notifier.rb

[Producer.new(pool, notifications_east, Notifier).thread,
 Producer.new(pool, notifications_west, Annotator).thread,
 Producer.new(pool, annotations_east, Annotator).thread,
 Producer.new(pool, annotations_west, Annotator).thread].each &:join

producer.rb

class Producer
  def initialize(pool, queue, work_class)
    @pool = pool
    @queue = queue
    @work_class = work_class
  end

  def post_work
    message = @queue.receive_message({attributes: [:all], wait_time_seconds: 15})
    @pool.post do
      begin
        @work_class.new(message).process_message
      rescue => e
        Rails.logger.warn "Exception while processing job: #{e}\n#{e.backtrace}"
      end
    end
  end

  def run
    loop { post_work }
  end

  def thread
    Thread.new { run }
  end
end