rate limit

application_controller.rb

  rescue_from RateLimit::ExceededError do |e|
    render(json: errors_json(e.message), status: 429)
  end

Gemfile

# ...

gem 'redis'

rate_limit.rb

require 'redis'

module RateLimit
  class ExceededError < StandardError
    def initialize(wait_time)
      @wait_time = wait_time
    end

    def message
      "Please wait for #{@wait_time} seconds before repeating the request"
    end
  end

  def self.shape!(action:, limit:, interval: 3600)
    raise ArgumentError.new('action cannot be blank') if action.blank?
    raise ArgumentError.new('limit must be greater than 0') if limit <= 0

    keys = Redis.current.keys("rate_limit:#{action}:*")
    time_sec = Time.zone.now.to_i
    if keys.size >= limit
      wait = interval - (time_sec - Redis.current.get(keys.last).to_i).abs
      raise RateLimit::ExceededError.new(wait.to_s)
    else
      key = "rate_limit:#{action}:#{time_sec}.#{Time.zone.now.usec}"
      Redis.current.set(key, time_sec, ex: interval)
    end
  end

  def self.cleanup(action)
    raise ArgumentError.new('action cannot be blank') if action.blank?

    keys = Redis.current.keys("rate_limit:#{action}:*")
    Redis.current.del(keys) unless keys.empty?
  end
end

rate_limit_spec.rb

describe RateLimit do
  describe 'public methods' do
    before { Redis.current.flushall }

    describe 'shape!' do
      context 'validates params' do
        describe 'action' do
          it 'valid when action present' do
            expect { RateLimit.shape!(action: 'verb', limit: 1) }.not_to raise_error
          end

          it 'invalid when action blank' do
            expect { RateLimit.shape!(action: '', limit: 1) }.to raise_error(ArgumentError, 'action cannot be blank')
          end
        end

        describe 'limit' do
          it 'valid when limit present' do
            expect { RateLimit.shape!(action: 'verb', limit: 1) }.not_to raise_error
          end

          it 'invalid when limit not greater than 0' do
            expect { RateLimit.shape!(action: 'verb', limit: 0) }
              .to raise_error(ArgumentError, 'limit must be greater than 0')
          end
        end
      end

      context 'when rate not exceeded' do
        before { Timecop.freeze('2012-11-22T08:00:00-0500') }

        it 'saves action to log' do
          expect(Redis.current.keys('rate_limit:*').size).to eq 0
          expect { RateLimit.shape!(action: 'make_pies', limit: 5) }.not_to raise_error
          expect(Redis.current.keys('*')).to eq ['rate_limit:make_pies:1353589200.0']
        end
      end

      context 'when rate exceeded' do
        before { Timecop.freeze('2012-11-22T08:00:00-0500') }

        it 'raises exception' do
          RateLimit.shape!(action: 'make_pies', limit: 1)
          Timecop.freeze('2012-11-22T08:10:00-0500')
          expect { RateLimit.shape!(action: 'make_pies', limit: 1) }
            .to raise_error(RateLimit::ExceededError) do |e|
              expect(e.message).to eq 'Please wait for 3000 seconds before repeating the request'
            end
        end
      end
    end

    describe 'cleanup' do
      before do
        3.times { RateLimit.shape!(action: 'make_pies', limit: 10) }
        2.times { RateLimit.shape!(action: 'make_cookies', limit: 10) }
      end

      it 'removes previous records' do
        expect(Redis.current.keys.size).to eq 5
        expect(Redis.current.keys('rate_limit:make_pies:*').size).to eq 3
        expect(Redis.current.keys('rate_limit:make_cookies:*').size).to eq 2

        RateLimit.cleanup('make_pies')

        expect(Redis.current.keys.size).to eq 2
        expect(Redis.current.keys('rate_limit:make_pies:*').size).to eq 0
        expect(Redis.current.keys('rate_limit:make_cookies:*').size).to eq 2
      end
    end
  end
end

usage.rb

# in some controller action
def some_action
  # allow few invalid passwords to be entered, until doorkeeper rescue will be solved
  RateLimit.shape!(action: "3rdparty:buzzsumo", limit: ENV['BUZZSUMO_REQUESTS_PER_SECOND'].to_i)
  
  # ...
  
  if success?
    RateLimit.cleanup("3rdparty:buzzsumo")
  end
end