Ansible Dict and Tags - ansible

Question

I have a playbook creating EC2 by using a dictionary declared in vars: then registering the IPs into a group to be used later on.
The dict looks like this:
servers:
serv1:
name: tag1
type: t2.small
region: us-west-1
image: ami-****
serv2:
name: tag2
type: t2.medium
region: us-east-1
image: ami-****
serv3:
[...]
I would like to apply tags to this playbook in the simplest way so I can create just some of them using tags. For example, running the playbook with --tags tag1,tag3 would only start EC2 matching serv1 and serv3.
Applying tags on the dictionary doesn't seem possible and I would like to avoid doing multiplying tasks like:
Creatinge EC2
Register infos
Getting private IP from previously registered infos
adding host to group
While I already have a working loop for the case I want to create all EC2 at once, is there any way to achieve that (without relying on --extra-vars, which would need key=value) ? For example, filtering out the dictionary by keeping only what is tagged before running the EC2 loop ?

Answer 1

I doubt you can do this out of the box. And not sure this is good idea at all.
Because tags are used to filter tasks in Ansible, so you will have to mark all tasks with tags: always.
You can accomplish this with custom filter plugin, for example (./filter_plugins/apply_tags.py):
try:
from __main__ import cli
except ImportError:
cli = False
def apply_tags(src):
if cli:
tags = cli.options.tags.split(',')
res = {}
for k,v in src.iteritems():
keep = True
if 'name' in v:
if v['name'] not in tags:
keep = False
if keep:
res[k] = v
return res
else:
return src
class FilterModule(object):
def filters(self):
return {
'apply_tags': apply_tags
}
And in your playbook:
- debug: msg="{{ servers | apply_tags }}"
tags: always

Answer 2

I found a way to match my needs without touching to the rest so I'm sharing it in case other might have a similar need.
I needed to combine dictionaries depending on tags, so my "main" dictionary wouldn't be static.
Variables became :
- serv1:
- name: tag1
type: t2.small
region: us-west-1
image: ami-****
- serv2:
- name: tag2
type: t2.medium
region: us-east-1
image: ami-****
- serv3:
[...]
So instead of duplicating my tasks, I used set_fact with tags like this:
- name: Combined dict
# Declaring empty dict
set_fact:
servers: []
tags: ['always']
- name: Add Server 1
set_fact:
servers: "{{ servers + serv1 }}"
tags: ['tag1']
- name: Add Server 2
set_fact:
servers: "{{ servers + serv2 }}"
tags: ['tag2']
[..]
20 lines instead of multiply tasks for each server, change vars from dictionary to lists, a few tags and all good :) Now if I add a new server it will only take a few lines.