Chapters 4 & 5 of Packt’s Learning Ansible continue to build out strategies needed for enterprise class deployment and configuration management, for example error handling, rollback and reporting in chapter 4.  As chapter, the amount of new Ansible capabilities being introduced is not as substantive as prior chapters, and emphasis is more only what could be described as best practise. For example creating Playbooks that have the means to be invoked to re-establish a prior state if the the execution of the current playbook was to throw up an error.  The callback explanation does need a bit more understanding of how Python works as implementing a callback involves a little bit of Python coding, but the points into which you can hook actions is very rich.

From knowing how to trap callbacks it becomes possible to initiate notifications when events occur in playbooks which is where this chapter moves onto with monitoring and alerting. This really focuses on has my playbook executed as expected and reporting back through means such as email, nagios and graphite.  The examples with email and nagios miss a trick, although the text says you can incorporate output from tasks – it isn’t illustrated; yet if something falters you’d want to see the task output.

Chapter 5 goes into how you might write your own custom modules and test them. Ansible will support any language that is available in your target environment, although Python is the recommended language given its general availability and is the language used to write Ansible, and Ansible modules can be leveraged to shorten the effort in creating custom modules. The chapter then walks through examples using Python, Bash shell scripting and Ruby. A lot of the work appears to be centred on extracting the appropriate parameters to allow the module to run with. The final part of the chapter looks at testing with the Python Nose library.

Solid chapters, and perhaps a little shorter than the first few, but importantly continuing to be well written although perhaps a couple of small missed opportunities to be great chapters.

Prior chapter reviews:

• Learning Ansible Part 2
• Learning Ansible Part 1