Rate Limiter

A simple, in-memory sliding window rate limiter for Rust applications.

Features

• Sliding window algorithm for accurate rate limiting
• Per-key rate limiting (e.g., per API key or user)
• In-memory cache with automatic expiration
• Allow-list support for exempted keys
• Asynchronous, suitable for use in async web frameworks

Usage

Add the crate to your dependencies.

Example usage:

use ratelimiter::RateLimiter;

#[tokio::main]
async fn main() {
    // Create a rate limiter (allow-list is optional)
    let limiter = RateLimiter::new(vec![]).await;

    let api_key = "user123";
    // Allow up to 10 requests per 60 seconds (60000 ms)
    let response = limiter.allow(api_key, 60_000, 10.0).await;

    if response.allow {
        // Proceed with request
    } else {
        // Rate limit exceeded, check response.headers.retry_after
    }
}

API

• RateLimiter::new(allow_list: Vec<String>) -> RateLimiter - Create a new rate limiter.
• allow(&self, key: &str, window_size_ms: i64, max_requests: f64) -> RateLimitResponse - Check if a request for the given key is allowed.
• add_to_allow_list(&self, key: String) - Exempt a key from rate limiting.

License

MIT