Ruby consumer for RabbitMQ queue with rate-limiting based on Redis

consumer.rb

#!/usr/bin/env ruby
# encoding utf-8

require 'bunny'
require 'logger'
require 'redis'

logger = Logger.new(STDOUT)
STDOUT.sync = true

conn = Bunny.new(host: 'rmq', user: 'guest', pass: 'guest')
conn.start

ch = conn.create_channel
q = ch.queue('work.queue', arguments: { :'x-dead-letter-exchange' => 'retry.exchange' })

Redis.current = Redis.new(host: 'redis')

# `block: true` is only for presentation purposes
# it blocks the main thread, do not use it in production
q.subscribe(manual_ack: true, block: true) do |delivery_info, properties, payload|
  logger.info "Message received with payload: #{payload}"
  key = "slot:#{Time.now.utc.sec}"
  slot = Redis.current.get(key)
  logger.info "Slot value: #{slot}"
  if !slot || slot.to_i < 1
    logger.info "Slot acquired, writing to Redis"
    result = Redis.current.multi do |multi|
      multi.set(key, 1)
      multi.expire(key, 1)
    end
    logger.info "Slot acquired, finished writing to Redis with result: #{result}"
    ch.ack(delivery_info.delivery_tag)
    logger.info "Message acked"
  else
    # reject without requeue
    ch.reject(delivery_info.delivery_tag)
    logger.info "Message rejected"
  end
end

conn.close