Ansible and reloading AWS dynamic inventory

amazon-web-servicesansible

See also: https://stackoverflow.com/questions/29003420/reload-ansibles-dynamic-inventory.

My question: is there a better way of doing what's below?

I have an ansible role that provisions AWS machines, and runs correctly (notice the provision tag):

- name: AWS provision
  hosts: localhost
  gather_facts: no
  vars_files:
    - vars/dev.yml
  user: ec2-user
  roles:
    - provision
  tags:
    - provision

I then have a base role, that I want to be able to run independently (for example during development, so I don't have to wait for re-provisioning (notice the base tag). I run a play find running instances that filters and stores the hosts in the group started:

- name: find running instances
  hosts: localhost
  vars_files:
    - vars/dev.yml
  gather_facts: no
  tags:
    - base
  tasks:
    - name: gather remote facts
      ec2_remote_facts:
        region: "{{ target_aws_region }}"
        filters:
          instance-state-name: running
          "tag:Name": "{{ instance_name }}"
      register: ec2_facts

    - debug: var=ec2_facts

    - name: add hosts to groups
      add_host:
        name: "{{ item.id }}"
        ansible_ssh_host: "{{ item.public_dns_name }}"
        groups: started
      changed_when: false
      with_items: ec2_facts.instances

- name: base setup
  hosts: started
  gather_facts: no
  vars_files:
    - vars/dev.yml
  user: ec2-user
  roles:
    - base
  tags:
    - base

My question: the plays are working, but is there a better way of doing this? For example I'm got gather_facts: no followed by ec2_remote_facts and the filters – it all seems rather convoluted.

A clarification: thanks for the comment about ec2.py — I'm already using it in my first play (when I call the provision role).

But for testing purposes I want to jump into subsequent plays without re-doing the (slow) provisioning. So how do I re-populate my hosts data? Is ec2_remote_facts followed by add_host the right way? Or can I somehow use gather_facts: yes?

Best Answer

I'd probably use the EC2 dynamic inventory script instead, which you can employ by configuring ec2.ini and passing -i ec2.py to ansible-playbook.

See http://docs.ansible.com/ansible/intro_dynamic_inventory.html#example-aws-ec2-external-inventory-script for more info.

Note that there are plenty of options in ec2.ini. Be sure to have a look at those, e.g. cache_max_age. You can also make the inventory generation faster by filtering unnecessary resources (e.g. set rds = False if you are only interested in EC2 instances).

UPDATE: With Ansible 2.x+ you can also use - meta: refresh_inventory mid-play.

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