Ansible handlers by default are run at the end of the actual execution of a playbook. They are different from registers in that they provide us with a way of creating a set of automation that can be executed once (and only once) at the end of a playbook based on a set of conditions provided during the execution. Logically, this could look something like the following:
- Run role
foo - Run role
bar:- If role
bar's service start failed, trigger a flag
- If role
- Execute handlers:
- If a trigger was flagged, do something
While this example may seem similar in some ways to conditionals, it is in many ways very different. That is to say, the handler would only get executed the one time regardless of how many times the flag was tripped. In addition, the other variance would be that a handler is more global in nature. That is to say, regardless of which role tripped the flag of the handler, it would still get executed, thus making the solution non-modular. Confused? Let's take a look at an example of...