Update 2022-10-17: This is a copy of the review of a book that was kindly made available by UKUUG.

Learning MCollective
Jo Rhett
O'Reilly Media
ISBN: 978-1-491-94567-4
Published: August 2014

MCollective (M for Marionette, as in puppet!) is a Ruby based software framework from Puppet Labs for orchestrating configuration changes across Puppet or Chef based groups of servers.

MCollective communicates with the servers under its control through a message broker, currently only ActiveMQ and RabbitMQ are supported. The main text along with the examples only covers ActiveMQ, however, those who prefer RabbitMQ are provided with guidance in the appendix.

The book is divided into four parts that take the reader from initial installation of the base software to writing custom plugins.

Part I, Getting Started, takes the reader through the basic installation and configuration of the software, MCollective and ActiveMQ. It then proceeds to introduce, with examples, the main command line interface, mco. Although, there are web clients for the software, we are urged to stay with the command line.

Moving along, we are introduced to the basic workings of MCollective plugins and agents, as well as brief tips on system level maintenance, such as time sync, log files, monitoring etc. We are then shown how to configure MCollective with puppet and chef, yes it does sound like a chicken and egg situation, but the modules are there for us to use.

Those with a large enterprise installation are catered for in part II, Complex Installations. The message broker plays a very critical role in an MCollective based environment. In the next five chapters the reader is given guidance on how to create broker networks to aid scalability and resilience, as well as using certificates to make the message broker(s) more secure. Admittedly, I only skimmed over this part, but I am planning on a more through read at a later date.

As one can expect with any framework these days, MCollective comes equipped with the ability to create and use plugins. Part III, Custom Plugins, provides various examples of plugins and walks the reader through creating and deploying them.

Finally part IV, Putting It All Together, sums up the preceding chapters, provides a set of best practices and gives guidance on expanding the MCollective deployment.

I had a play with the command line examples on a Vagrant/VirtualBox based demo environment that is provided by Puppet Labs, all good fun, and no surprises there. The example codes and related data files used in the book have been made available on Rhett’s github repository.

Throughout the book, there are numerous hyperlinks for additional material, however, they are all Bit.ly shortcuts, which means the reader of the paper copy of the book will need to type in the links manually. It would be nice if the author could include these on a web page, or somewhere on the book’s github repository.

Overall, this book covers a lot of ground, going beyond a mere introduction to the basics of the framework. Although, its main focus is on Puppet and ActiveMQ, those who prefer Chef and/or RabbitMQ can still benefit from the text.