ratelimit

Token-bucket rate limiting for Go io.Reader / io.Writer, with per-key isolation and thread-safe controllers.

Quick start

package main

import (
	"io"
	"log"
	"strings"

	"github.com/lzle/ratelimit"
)

func main() {
	limiter, err := ratelimit.NewRateLimiter(map[string]ratelimit.RateLimitConfig{
		"user-a": {BandwidthQuota: 1024}, // bytes per second
	})
	if err != nil {
		log.Fatal(err)
	}

	key := "user-a"
	r := limiter.GetReader(key, strings.NewReader("hello ratelimit"))
	w := limiter.GetWriter(key, io.Discard)

	if _, err := io.Copy(w, r); err != nil {
		log.Fatal(err)
	}

	if err := limiter.Close(key); err != nil {
		log.Fatal(err)
	}
}

Notes

• Quota is bytes per second (BandwidthQuota).
• Each GetReader / GetWriter acquires the key — balance with Close(key) or references accumulate.
• Internals: token bucket, 50ms refill window, min burst 64 bytes per window.

Test

go test ./... -count=1

Acknowledgments

The flowctrl package is largely based on CubeFS util/flowctrl. See flowctrl/NOTICE for attribution and upstream licensing.

License

This repository is MIT licensed for the parts authored here (Copyright (c) 2026 lzle). Third-party code in flowctrl/ remains subject to the Apache License 2.0 of the CubeFS project; see flowctrl/NOTICE.