MCollective Release 0.4.x

A few days ago I released Marionette Collective version 0.4.0 and today I released 0.4.1. This release branch introduce a major new feature called Simple RPC.

In prior releases it took quite a bit of ruby knowledge to write a agent and client. In addition clients all ended up implementing their own little protocols for data exchange. We’ve simplified agents and clients and we’ve created a standard protocol between clients and agents.

Standard protocols between clients and agents means we have a standard one-size-fits-all client program called mc-rpc and it opens the door to writing simple web interfaces that can talk to all compliant agents. We’ve made a test REST Simple RPC bridge as an example.

Writing a client can now be done without all the earlier setup, command line parsing and so forth, it can now be as simple as:

require 'mcollective'
 
include MCollective::RPC
 
mc = rpcclient("rpctest")
 
printrpc mc.echo(:msg => "Welcome to MCollective Simple RPC")
 
printrpcstats

This simple client has full discovery, full –help output, and takes care of printing results and stats in a uniform way.

This should make it much easier to write more complex agents, like deployers that interact with packages, firewalls and services all in a single simple script.

We’ve taken a better approach in presenting the output from clients now, instead of listing 1000 OKs on success it will now only print whats failing.

Output from above client would look something along these lines:

$ hello.rb
 
 * [ ============================================================> ] 43 / 43
 
Finished processing 43 / 43 hosts in 392.60 ms

As you can see we have a nice progress indicator that will work for 1 or 1000 nodes, you can still see status of every reply by just running the client in verbose – which will also add more detailed stats at the end.

Agents are also much easier, here’s a echo agent:

class Rpctest<RPC::Agent
    def echo_action
         validate :msg, :shellsafe
 
         reply.data = request[:msg]
    end
end

You can get full information on this new feature here. We’ve also created a lot of new wiki docs about ActiveMQ setup for use with MCollective and we’ve recorded a new introduction video here.