PollyRateLimiter 1.0.2

PollyRateLimiter

Convenience extension methods for Polly v8 resilience pipelines.

Polly v8 ships with AddConcurrencyLimiter out of the box, but leaves FixedWindow, SlidingWindow, and TokenBucket as bring-your-own. This package fills that gap with one-liner extension methods for all three strategies on top of System.Threading.RateLimiting.

Install

dotnet add package PollyRateLimiter

Usage

using PollyRateLimiter;

// Fixed window: 100 requests per second
var pipeline = new ResiliencePipelineBuilder()
    .AddFixedWindowRateLimiter(permitLimit: 100, window: TimeSpan.FromSeconds(1))
    .Build();

// Sliding window: 100 requests per second, smoothed into 4 segments
var pipeline = new ResiliencePipelineBuilder()
    .AddSlidingWindowRateLimiter(permitLimit: 100, window: TimeSpan.FromSeconds(1), segmentsPerWindow: 4)
    .Build();

// Token bucket: burst up to 200, replenish 50 per second
var pipeline = new ResiliencePipelineBuilder()
    .AddTokenBucketRateLimiter(tokenLimit: 200, tokensPerPeriod: 50, replenishmentPeriod: TimeSpan.FromSeconds(1))
    .Build();

Queue limit

By default, executions that exceed the limit are rejected immediately (queueLimit: 0). Pass a positive value to queue them instead:

var pipeline = new ResiliencePipelineBuilder()
    .AddFixedWindowRateLimiter(permitLimit: 10, window: TimeSpan.FromSeconds(1), queueLimit: 5)
    .Build();

OnRejected callback

Use the optional configure callback to attach an OnRejected handler or change other RateLimiterStrategyOptions:

var pipeline = new ResiliencePipelineBuilder()
    .AddTokenBucketRateLimiter(
        tokenLimit: 100,
        tokensPerPeriod: 20,
        replenishmentPeriod: TimeSpan.FromSeconds(1),
        configure: opts => opts.OnRejected = args =>
        {
            logger.LogWarning("Rate limit exceeded. RetryAfter: {RetryAfter}", args.Lease.TryGetMetadata(MetadataName.RetryAfter, out var retry) ? retry : TimeSpan.Zero);
            return ValueTask.CompletedTask;
        })
    .Build();

Generic builder

All methods work with ResiliencePipelineBuilder<T> too:

var pipeline = new ResiliencePipelineBuilder<HttpResponseMessage>()
    .AddFixedWindowRateLimiter(permitLimit: 50, window: TimeSpan.FromSeconds(1))
    .AddRetry(new RetryStrategyOptions<HttpResponseMessage>())
    .Build();

Comparison with Polly built-ins

License

MIT