Building Ansible Modules with Perl and Mojolicious

2014-10-05 − 🏷 perl 🏷 ansible

While setting up Output, we decided to automate all our infrastructure using Ansible. This lets us easily do zero downtime releases and create new workers as needed to scale. We’ve got roles for haproxy, postgresql, nginx, our app servers and a lot more. One thing we’ve been handling manually so far is DNS. We’re happy Cloudflare users, and they have one of the best DNS admin tools I’ve used, but still I felt like we could do better.

My friend Jan Henning also felt this way, and had already written Mojo::Cloudflare, a simple API client for Cloudflare. Even tho Ansible is Python-based, you can write your plugins in whatever language you like, so I decided to glue the two together. This turned out to be quite easy. First you need to tell ansible you can handle json:

#!/usr/bin/env perl

Then we get the module argument file from the args, and parse the JSON:

use Mojo::JSON;
use Mojo::Util qw/slurp/;

my $json = Mojo::JSON->new;
my $args = $json->decode(slurp($ARGV[0]));

And then you just process those arguments and do your thing. Lets say you want to check for required arguments:

for (qw/email api_key zone name/) {
  fail("$_ is a required argument") unless exists $args->{$_};

My fail method looks like this:

sub fail {
  my $msg = shift;
  print $json->encode({failed => 1, message => $msg});
  exit 1;

The important thing here is to exit 1, the json response is icing on the cake. For success you could could do something like this:

print $json->encode({changed => \$changed, record => $current->id});

Note the bool reference to make Mojo::JSON return true/false. $changed will make the difference between OK and CHANGED output in your ansible run.

Put your module in a library/ sub directory of your playbook folder, and you can just use it in your playbook like this:

local_action: cloudflare name=sentry type=CNAME service_mode=1 email={{cloudflare_user}}

I store my Cloudflare credentials in an ansible-vault and just include that in my playbook. Note that using this module will require having the latest version of Mojo::Cloudflare installed. If you want to run it on the remote server rather than as a local_action, that server must also have the module.

Anyways, if you want to try it yourself, you can find the latest version of my cloudflare ansible module here.