RateLimitHeaders

A .NET library for parsing IETF RateLimit headers and enabling proactive rate limit awareness in HTTP clients.

Get Started API Reference GitHub

Packages

RateLimitHeaders

Core library with IETF RateLimit header parsing and IHttpClientFactory DelegatingHandler for proactive throttling.

dotnet add package RateLimitHeaders

RateLimitHeaders.Polly

Polly v8 integration for adding rate limit awareness to resilience pipelines.

dotnet add package RateLimitHeaders.Polly

Quick Start

// Using with IHttpClientFactory and Microsoft.Extensions.Http.Resilience
services.AddHttpClient("MyApi")
    .AddRateLimitAwareHandler(options =>
    {
        options.EnableProactiveThrottling = true;
        options.QuotaLowThreshold = 0.1; // Warn at 10% remaining
    })
    .AddStandardResilienceHandler(); // Microsoft resilience (retry, circuit breaker, etc.)

// Or using with Polly resilience pipelines directly
var pipeline = new ResiliencePipelineBuilder<HttpResponseMessage>()
    .AddRateLimitHeaders(options => options.EnableProactiveThrottling = true)
    .AddRetry(new RetryStrategyOptions<HttpResponseMessage>())
    .Build();

Features

IETF Standard Parsing

Parses RateLimit and RateLimit-Policy headers per draft-ietf-httpapi-ratelimit-headers-10. Extracts remaining quota, reset time, window size, and partition keys.

Proactive Throttling

Automatically delays requests when quota is low, preventing 429 errors before they happen. Configurable thresholds, delays, and custom throttling algorithms.

Polly Integration

Works seamlessly with Polly v8 resilience pipelines. Add rate limit awareness alongside retry, circuit breaker, and timeout strategies.

DelegatingHandler

Drop-in handler for IHttpClientFactory. Easy integration with ASP.NET Core dependency injection and named/typed HttpClients.

Extensible Throttling

Implement IThrottlingAlgorithm for custom strategies. Built-in percentage-based algorithm with configurable threshold, factor, and max delay.

Observable Events

Callbacks for rate limit info, quota warnings, and throttling events. Perfect for logging, metrics, and alerting when approaching limits.

Supported Frameworks

Package	.NET 8	.NET 9	.NET 10
RateLimitHeaders	✅	✅	✅
RateLimitHeaders.Polly	✅	✅	✅

Contributing

We welcome contributions! Whether it's bug reports, feature requests, documentation improvements, or code contributions.

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