go-ratelimiter

This is a negroni middleware that offers request rate limiting using token bucket approach.

It can apply a global rate limit or per key (where you can specify how to obtain the key from the request).

Additionally you can apply a different rate limit per key.

Getting Started

Global rate limiting

To add a global rate limit across all your request with a rate of 1 request per second.

m := NewGlobal().
        WithDefaultQuota(1, time.Second).
        Middleware()

n := negroni.Classic(m)
ts := httptest.NewServer(n)
defer ts.Close()

Changing status code

By default the status code 429 Too Many Requests will be returned when the specified rate limit is exceeded. In you want to change this behavior and return a different status code, just do:

m := NewGlobal().
        WithDefaultQuota(1, time.Second).
        WithStatusCode(400).
        Middleware()

In this case instead of the 429, a 400 Bad Request will be returned.

Rate limiting for different kind of request

Sometimes you want to apply a different rate for different kind of request. Lets take as an example that an account_id is being passed as a query parameter, and we want to apply the limit of 1 request per second but for each account individually instead of globally. In this case you can achieve it by doing:

getKey := func(req *http.Request) string {
    return req.URL.Query().Get("account_id")
}

m := NewLimitByKeys(getKey).
        WithDefaultQuota(1, time.Second).
        Middleware()
...

Different rate limits for different requests

Using the same example as previously, you can additionally specify a different rate limit for different accounts.

getKey := func(req *http.Request) string {
    return req.URL.Query().Get("account_id")
}
getQuota := func(key string) Quota {
    if key == "2" {
        return NewQuota(1, time.Minute)
    }
    return NewQuota(2, time.Second)
}

m := NewLimitByKeys(getKey).
        WithQuotaByKeys(getQuota).
        Middleware()
...

Headers

This middleware will return the following headers:

• X-RateLimit-Limit With the set request limit in RPM (taking in account if you specified a key and different quotas per key)
• Retry-After With the time in seconds the client should wait until he can issue another request. This is only sent if the limit has been reached