1 unstable release
0.1.1 | Apr 26, 2022 |
---|---|
0.1.0 |
|
#4 in #governor
39 downloads per month
Used in dns-server
13KB
106 lines
prob-rate-limiter
ProbRateLimiter
is a probabilistic rate limiter.
When load approaches the configured limit,
the struct chooses randomly whether to accept or reject each request.
It adjusts the probability of rejection so throughput is steady around the limit.
Use Cases
- Shed load to prevent overload
- Avoid overloading the services you depend on
- Control costs
Features
- Tiny, uses 44 bytes
- 100% test coverage
- Optimized: 32ns per check, 31M checks per second on an i5-8259U
- No
unsafe
or unsafe deps
Limitations
- Requires a mutable reference.
- Not fair. Treats all requests equally, regardless of source. A client that overloads the server will consume most of the throughput.
Alternatives
- r8limit
- Uses a sliding window
- No
unsafe
or deps - Optimized: 48ns per check, 21M checks per second on an i5-8259U
- Requires a mutable reference.
- governor
- Uses a non-mutable reference, easy to share between threads
- Popular
- Good docs
- Optimized: 29ns per check on an i5-8259U.
- Unnecessary
unsafe
- Uses non-standard mutex library
parking_lot
- Uses a complicated algorithm
- leaky-bucket
- Async tasks can wait for their turn to use a resource.
- Unsuitable for load shedding because there is no
try_acquire
.
Related Crates
- safe-dns uses this
Example
let mut limiter = ProbRateLimiter::new(10.0).unwrap();
let mut now = Instant::now();
assert!(limiter.check(5, now));
assert!(limiter.check(5, now));
now += Duration::from_secs(1);
assert!(limiter.check(5, now));
assert!(limiter.check(5, now));
now += Duration::from_secs(1);
assert!(limiter.check(5, now));
assert!(limiter.check(5, now));
now += Duration::from_secs(1);
assert!(limiter.check(5, now));
assert!(limiter.check(5, now));
now += Duration::from_secs(1);
assert!(limiter.check(5, now));
assert!(limiter.check(5, now));
assert!(!limiter.check(5, now));
Cargo Geiger Safety Report
Metric output format: x/y
x = unsafe code used by the build
y = total unsafe code found in the crate
Symbols:
🔒 = No `unsafe` usage found, declares #![forbid(unsafe_code)]
❓ = No `unsafe` usage found, missing #![forbid(unsafe_code)]
☢️ = `unsafe` usage found
Functions Expressions Impls Traits Methods Dependency
0/0 0/0 0/0 0/0 0/0 🔒 prob-rate-limiter 0.1.1
0/0 0/0 0/0 0/0 0/0 🔒 └── oorandom 11.1.3
0/0 0/0 0/0 0/0 0/0
Changelog
- v0.1.1 - Simplify
new
. Add more docs. - v0.1.0 - Initial version
TO DO
- Publish
- Add graph from the benchmark.
License: Apache-2.0
Dependencies
~32KB