Rapidity

Simple but fast Redis-backed distributed rate limiter. Allows you to specify time interval and count within to limit distributed operations.

Features:

• extremly simple
• free from race condition through LUA scripting
• fast

Article(russian) about gem.

Usage

Rapidity has two variants:

• simple Rapidity::Limiter to handle single distibuted counter
• complex Rapidity::Composer to handle multiple counters at once

Single conter with concurrent access

pool = ConnectionPool.new(size: 10) do
  Redis.new(url: ENV.fetch('REDIS_URL', 'redis://127.0.0.1:6379'))
end

# allow no more 10 requests within 5 seconds
limiter = Rapidity::Limiter.new(pool, name: 'requests', threshold: 10, interval: 5)

loop do
  # try to obtain 3 requests at once
  quota = limiter.obtain(3).times do
    make_request
  end

  if quota == 0
    # no more requests allowed within interval
    sleep 1
  end
end

Multiple counters

pool = ConnectionPool.new(size: 10) do
  Redis.new(url: ENV.fetch('REDIS_URL', 'redis://127.0.0.1:6379'))
end

LIMITS = [
  { interval: 1, threshold: 2 },        # no more 2 requests per second
  { interval: 60, threshold: 200 },     # no more 200 requests per minute
  { interval: 86400, threshold: 10000 } # no more 10k requests per day
]

limiter = Rapidity::Composer.new(pool, name: 'requests', limits: LIMITS)

loop do
  # try to obtain 3 requests at once
  quota = limiter.obtain(3).times do
    make_request
  end

  if quota == 0
    # no more requests allowed within interval
    puts limiter.remains # inspect current limits
    sleep 1
  end
end

Installation

It’s a gem:

  gem install rapidity

There’s also the wonders of the Gemfile:

  gem 'rapidity'

Special Thanks

• WeTransfer/prorate for LUA-examples