Using multiple connections within a single model (method)

rails_multiple_connection

# Use pipe to transfer data between fork and parent process
reader, writer = IO.pipe

# Fork process to isolate the work with multiple database connections from application
pid = fork do
  reader.close()

  begin
    # if used Redis uncomment this line to reset connection
    # REDIS = Redis.new(:host => '', :port => '', :password => '')

    # In this point used application current database connections, :production
    # Fetch data from your_db database
    @model = YourModels.includes(:another_model).first

    # Switch database connection, in this point start using :production_fork connection
    ActiveRecord::Base.establish_connection :production_fork 
    @cloned_model = @model.dup

    # Model has been saved with :production_fork connection
    # Data has been saved in your_fork_db database
    @cloned_model.save

    writer.write(@cloned_model.id)
  rescue Exception => e
    print e.inspect
  ensure
    ActiveRecord::Base.remove_connection

    # If used Redis uncomment this line to disconnect
    # REDIS.client.disconnect if used

    Process.exit!
  end
end

Process.waitpid(pid, 0)

# In this point used again application current database connection, :production

writer.close()

# Print @cloned_model.id
print reader.read()