Congestion

A Redis rate limiter that provides both time-based limits and quantity-based limits based on classdojo/rolling-rate-limiter.

Middleware

• Sidekiq-Congestion
• Rack-Congestion

Installation

Add this line to your application's Gemfile:

gem 'congestion'

And then execute:

$ bundle

Or install it yourself as:

$ gem install congestion

Usage

Making requests

limiter = Congestion.request 'some_key'

Where 'some_key' is an identifier for this request.

A common use case might be to set rate limits per user with something like "#{ user.id }_some_key".

Congestion.request returns an an instance that provides information about the request:

limiter.allowed?      # => true if the request is permitted
limiter.rejected?     # => true if the request is not permitted
limiter.too_many?     # => true if there are too many requests in the interval
limiter.too_frequent? # => true if the requests are arriving too quickly
limiter.backoff       # => the number of seconds before a request will be permitted

Configuration

A proc provides a Redis connection:

Congestion.redis = ->{
  Redis.new url: 'redis://:password@host:port/db'
}

To pool, your Redis connections:

require 'congestion/redis_pool'

Congestion::RedisPool.redis_config = {
  url: 'redis://:password@host:port/db'
}

Congestion::RedisPool.pool_size = 10  # number of connections to use
Congestion::RedisPool.timeout = 10    # seconds before timing out an operation

Congestion.redis = Congestion::RedisPool.instance

Global options can be set with:

Congestion.default_options = {
  namespace: 'congestion' # The Redis key prefix (e.g. 'congestion:some_key')
  interval: 1,            # The timeframe to limit within in seconds
  max_in_interval: 1,     # The number of allowed requests within the interval
  min_delay: 0.0,         # The minimum amount of time in seconds between requests
  track_rejected: true    # True if rejected request count towards the limit
}

Per-request options can be set as well:

Congestion.request 'some_key', interval: 60, min_delay: 1

Development

After checking out the repo, run bin/setup to install dependencies. Then, run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To run the specs, run bundle exec rake.

Contributing

1. Fork it ( https://github.com/parrish/congestion/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