Simple Go call/rate limiter

Oct 18, 2015
2 minutes read

I’ve written a call limiter (or rate limiter) for GoLang. It’s a very simple limiter, that enables you to limit the calls or a function.

You can setup the Package by giving the limit of concurrent jobs and the time between the jobs. This is especially useful for calling external APIs.


Think about an API that allows you to call it only 3 times every 2 minutes.

import (

func CallApiXYZ(i int) {
    // you call the API here, but we print something here

func main() {
    // create the limiter with 3 concurrent calls every 2 minutes
    limiter := NewReservoir(3, 2 * time.Minute)

    // Add 10 calls to the queue
    for i := 0; i < 5; i++ {
        limiter.add(CallApiXYZ, i)

    // Just to make sure that you know it's non-blocking
    fmt.Println("This is printed first")

    // Because it's non blocking, we have to wait for all 5 jobs and 1 more second
    // just to make sure the request are done in that time.
    time.Sleep((5 * 2 + 1) * time.Second)

More to come

There will be more in some time. It’s a good learning project of the Go concurrency patterns for me. So I will add some more features over time.Example Contributions are very welcome. I like to code in a team.

Links: - Reservoir on Github - Reservoir on GoDoc

Back to posts