPLES / THREADS;
let distribution = Uniform::new(0, ITEMS);
// single thread
{
#[cfg(feature = "dhat-heap")]
let _profiler = dhat::Profiler::new_heap();
let pingora_est = Estimator::new(3, 1024);
run_bench(&pingora_est, SAMPLES, &distribution, "single thread");
}
{
#[cfg(feature = "dhat-heap")]
let _profiler = dhat::Profiler::new_heap();
let naive: NaiveCounter = Default::default();
run_bench(&naive, SAMPLES, &distribution, "single thread");
}
{
#[cfg(feature = "dhat-heap")]
let _profiler = dhat::Profiler::new_heap();
let optimized: OptimizedCounter = Default::default();
run_bench(&optimized, SAMPLES, &distribution, "single thread");
}
// multithread
let pingora_est = Arc::new(Estimator::new(3, 1024));
run_threaded_bench(THREADS, pingora_est, SAMPLES_PER_THREAD, &distribution);
let naive: Arc<NaiveCounter> = Default::default();
run_threaded_bench(THREADS, naive, SAMPLES_PER_THREAD, &distribution);
let optimized: Arc<OptimizedCounter> = Default::default();
run_threaded_bench(THREADS, optimized, SAMPLES_PER_THREAD, &distribution);
}

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// Copyright 2023 Cloudflare, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//! The estimator module contains a Count-Min Sketch type to help estimate the frequency of an item.
use crate::hash;
use crate::RandomState;
use std::hash::Hash;
use std::sync::atomic::{AtomicIsize, Ordering};
/// An implementation of a lock-free count–min sketch estimator. See the [wikipedia] page for more
/// information.
///
/// [wikipedia]: https://en.wikipedia.org/wiki/Count%E2%80%93min_sketch
pub struct Estimator {
estimator: Box<[(Box<[AtomicIsize]>, RandomState)]>,
}
impl Estimator {
/// Create a new `Estimator` with the given amount of hashes and columns (slots).
pub fn new(hashes: usize, slots: usize) -> Self {
let mut estimator = Vec::with_capacity(hashes);
for _ in 0..hashes {
let mut slot = Vec::with_capacity(slots);
for _ in 0..slots {
slot.push(AtomicIsize::new(0));
}
estimator.push((slot.into_boxed_slice(), RandomState::new()));
}
Estimator {
estimator: estimator.into_boxed_slice(),
}
}
/// Increment `key` by the value given. Return the new estimated value as a result.
/// Note: overflow can happen. When some of the internal counters overflow, a negative number
/// will be returned. It is up to the caller to catch and handle this case.
pub fn incr<T: Hash>(&self, key: T, value: isize) -> isize {
let mut min = isize::MAX;
for (slot, hasher) in self.estimator.iter() {
let hash = hash(&key, hasher) as usize;
let counter = &slot[hash % slot.len()];
// Overflow is allowed for simplicity
let current = counter.fetch_add(value, Ordering::Relaxed);
min = std::cmp::min(min, current + value);
}
min
}
/// Decrement `key` by the value given.
pub fn decr<T: Hash>(&self, key: T, value: isize) {
for (slot, hasher) in self.estimator.iter() {
let hash = hash(&key, hasher) as usize;
let counter = &slot[hash % slot.len()];
counter.fetch_sub(value, Ordering::Relaxed);
}
}
/// Get the estimated frequency of `key`.
pub fn get<T: Hash>(&self, key: T) -> isize {
let mut min = isize::MAX;
for (slot, hasher) in self.estimator.iter() {
let hash = hash(&key, hasher) as usize;
let counter = &slot[hash % slot.len()];
let current = counter.load(Ordering::Relaxed);
min = std::cmp::min(min, current);
}
min
}
/// Reset all values inside this `Estimator`.
pub fn reset(&self) {
for (slot, _) in self.estimator.iter() {
for counter in slot.iter() {
counter.store(0, Ordering::Relaxed);
}
}
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn incr() {
let est = Estimator::new(8, 8);
let v = est.incr("a", 1);
assert_eq!(v, 1);
let v = est.incr("b", 1);
assert_eq!(v, 1);
let v = est.incr("a", 2);
assert_eq!(v, 3);
let v = est.incr("b", 2);
assert_eq!(v, 3);
}
#[test]
fn desc() {
let est = Estimator::new(8, 8);
est.incr("a", 3);
est.incr("b", 3);
est.decr("a", 1);
est.decr("b", 1);
assert_eq!(est.get("a"), 2);
assert_eq!(est.get("b"), 2);
}
#[test]
fn get() {
let est = Estimator::new(8, 8);
est.incr("a", 1);
est.incr("a", 2);
est.incr("b", 1);
est.incr("b", 2);
assert_eq!(est.get("a"), 3);
assert_eq!(est.get("b"), 3);
}
}

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// Copyright 2023 Cloudflare, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//! The inflight module defines the [Inflight] type which estimates the count of events occurring
//! at any point in time.
use crate::estimator::Estimator;
use crate::{hash, RandomState};
use std::hash::Hash;
use std::sync::Arc;
/// An `Inflight` type tracks the frequency of actions that are actively occurring. When the value
/// is dropped from scope, the count will automatically decrease.
pub struct Inflight {
estimator: Arc<Estimator>,
hasher: RandomState,
}
// fixed parameters for simplicity: hashes: h, slots: n
// Time complexity for a lookup operation is O(h). Space complexity is O(h*n)
// False positive ratio is 1/(n^h)
// We choose a small h and a large n to keep lookup cheap and FP ratio low
const HASHES: usize = 4;
const SLOTS: usize = 8192;
impl Inflight {
/// Create a new `Inflight`.
pub fn new() -> Self {
Inflight {
estimator: Arc::new(Estimator::new(HASHES, SLOTS)),
hasher: RandomState::new(),
}
}
/// Increment `key` by the value given. The return value is a tuple of a [Guard] and the
/// estimated count.
pub fn incr<T: Hash>(&self, key: T, value: isize) -> (Guard, isize) {
let guard = Guard {
estimator: self.estimator.clone(),
id: hash(key, &self.hasher),
value,
};
let estimation = guard.incr();
(guard, estimation)
}
}
/// A `Guard` is returned when an `Inflight` key is incremented via [Inflight::incr].
pub struct Guard {
estimator: Arc<Estimator>,
// store the hash instead of the actual key to save space
id: u64,
value: isize,
}
impl Guard {
/// Increment the key's value that the `Guard` was created from.
pub fn incr(&self) -> isize {
self.estimator.incr(self.id, self.value)
}
/// Get the estimated count of the key that the `Guard` was created from.
pub fn get(&self) -> isize {
self.estimator.get(self.id)
}
}
impl Drop for Guard {
fn drop(&mut self) {
self.estimator.decr(self.id, self.value)
}
}
impl std::fmt::Debug for Guard {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
f.debug_struct("Guard")
.field("id", &self.id)
.field("value", &self.value)
// no need to dump shared estimator
.finish()
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn inflight_count() {
let inflight = Inflight::new();
let (g1, v) = inflight.incr("a", 1);
assert_eq!(v, 1);
let (g2, v) = inflight.incr("a", 2);
assert_eq!(v, 3);
drop(g1);
assert_eq!(g2.get(), 2);
drop(g2);
let (_, v) = inflight.incr("a", 1);
assert_eq!(v, 1);
}
}

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// Copyright 2023 Cloudflare, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//! The pingora_limits crate contains modules that can help introduce things like rate limiting or
//! thread-safe event count estimation.
#![warn(clippy::all)]
#![allow(clippy::new_without_default)]
#![allow(clippy::type_complexity)]
pub mod estimator;
pub mod inflight;
pub mod rate;
use ahash::RandomState;
use std::hash::{BuildHasher, Hash, Hasher};
#[inline]
fn hash<T: Hash>(key: T, hasher: &RandomState) -> u64 {
let mut hasher = hasher.build_hasher();
key.hash(&mut hasher);
hasher.finish()
}

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// Copyright 2023 Cloudflare, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//! The rate module defines the [Rate] type that helps estimate the occurrence of events over a
//! period of time.
use crate::estimator::Estimator;
use std::hash::Hash;
use std::sync::atomic::{AtomicBool, AtomicU64, Ordering};
use std::time::Instant;
/// A stable rate estimator that reports the rate of events in the past `interval` time.
/// It returns the average rate between `interval` * 2 and `interval` while collecting the events
/// happening between `interval` and now.
///
/// This estimator ignores events that happen less than once per `interval` time.
pub struct Rate {
// 2 slots so that we use one to collect the current events and the other to report rate
red_slot: Estimator,
blue_slot: Estimator,
red_or_blue: AtomicBool, // true: current slot is red, otherwise blue
start: Instant,
// Use u64 below instead of Instant because we want atomic operation
reset_interval_ms: u64, // the time interval to reset `current` and move it to `previous`
last_reset_time: AtomicU64, // the timestamp in ms since `start`
}
// see inflight module for the meaning for these numbers
const HASHES: usize = 4;
const SLOTS: usize = 1024; // This value can be lower if interval is short (key cardinality is low)
impl Rate {
/// Create a new `Rate` with the given interval.
pub fn new(interval: std::time::Duration) -> Self {
Rate {
red_slot: Estimator::new(HASHES, SLOTS),
blue_slot: Estimator::new(HASHES, SLOTS),
red_or_blue: AtomicBool::new(true),
start: Instant::now(),
reset_interval_ms: interval.as_millis() as u64, // should be small not to overflow
last_reset_time: AtomicU64::new(0),
}
}
fn current(&self, red_or_blue: bool) -> &Estimator {
if red_or_blue {
&self.red_slot
} else {
&self.blue_slot
}
}
fn previous(&self, red_or_blue: bool) -> &Estimator {
if red_or_blue {
&self.blue_slot
} else {
&self.red_slot
}
}
fn red_or_blue(&self) -> bool {
self.red_or_blue.load(Ordering::SeqCst)
}
/// Return the per second rate estimation.
pub fn rate<T: Hash>(&self, key: &T) -> f64 {
let past_ms = self.maybe_reset();
if past_ms >= self.reset_interval_ms * 2 {
// already missed 2 intervals, no data, just report 0 as a short cut
return 0f64;
}
self.previous(self.red_or_blue()).get(key) as f64 / self.reset_interval_ms as f64 * 1000.0
}
/// Report new events and return number of events seen so far in the current interval.
pub fn observe<T: Hash>(&self, key: &T, events: isize) -> isize {
self.maybe_reset();
self.current(self.red_or_blue()).incr(key, events)
}
// reset if needed, return the time since last reset for other fn to use
fn maybe_reset(&self) -> u64 {
// should be short enough not to overflow
let now = Instant::now().duration_since(self.start).as_millis() as u64;
let last_reset = self.last_reset_time.load(Ordering::SeqCst);
let past_ms = now - last_reset;
if past_ms < self.reset_interval_ms {
// no need to reset
return past_ms;
}
let red_or_blue = self.red_or_blue();
match self.last_reset_time.compare_exchange(
last_reset,
now,
Ordering::SeqCst,
Ordering::Acquire,
) {
Ok(_) => {
// first clear the previous slot
self.previous(red_or_blue).reset();
// then flip the flag to tell others to use the reset slot
self.red_or_blue.store(!red_or_blue, Ordering::SeqCst);
// if current time is beyond 2 intervals, the data stored in the previous slot
// is also stale, we should clear that too
if now - last_reset >= self.reset_interval_ms * 2 {
// Note that this is the previous one now because we just flipped self.red_or_blue
self.current(red_or_blue).reset();
}
}
Err(new) => {
// another thread beats us to it
assert!(new >= now - 1000); // double check that the new timestamp looks right
}
}
past_ms
}
}
#[cfg(test)]
mod tests {
use super::*;
use std::thread::sleep;
use std::time::Duration;
#[test]
fn test_observe_rate() {
let r = Rate::new(Duration::from_secs(1));
let key = 1;
// second: 0
let observed = r.observe(&key, 3);
assert_eq!(observed, 3);
let observed = r.observe(&key, 2);
assert_eq!(observed, 5);
assert_eq!(r.rate(&key), 0f64); // no estimation yet because the interval has not passed
// second: 1
sleep(Duration::from_secs(1));
let observed = r.observe(&key, 4);
assert_eq!(observed, 4);
assert_eq!(r.rate(&key), 5f64); // 5 rps
// second: 2
sleep(Duration::from_secs(1));
assert_eq!(r.rate(&key), 4f64);
// second: 3
sleep(Duration::from_secs(1));
assert_eq!(r.rate(&key), 0f64); // no event observed in the past 2 second
}
}