Rails:如何从服务或队列中侦听/拉取？

Question

大多数Rails应用程序的工作方式是它们等待来自客户端的请求然后发挥其魔力.但是,如果我想使用Rails应用程序作为微服务架构的一部分(例如)与一些非常好的通信(Serivce A将事件发送到Kafka或RabbitMQ队列和服务B - 我的Rails应用程序 - 应该监听此队列),如何调整/启动Rails应用程序以立即收听队列并由来自那里的事件触发？(这意味着初始触发器不是来自客户端,而是来自应用程序本身.)

谢谢你的建议!

Answer 1

我只是在我的应用程序中设置RabbitMQ消息传递,并将在第二天左右实现解耦(多个,分布式)应用程序.我发现这篇文章非常有用(以及RabbitMQ教程).以下所有代码均适用于RabbitMQ,并假设您已在本地计算机上启动并运行RabbitMQ服务器.

这是我到目前为止所做的 - 这对我有用:

  #Gemfile
  gem 'bunny'
  gem 'sneakers'

我有一个Publisher发送到队列:

  # app/agents/messaging/publisher.rb
  module Messaging
    class Publisher
      class << self

        def publish(args)
          connection = Bunny.new
          connection.start
          channel = connection.create_channel
          queue_name = "#{args.keys.first.to_s.pluralize}_queue"
          queue = channel.queue(queue_name, durable: true)
          channel.default_exchange.publish(args[args.keys.first].to_json, :routing_key => queue.name)
          puts "in #{self}.#{__method__}, [x] Sent #{args}!"
          connection.close
        end

      end
    end
  end

我用的是这样的:

  Messaging::Publisher.publish(event: {... event details...})

然后我有了'倾听者':

  # app/agents/messaging/events_queue_receiver.rb
  require_dependency "#{Rails.root.join('app','agents','messaging','events_agent')}"

  module Messaging
    class EventsQueueReceiver
      include Sneakers::Worker
      from_queue :events_queue, env: nil

      def work(msg)
        logger.info msg
        response = Messaging::EventsAgent.distribute(JSON.parse(msg).with_indifferent_access)
        ack! if response[:success]
      end

    end
  end

'listener'将消息发送给Messaging::EventsAgent.distribute,如下所示:

  # app/agents/messaging/events_agent.rb
 require_dependency  #{Rails.root.join('app','agents','fsm','state_assignment_agent')}"

  module Messaging
    class EventsAgent
      EVENT_HANDLERS = {
        enroll_in_program: ["FSM::StateAssignmentAgent"]
      }
      class << self

        def publish(event)
          Messaging::Publisher.publish(event: event)
        end

        def distribute(event)
          puts "in #{self}.#{__method__}, message"
          if event[:handler]
            puts "in #{self}.#{__method__}, event[:handler: #{event[:handler}"
            event[:handler].constantize.handle_event(event)
          else
            event_name = event[:event_name].to_sym
            EVENT_HANDLERS[event_name].each do |handler|
              event[:handler] = handler
              publish(event)
            end
          end
          return {success: true}
        end

      end
    end
  end

按照Codetunes的说明,我有:

  # Rakefile
  # Add your own tasks in files placed in lib/tasks ending in .rake,
  # for example lib/tasks/capistrano.rake, and they will automatically be available to Rake.

  require File.expand_path('../config/application', __FILE__)

  require 'sneakers/tasks'
  Rails.application.load_tasks

和:

  # app/config/sneakers.rb
  Sneakers.configure({})
  Sneakers.logger.level = Logger::INFO # the default DEBUG is too noisy

我打开两个控制台窗口.在第一个,我说(让我的听众运行):

  $ WORKERS=Messaging::EventsQueueReceiver rake sneakers:run
  ... a bunch of start up info
  2016-03-18T14:16:42Z p-5877 t-14d03e INFO: Heartbeat interval used (in seconds): 2
  2016-03-18T14:16:42Z p-5899 t-14d03e INFO: Heartbeat interval used (in seconds): 2
  2016-03-18T14:16:42Z p-5922 t-14d03e INFO: Heartbeat interval used (in seconds): 2
  2016-03-18T14:16:42Z p-5944 t-14d03e INFO: Heartbeat interval used (in seconds): 2

在第二个,我说:

  $ rails s --sandbox
  2.1.2 :001 > Messaging::Publisher.publish({:event=>{:event_name=>"enroll_in_program", :program_system_name=>"aha_chh", :person_id=>1}})
  in Messaging::Publisher.publish, [x] Sent {:event=>{:event_name=>"enroll_in_program", :program_system_name=>"aha_chh", :person_id=>1}}!
  => :closed 

然后,回到我的第一个窗口,我看到:

  2016-03-18T14:17:44Z p-5877 t-19nfxy INFO: {"event_name":"enroll_in_program","program_system_name":"aha_chh","person_id":1}
  in Messaging::EventsAgent.distribute, message
  in Messaging::EventsAgent.distribute, event[:handler]: FSM::StateAssignmentAgent

在我的RabbitMQ服务器中,我看到:

这是一个非常小的设置,我相信在接下来的几天里我会学到很多东西.

祝好运!