gistfile1.rb

# You could do it before, after save or in any place you want
before_save do   
  file = self.file #or group, or that ever your attribute is called
  
  # it is important to wrap it up in case remote call fails for any reason
  begin     
    response = file.copy true,  "#{target}"
    # {
    #   "url" : "http://..." 
    # }
    # do that you must. it is basicly JSON string.
  rescue
    # in case everything fails. 
    # it is not happens very ofter but your application can not depends on server status of any other server, right?
    # you may put it to query to call again in five minutes in separate process for example     
    logger.error "#{error text}"   
  end  
end