Я хочу писать хороший код! – Виды запашка (Code Smells) – kind_of? instance_of? is_a?

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Я хочу писать хороший код! – Виды запашка (Code Smells) – kind_of? instance_of? is_a?

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RabbitMQ and Rails

Messaging for Rails application with microservice architecture

Created by Evgeniy Burdaev

Что такое RabbitMQ?

RabbitMQ - это брокер сообщений, используя который сервисы принимают и отдают сообщения.

Простейший пример "Producer"-a, очереди и "Consumer"-a

Элементы

Producer

Exchange

Queue

Consumer

Веер

Прямой

Пример архитектуры приложения

Producer (Blog)

class Publisher
  def self.publish(exchange, message = {})
    x = channel.fanout("blog.#{exchange}")
    x.publish(message.to_json)
  end

  def self.channel
    @channel ||= connection.create_channel
  end

  def self.connection
    @connection ||= Bunny.new.tap do |c|
      c.start
    end
  end

  #ALTERNATE SYNTAX

  # def self.client
  #   @client ||= Bunny.new
  # end

  # def self.connection
  #   @connection || = client.start
  # end
end

Публикация события

<BLOG>
        # blog/app/controllers/posts_controller.rb
        class PostsController < ApplicationController
          # ...

          def create
            @post = Post.new(post_params)

            if @post.save
              # Publish post data
              Publisher.publish("posts", @post.attributes)

              redirect_to @post, notice: 'Post was successfully created.'
            else
              render :new
            end
          end

          # ...
        end
</>

Consumer (dashboard)

class RecentPosts
  KEY = "recent_posts" # redis key
  STORE_LIMIT = 5      # how many posts should be kept

  # Get list of recent posts from redis
  # Since redis stores data in binary text format
  # we need to parse each list item as JSON
  def self.list(limit = STORE_LIMIT)
    $redis.lrange(KEY, 0, limit-1).map do |raw_post|
      JSON.parse(raw_post).with_indifferent_access
    end
  end

  # Push new post to list and trim it's size
  # to limit required storage space
  # `raw_post` is already a JSON string
  # so there is no need to encode it as JSON
  def self.push(raw_post)
    $redis.lpush(KEY, raw_post)
    $redis.ltrim(KEY, 0, STORE_LIMIT-1)
  end
end

Достаем из редиса

# dashboard/app/controllers/home_controller.rb
class HomeController < ApplicationController
  def index
    @posts = RecentPosts.list
  end
end

Зависимости

# dashboard/Gemfile
gem 'redis-rails'
gem 'redis-namespace'
gem 'sneakers'

Snearkers (Worker) 

class PostsWorker
  include Sneakers::Worker
  # This worker will connect to "dashboard.posts" queue
  # env is set to nil since by default the actuall queue name would be
  # "dashboard.posts_development"
  from_queue "dashboard.posts", env: nil

  # work method receives message payload in raw format
  # in our case it is JSON encoded string
  # which we can pass to RecentPosts service without
  # changes
  def work(raw_post)
    RecentPosts.push(raw_post)
    ack! # we need to let queue know that message was received
  end
end
Запуск воркеров 
WORKERS=PostsWorker rake sneakers:run
\>

Осталось только все соединить

#rake task
namespace :rabbitmq do
  desc "Setup routing"

  task :setup do
    require "bunny"

    puts 'rabbit mq subscription'

    conn = Bunny.new
    conn.start

    ch = conn.create_channel

    # get or create exchange
    x = ch.fanout("blog.posts")

    # get or create queue (note the durable setting)
    queue = ch.queue("dashboard.posts", durable: true)

    # bind queue to exchange
    queue.bind("blog.posts")

    conn.close
  end
end

Вопросы предложения пожелания

- Основная статья с блога CODETUNES - Документация к гему bunny, а также гайды

RabbitMQ and Rails Messaging for Rails application with microservice architecture Created by Evgeniy Burdaev