__redis_server_before.rb

require 'active_record'
require 'barrister'
require 'pry'
require 'redis'
require 'erb'

# App
require './models.rb'
require './service.rb'

# establish connection to main db
db_config = YAML.load(ERB.new(File.read('../../config/database.yml')).result)
RACK_ENV ||= ENV['RACK_ENV'] || 'development'
ActiveRecord::Base.establish_connection(db_config[RACK_ENV])

# establish connection to Redis
redis_config = YAML.load(ERB.new(File.read('../../config/redis.yml')).result)['user_service']
client = Redis.connect url: ENV['OPENREDIS_URL'] || redis_config['database_url']

# initialize service
contract = Barrister::contract_from_file('./user_service.json')
server   = Barrister::Server.new(contract)
server.add_handler('UserService', UserService.new)

while true
  # pop last element off our list in a blocking fashion
  channel, request = client.brpop(redis_config['list_name'])

  parsed = JSON.parse request

  # reverse the message we were sent
  response = {
    'message' => server.handle(parsed['message'])
  }

  # 'respond' by inserting our reply at the head of a 'reply'-list
  client.lpush(parsed['reply_to'], JSON.generate(response))
end

app.rb

require './service.rb'

container = Barrister::RedisContainer.new(ENV['REDIS_URL'], './user_service.json', UserService)
container.run

barrister_redis_container.rb

require 'barrister'
require 'redis'

module Barrister

  class RedisContainer
    
    def initialize(redis_url, json_path, service_klass, interface_name=nil)
      # establish connection to Redis
      @client    = Redis.connect url: ENV['OPENREDIS_URL']
      
      # communication channel for this container
      @list_name = service_klass.to_s

      # initialize service
      contract = Barrister::contract_from_file(json_path)
      @server  = Barrister::Server.new(contract)
      @server.add_handler(interface_name || service_klass.to_s, service_klass.new)
    end
    
    def run
      while true
        # pop last element off our list in a blocking fashion
        channel, request = client.brpop(@list_name)
      
        parsed = JSON.parse request
      
        # reverse the message we were sent
        response = {
          'message' => server.handle(parsed['message'])
        }
      
        # 'respond' by inserting our reply at the head of a 'reply'-list
        client.lpush(parsed['reply_to'], JSON.generate(response))
      end
    end
    
  end
  
end