Dynamic Inventory with Ansible

How to setup dynamic inventory with Ansible

Using dynamic inventory for Ansible

Video Tutorial

Initial Setup

Prerequisites:

• Install and setup Ansible
• Install boto (version>=2.24.0)

Get the ec2.ini and ec2.py file.

Make sure the ec2.py you are using should have --profile option . Use the latest ec2.py and boto with version>=2.24.0

Make the script executable by command chmod +x ec2.py

Configure the file ec2.ini file to work for particular region as shown below. this would decrease the execution time as the search for the resource would get limited to a particular region.

regions = us-east-1

Change ansible configuration file, ansible.cfg, to point to ec2.py as a host file

[defaults]
remote_user = root
host_key_checking = False
inventory = ./inventory/ec2.py

Now test the setup by running ./ec2.py --list. This should give the list of resources in the region we have se specified. If you get an error like below

region name: ap-south-1 likely not supported, or AWS is down.

Add the ap-south-1 region in the regions_exclude in ec2.ini file.

regions_exclude = us-gov-west-1,cn-north-1,ap-south-1

This will  remove the error and will list the resources as expected.

Writing  Playbook

First, define some default variable in a file all.yml in group_vars directory

mkdir group_vars
vi group_vars.all.yml

Add the following variables

---
# group_vars/all.yml
 
image: ami-7243e611
subnet: subnet-417fff25
region: ap-southeast-1
zone: ap-southeast-1a # zone that the master AMI will be configured in
keypair: mykey
security_groups: sample_subnet
instance_type: t2.micro

volumes:
  - device_name: /dev/xvda
    device_type: gp2
    volume_size: 8 # size of the root disk
    delete_on_termination: true

Let's create a role to launch an ec2 instance

mkdir -p roles/launch/tasks
vi roles/launch/tasks/main.yml

# roles/launch/tasks/main.yml

- name: Launch new instance
  ec2:
    region: "{{ region }}"
    vpc_subnet_id: "{{ subnet }}"
    keypair: "{{ keypair }}"
    zone: "{{ zone }}"
    group: "{{ security_groups }}"
    image: "{{ image }}"
    instance_type: "{{ instance_type }}"
    instance_tags:
      Name: "{{ name }}"
    volumes: "{{ volumes }}"
    wait: yes
    assign_public_ip: yes
  register: ec2
 
- name: Add new instances to host group
  add_host:
    name: "{{ item.public_dns_name }}"
    groups: "{{ name }}"
    ec2_id: "{{ item.id }}"
  with_items: "{{ ec2.instances }}"

- name: Wait for instance to boot
  wait_for:
    host: "{{ item.public_dns_name }}"
    port: 22
    delay: 30
    timeout: 300
    state: started
  with_items: "{{ ec2.instances }}"

vi launch_instance.yml

---
# launch_instance.yml
  - hosts: localhost
    connection: local
    gather_facts: no
    roles:
      - role: launch
        name: "{{ group_name }}-role-name"

Now simply run the playbook launch_instance.yml with the following command.

AWS_PROFILE=personal ansible-playbook -i hosts -e group_name=example launch_instance.yml -vvvv

This will launch the instance and you can also verify if the resources in the list of dynamic inventory got updated or not by running the following command

./ec2.py --list --profile personal --refresh-cache