Crate aerorate 

AeroRate

aerorate is an ultra-fast, lock-free rate limiter implementing the Generic Cell Rate Algorithm (GCRA).

Designed for high-frequency trading gateways, reverse proxies, and high-throughput microservices.

Key Architecture Highlights

• Sub-10 Nanosecond Evaluation: Evaluates requests via a lock-free atomic CAS loop on a single AtomicU64 timestamp.
• Zero Memory Allocations: Hot path checks require zero heap allocations.
• Keyed Multi-Tenant Limiting: Sharded across power-of-two, cache-line padded partitions (#[repr(align(64))]) to eliminate false sharing.
• Borrowed Key Queries: Query with &str on String keys without cloning.
• Rich HTTP Telemetry: Yields retry_after, remaining_burst, and reset_after for standard HTTP headers.
• 100% Safe Rust: #![forbid(unsafe_code)] strictly enforced.

Quick Start

use aerorate::{RateLimiter, Quota};
use std::time::Duration;

// Allow 100 requests per second with burst allowance up to 20
let limiter = RateLimiter::new(Quota::per_second(100).allow_burst(20));

match limiter.check() {
    outcome if outcome.is_allowed() => {
        println!("Allowed! Remaining burst: {}", outcome.remaining_burst());
    }
    outcome => {
        println!("Throttled! Retry after: {:?}", outcome.retry_after());
    }
}

Multi-Tenant / Per-Key Rate Limiting

use aerorate::{KeyedRateLimiter, Quota};

// Rate limit per IP address or API key
let limiter: KeyedRateLimiter<String> = KeyedRateLimiter::per_second(10);

// Zero-allocation lookup using borrowed &str
let client_ip = "192.168.1.100";
if limiter.check(client_ip).is_allowed() {
    println!("Request accepted for {}", client_ip);
}

Re-exports

pub use keyed::KeyedRateLimiter;

pub use limiter::RateLimiter;

pub use metrics::RateMetrics;

pub use outcome::RateLimitResult;

pub use quota::Quota;

Modules

keyed

Keyed multi-tenant rate limiter with cache-line padded sharding.

limiter

Single-target lock-free rate limiter.

metrics

Telemetry metrics and snapshot tracking.

outcome

Rate limit evaluation outcomes and HTTP header helpers.

quota

Quota specifications and GCRA parameters.

state

Internal lock-free atomic GCRA state.

Type Aliases

StringRateLimiter

Type alias for a keyed rate limiter where keys are String.