MCollective is a powerful orchestration tool. Most of the work in MCollective is done by the middleware broker. Almost all of the problems with MCollective come down to broker communication. Always start by checking whether your nodes can connect to the broker and they have the correct user information to connect.
In the next chapter, we'll look at two Puppet components that use the Puppet Labs TrapperKeeper framework. We'll see how to debug issues with these two components.