Changing a deeply-nested dict variable in an Ansible playbook

I recently had to build an Ansible playbook that takes in a massive inventory structure (read from a YAML file), modifies a specific key in that file, then dumps the file back to disk. There are some other ways that may be more efficient standalone (e.g. using a separate Python/PHP/Ruby/etc. script and a good YAML library), but since I had to do a number of other things in this Ansible playbook, I thought it would keep it simple if I could also modify the key inside the playbook.

I was scratching my head for a while, because while I knew that I could use the dict | combine() filter to merge two dicts together (this is a feature that was introduced in Ansible 2.0), I hadn't done so for a deeply-nested dict.

Easily manage Apache VirtualHosts with Ansible and Jinja2

Server Check.in's entire infrastructure is managed via Ansible, which has helped tremendously as the service has grown from one to many servers.

Ansible Borg Cow
cowsay and Ansible were made for each other.

One pain point with running Apache servers that host more than one website (using name-based virtual hosts) is that the virtual host configuration files quickly get unwieldy, as you have to define the entire <virtualhost></virtualhost> for every domain you have on the server, and besides Apache's mod_macro, there's no easy way to define a simple structured array of information and have the vhost definitions built from that.