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# services/mail_service/implementation.rb

class MailService

  def send_email(from, to, subject, body)
    opts = { from: from, to: to, subject: subject, body: body }
    mail = ActionMailer::Base.mail opts
    !!mail.deliver # return true if we're g2g
  end

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# services/user_service/implementation.rb

class UserService

  USER_ATTRIBUTES = %w(id full_name email phone_number)
  
  def initialize(mail_service)
    @mail_service = mail_service
  end
  

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# services/user_service/models/user.rb

class UserService

  class User < ActiveRecord::Base
    validates :email, uniqueness: true
  end

end

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# config/initializers/services.rb

require 'barrister-rails'

class Services

  def self.user_service
    @@services ||= proxy_services
    @@services[:user_service]
  end

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class UsersController < ApplicationController

  # ...

  def create
    Services.user_service.create_user user_params    
    redirect_to action: 'index'
  end

  # ...

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# services/mail_service/main.rb

require 'barrister-redis'

opts = { 
  database_url: ENV['OPENREDIS_URL'],
  list_name: 'mail_service'
}

Barrister::RedisContainer.new('./interface.json',  MailService.new, opts).start

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# services/user_service/main.rb

require 'activerecord'
require 'barrister-redis'

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

# create our MailService proxy

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# config/initializers/services.rb

require 'barrister-rails'
require 'barrister-redis'

class Services

  # ...
  
  def self.proxy_services

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# Procfile

web: bundle exec rails s -p $PORT

mail_service: sh -c 'cd services/mail_service; ./main.rb'

user_service: sh -c 'cd services/user_service; ./main.rb'

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# services/mail_service/main.rb

require 'barrister-sinatra'

opts = { 
  mount_path: '/api',
  port: ENV['PORT']
}

Barrister::SinatraContainer.new('./interface.json',  MailService.new, opts).start