THIS IS A WORK IN PROGRESS

Ursa.

ursa is a Go package that provides a HTTP rate limiting proxy that can be used as a throttler in front of your server. Rate limiting is done based on configuration object provided. It supports rate limiting based on arbitrary header fields for arbitrary HTTP methods.

Installation

Install the package using go get

go get github.com/ursaserver/ursa/

Example

Create a simple rate limiter server. Note that this assumes you have a backend (that you want to setup a rate limiting for) running at port 8000 in your localhost. If you don't, you can test the code against python http.server by invoking python -m http.server 8000

Here's the code for your rate limiter. As you read the following code note that ursa allows you to:

1. Set up different rate limiting rules based on arbitrary header.
2. If you want to do rate limiting by IP, that's supported and setup for you.

package main

import (
	"net/http"
	"net/url"
	"regexp"

	"github.com/ursaserver/ursa"
)

func main() {
    // Create a ursa rate lmiter that is a proxy to your backend
    // Configuration is specified in a separate function for clarity
	ursaLimiter := ursa.New(conf())
	http.ListenAndServe(":3000", ursaLimiter)
}

func conf() ursa.Conf {
    // Define the kind of rates you'd like to use
	BaseRate := ursa.NewRate(5, ursa.Minute)
	UserRate := ursa.NewRate(60, ursa.Minute)

    // The IP address of your backend
	upstream, _ := url.Parse("http://localhost:8000")

    // Here, we are setting up a mechanism for by creating a
    // RateBy struct that lets us perform rate liming based on any 
    // header field (Authentication) in this case.
	RateByUser := ursa.NewRateBy(
		"Authentication", // Heder name
		// Update this function body to put in the logic for checking if the provided value is valid auth token
		// This function either has to go to database, or (better) if you're using JWT token you can just check if 
		// the signature is valid by running without doing anything that expensive
		func(s string) bool { return true },
		// Generate user id from the auth token. Otherwise users will keep generating new ID everytime current token expires.
		func(s string) string { return s },
		400,
		"Invalid authentication",
	)

	// Define the upstream server
	var conf ursa.Conf
	conf.Upstream = upstream

	conf.Routes = []ursa.Route{
		{
			Methods: []string{"GET"},
			Pattern: regexp.MustCompile(".*"),
			Rates: ursa.RouteRates{
				ursa.RateByIP:         BaseRate,
				RateByUser: UserRate,
			},
		},
	}
	return conf
}

Beware

1. Rate limiting by IP will deduct the tokens for users sharing the IP. This is a problem for organizational clients sitting under a common gateway. There's no workaround currently for public APIs. Use authenticated rate limting rules whenever possible (like RateByUser in the above example.)

TODOS

Benchmarking

Rate limiter binary

If you'd instead create a rate limiter without writing a server in go (although it's the recommended approach), checkout the ursaserver repo. It uses this ursa package under the hood but creates a rate limiter based on the JSON configuration provided.