https://medium.com/p/b7c216292b5f

playbook.yml

- name: "Create Launch Configuration, ELB, Auto-Scaling group and rolling update of AMI"
  hosts: localhost
  tags:
    - aws
  vars:
    - AMI: ami-xxxxxx
    - region: us-east-1
    - app: "coolapp"
    - security_groups:
        - sg-xxxxx
     - subnets:
        - subnet-xxxxx
    - new_lc: "{{app}}-{{ AMI }}"
    - min_instances: 2
    - desired_instances: 2
    - max_instances: 4
    - instances_type: t2.small
    - iam_profile: "your_instance_iam_profile"
  tasks:

    - name: Get all the Auto Scaling Groups from awscli
      shell: aws autoscaling describe-auto-scaling-groups
      register: asg_output

    - name: Get all the instances handled by an Auto Scalling Groups from awscli
      shell: aws autoscaling describe-auto-scaling-instances
      register: asg_instances_output

    - name: Initialize the current Launch Configration and Auto Scaling Group to Null
      set_fact:
        current_lc: null # this necessary for the first update when the ASG doesn't exist
        current_asg: null
        running_instances: 0

    - name: Find all the matching Auto Scaling Group
      set_fact:
        asg_list: "{{ (asg_output.stdout
                        | from_json)['AutoScalingGroups']
                        | selectattr('AutoScalingGroupName', 'equalto', app)
                        | list }}"

    - name: Find current Auto Scaling Group and Launch Configuration
      set_fact:
        current_asg: "{{ (asg_list | first)['AutoScalingGroupName'] }}"
        current_lc: "{{ (asg_list | first)['LaunchConfigurationName'] }}"
      when: asg_list | length > 0   

    - name: Check if Launch Configuration needs to be updated
      set_fact:
         update_lc: "{{ new_lc != current_lc }}"

    - name: Get Running instances in the Current Auto Scaling Group
      set_fact:
         running_instances: "{{ (asg_instances_output.stdout
                                 | from_json)['AutoScalingInstances']
                                 | selectattr('AutoScalingGroupName', 'equalto', current_asg)
                                 | list
                                 | length }}"
      when: current_asg and update_lc

    - name: Update desired instances if more instances are currently running
      set_fact:
         desired_instances: "{{ running_instances }}"
      when: running_instances > desired_instances and update_lc

    - name: Describe Launch configuration
      shell: aws autoscaling describe-auto-scaling-groups
      register: asg_output

    - name: Create or Update Elastic Load Balancer
      ec2_elb_lb:
        region: us-east-1
        name: "{{ app }}"
        state: present
        connection_draining_timeout: 120
        scheme: internal
        security_group_ids: "{{ security_groups }}"
        subnets: "{{ subnets }}"
        listeners:
          - protocol: http
            load_balancer_port: 80
            instance_port: 80
        health_check:
          ping_protocol: tcp
          ping_port: 80
          response_timeout: 29
          interval: 30
          unhealthy_threshold: 4
          healthy_threshold: 2
    - name: Create Launch Configuration
      ec2_lc:
        name: "{{ new_lc }}"
        region: "{{ region }}"
        image_id: "{{ AMI }}"
        security_groups: "{{ security_groups }}"
        instance_type: "{{ instances_type }}"
        instance_profile_name: "{{ iam_profile }}"
      when: update_lc
    - name: Create or Update Auto Scalling Group
      ec2_asg:
        name: "{{ app }}"
        region: "{{ region }}"
        launch_config_name: "{{ new_lc }}"
        health_check_period: 300
        health_check_type: ELB
        desired_capacity: "{{ desired_instances }}"
        min_size: 2
        max_size: 10
        vpc_zone_identifier: "{{ vpc_subnets.subnets|map(attribute='id')|list }}"
        load_balancers: "{{ app }}"
        replace_all_instances: true
        wait_for_instances: true
      when: update_lc
    - name: Delete Old Launch Configuration
      ec2_lc:
        name: "{{current_lc}}"
        state: absent
        region: "{{ region }}"
      when: update_lc and current_lc # current_lc is now the old launch config