Ratelimit: Slow your roll

Ratelimit provides a way to rate limit actions across multiple servers using Redis. This is a port of RateLimit.js found here and inspired by this post.

Add this line to your application's Gemfile:

gem 'ratelimit'

And then execute:

$ bundle

Or install it yourself as:

$ gem install ratelimit

My example use case is bulk processing data against an external API. This will allow you to limit multiple processes across multiple servers as long as they all use the same Redis database.

Add to the count for a given subject via add with a unique key. I've used the example of a phone number below but anything unique would work (URL, email address, etc.)

You can then fetch the number of executions for given interval in seconds via the count method.

ratelimit = Ratelimit.new("messages")
5.times do
  ratelimit.add(phone_number)
end
ratelimit.count(phone_number, 30)
# => 5

You can check if a given threshold has been exceeded or not. The following code checks if the currently rate is over 10 executions in the last 30 seconds or not.

ratelimit.exceeded?(phone_number, threshold: 10, interval: 30)
# => false
ratelimit.within_bounds?(phone_number, threshold: 10, interval: 30)
# => true

You can also pass a block that will only get executed if the given threshold is within bounds. Beware, this code blocks until the block can be run.

ratelimit.exec_within_threshold phone_number, threshold: 10, interval: 30 do
  some_rate_limited_code
  ratelimit.add(phone_number)
end

By default, Ratelimit will try to connect to a Redis server on 127.0.0.1:6379 and this works great when you have everything in one place. However, when you have a separate Redis server, you will need to make a few changes to specify its location.

To do so, instantiate a redis client pointing to the right server (if you don't have one instance already) and pass it in the constructor.

redis = Redis.new(host: "10.0.1.1", port: 6380, db: 15)
...
ratelimit = Ratelimit.new("messages", redis: redis)

Full documentation can be found here.

1. Fork it ( https://github.com/ejfinneran/ratelimit/fork )
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request