Rails:如何侦听/从服务或队列中提取消息? [英] Rails: How to listen to / pull from service or queue?

问题描述

大多数Rails应用程序的工作方式是等待客户端发出的请求，然后再发挥作用. 但是，如果我想将Rails应用程序用作微服务架构的一部分(例如)并进行一些异步通信(Serivce A将事件发送到Kafka或RabbitMQ队列中，而Service B-我的Rails应用程序-应该侦听此队列)，如何调整/启动Rails应用以立即侦听队列并从那里触发事件? (意味着初始触发不是来自客户端，而是来自应用程序本身.)

Most Rails applications work in a way that they are waiting for requests comming from a client and then do their magic. But if I want to use a Rails application as part of a microservice architecture (for example) with some asychonious communication (Serivce A sends an event into a Kafka or RabbitMQ queue and Service B - my Rails app - is supposed to listen to this queue), how can I tune/start the Rails app to immediately listen to a queue and being triggered by event from there? (Meaning the initial trigger is not comming from a client, but from the App itself.)

感谢您的建议！

推荐答案

我刚刚在应用程序中设置RabbitMQ消息传递，并将在第二天左右为分离的(多个分布式)应用程序实现.我发现这篇文章非常有帮助(而

I just set up RabbitMQ messaging within my application and will be implementing for decoupled (multiple, distributed) applications in the next day or so. I found this article very helpful (and the RabbitMQ tutorials, too). All the code below is for RabbitMQ and assumes you have a RabbitMQ server up and running on your local machine.

到目前为止，这是我的工作-对我有用:

Here's what I have so far - that's working for me:

  #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

我这样使用:

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

然后我有我的听众":

  # 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

侦听器"将消息发送到Messaging::EventsAgent.distribute，如下所示:

The 'listener' sends the message to Messaging::EventsAgent.distribute, which is like this:

  # 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上的说明进行操作，

Following the instructions on Codetunes, I have:

  # 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

并且:

  # 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.首先，我说(让我的监听器运行):

I open two console windows. In the first, I say (to get my listener running):

  $ 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

第二，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，在我的第一个窗口中，我看到:

Then, back in my first window, I see:

  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:

And in my RabbitMQ server, I see:

这是一个非常小的设置，我相信未来几天我会学到更多的东西.

It's a pretty minimal setup and I'm sure I'll be learning a lot more in coming days.

祝你好运！

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