Learning MCollective

Chapter 17. Creating a Client Application

We’ve done a bit of testing with the agent, doing direct RPCUtil queries against it. That’s a bit long of a command isn’t it? And look at all that messy RPCUtil output.

Why don’t we build a proper client plugin to interface with our new agent?

Baseline Client

Unfortunately, there’s no easy command to generate a template for us, so we’ll just have to do this ourselves. This application will be thanks/application/thanks.rb. Assuming you are still inside the thanks/agent/ directory from earlier:

$ mkdir ../application
$ cd ../application
$ $EDITOR thanks.rb

Now let’s populate the file like so (you can find this file in the source code supplied with the book):

class MCollective::Application::Thanks<MCollective::Application
  description "Sends a thanks message."
  usage "mco thanks [OPTIONS]"

  # This options parser updates the help page
  option :person,
         :description => "The person the dolphins say Goodbye to.",
         :arguments   => ["-p NAME", "--person NAME"],
         :type        => String,
         :require     => true

  # another hook where we could throw exceptions if the input isn't valid
  def validate_configuration(configuration)
    # this shouldn't happen since the option is mandatory above
    raise "Need to supply a person to get a reply." \
      unless configuration.include?(:person)
  end

  # Now we enter main processing
  def main
   client = rpcclient("thanks")
    printrpc client.say_goodbye(
      :person => configuration[:person],
      :options => options
    )

    # Exit using halt and it will pass on the ...