https://medium.com/@remie/using-dns-as-an-ansible-dynamic-inventory-e65a2ed6bc9

dynamic-inventory-for-ansible-with-dns

#!/usr/bin/env node

###########################################################################################
# Dynamic inventory for Ansible with DNS
# Author Remie Bolte (https://nl.linkedin.com/in/remiebolte)
#
# This NodeJS script generates a dynamic inventory based on DNS TXT records.
#
# If you use the “--inventory” switch when calling Ansible, you can provide the 
# path to a directory which includes inventory files. Ansible will automtically 
# run any executable script in that directory to see if provides the JSON output 
# describing a dynamic inventory.
#
# Using the following NodeJS script, you can read the information from your TXT 
# record and provide the JSON output that Ansible requires.
#
# This script will query the DNS server for the value of the TXT record associated 
# with “host._ansible.yourdomain.com”.
#
# It expects to retrieve a string-based value of:
# “hostname=web-host-01.yourdomain.com;sections=webserver,boston”
#
# The second TXT record might be:
# “hostname=db-host-01.yourdomain.com;sections=database,atlanta”
#
# The script will parse these TXT records and output the following JSON:
# { “webserver”: { “hosts”: [ “web-host-01.yourdomain.com” ] }, “boston”: { “hosts”: [ “web-host-01.yourdomain.com” ] }, “database”: { “hosts”: [ “db-host-01.yourdomain.com” ] }, “atlanta”: { “hosts”: [ “db-host-01.yourdomain.com” ] }
#
# Now you only need to create a script that updates your DNS when provisiong or 
# decommissioning a server, by either adding or removing the TXT record for that 
# specific host.
#
# TODO:
# - Add host variables
# - Add encryption/decription of TXT record metadata
#
# Copyright (c) 2016 Remie Bolte
# This snippet is license with the MIT open source license
# https://opensource.org/licenses/MIT
#
# Permission is hereby granted, free of charge, to any person obtaining a copy of 
# this software and associated documentation files (the "Software"), to deal in the 
# Software without restriction, including without limitation the rights to use, copy, 
# modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, 
# and to permit persons to whom the Software is furnished to do so, subject to the 
# following conditions:
#
# The above copyright notice and this permission notice shall be included in all copies 
# or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, 
# INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A 
# PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT 
# HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF 
# CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE 
# OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
#
###########################################################################################

// ------------------------------------------------------------------------------------------ Dependencies

var dns = require('dns');
var _ = require('lodash');
var program = require('commander');

// ------------------------------------------------------------------------------------------ Variables

// Replace 'yourdomain.com' in this variable with your DNS domain name
var domain = 'host._ansible.yourdomain.com';

// ------------------------------------------------------------------------------------------ Command-line parser

program
  .option('-l, --list', 'JSON list of sections/hosts')
  .option('-h, --host [hostname]', 'retrieve variables for specified host (not supported)')
  .parse(process.argv);

generateDynamicInventoryFromDNS(domain, function(inventory) {
	if(program.list) {
		// Return list of hosts
		return console.log(JSON.stringify(inventory));
	} else if (program.host) {
		// Host variables are currently not supported, returning empty object
		return console.log({});
	} else {
		// Wait... what?
		program.outputHelp();
	}
});

// ------------------------------------------------------------------------------------------ Private functions

function generateDynamicInventoryFromDNS(domain, callback) {
	// Retrieve TXT records from DNS
	dns.resolveTxt(domain, function(error, records) {

		// Variable that will contain the inventory
		var inventory = {};

		// Iterate over TXT records
		records.forEach(function(record) {

			// Find each key/value pair in TXT record
			var data = record[0].split(';');

			// temporary object to store key/value pairs
			var store = Array();

			_.each(data, function(items) {
				// Parse key/value pair and store them in temporary object
				var item = items.split("=");
				var key=item[0];
				var value=item[1];
				store[key] = value;
			});

			// Check if this host has sections or is ungrouped
			if(_.has(store, 'sections')) {

				// Iterate over the sections this host is assigned to
				_.each(store['sections'].split(','), function(section) {

					// Initialize section if it does not already exist
					if(!_.has(inventory, section)) {
						inventory[section] = {}
						inventory[section]['hosts'] = Array();
					};

					// Add host to inventory (unless it exists)
					if(!_.includes(inventory[section]['hosts'], store['hostname'])) {
						inventory[section]['hosts'].push(store['hostname']);
					}
				});
			} else {

				// Host is ungrouped
				// Initialize ungrouped section if it does not already exist
				if(!_.has(inventory, 'ungrouped')) {
					inventory['ungrouped'] = {};
					inventory['ungrouped']['hosts'] = Array();
				}

				// Add host to inventory (unless it exists)
				if(!_.includes(inventory['ungrouped']['hosts'], store['hostname'])) {
					inventory['ungrouped']['hosts'].push(store['hostname']);
				}
			};
		});

		callback(inventory);
	});
};