Crate throttle_my_fn

throttle_my_fn is a Rust attribute macro to limit a function’s number of runs over a specified period of time.

throttle_my_fn is a Rust attribute macro to limit a function’s number of runs over a specified period of time, even when called from multiple threads.

The primary use-case for this attribute macro is rate-limiting, e.g. to avoid hammering an online service or to avoid serving too many requests over a period of time.

The macro works by rewriting the function and prefixing it with the necessary book-keeping for throttling (see Usage below). The resulting function is thread-safe.

Usage

Add the dependency to your Cargo.toml:

[dependencies]
throttle_my_fn = "0.2"

Or, using cargo add:

$ cargo add throttle_my_fn

Include the macro:

use throttle_my_fn::throttle;

Annotate the functions you want to throttle:

#[throttle(10, Duration::from_secs(1))]
pub(crate) fn run_10_times_per_second(arg: &str) -> String {
  ...
}

#[throttle(1, Duration::from_millis(100))]
pub(crate) fn run_once_per_100_milliseconds(arg: &str) -> String {
  ...
}

Note that the function signatures are modified to wrap the return type in an Option, like so:

pub(crate) fn run_10_times_per_second(arg: &str) -> Option<String> {
  ...
}

pub(crate) fn run_once_per_100_milliseconds(arg: &str) -> Option<String> {
  ...
}

The Option<T> returned signifies whether the function executed or not.

Attribute Macros

throttle

Throttle a function’s execution count over a period of time.