I made sure all the configurations were ok and that the My Inventory had some hosts in it, I even scheduled to update every 5 min and still the /tmp/autoscale.log file in the actual instances reports a 400, no hosts found. Even when I do it manually.

`curl -k -s -i --data host_config_key=My-key_here https://FQDN/api/v1/job_templates/759/callback/
HTTP/1.1 400 BAD REQUEST
Date: Tue, 03 May 2016 03:01:03 GMT
Server: Apache/2.4.6 (Red Hat Enterprise Linux) OpenSSL/1.0.1e-fips mod_wsgi/3.4 Python/2.7.5
Vary: Accept,Cookie
Allow: GET, POST, HEAD, OPTIONS
X-API-Time: 0.042s
Content-Length: 43
Connection: close
Content-Type: application/json

{"msg": "No matching host could be found!"}`

I am getting the following errors when trying to attach autoscaling group to elb
just following same example as the one you have
did you guys test this code?

the error is below

"msg": "Failed to create Autoscaling Group: BotoServerError: 400 Bad Request\n<ErrorResponse xmlns=\"http://autoscaling.amazonaws.com/doc/2011-01-01/\">\n <Error>\n <Type>Sender</Type>\n <Code>ValidationError</Code>\n <Message>Provided Load Balancers may not be valid. Please ensure they exist and try again.</Message>\n </Error>\n <RequestId>bc6fc38e-8dfe-11e7-bbae-d56fd34454</RequestId>\n</ErrorResponse>\n"

checked and the loadbalancer were created and exist and they are fine but i have no idea why the autoscaling group is not able to find them

roles/infra/tasks/main.yml

- name: create scale down alarm
  ec2_metric_alarm:
    state: present
    region: "{{ region }}"
    name: "cpu-low"
    metric: CPUUtilization
    namespace: "AWS/EC2"
    statistic: Average
    comparison: "<="
    threshold: 5.0
    period: 300
    evaluation_periods: 3
    unit: "Percent"
    description: "This will alarm when cpu usage average is lower than 5% for 15 minutes "
    dimensions:
      AutoScalingGroupName: "{{ app_name }}"
    alarm_actions:
    - "{{ scale_down_policy.arn }}"
  tags: alarm

Attempting to run this playbook as-is results in the following error:

argument threshold is of invalid type: <type 'int'>, required: float

This is due to the threshold variable in the "create scale down alarm" play being cast automatically as "int" instead of float. This can be resolved by ensuring the value of threshold is in decimal form, i.e. "5.0"

Most of the images are missing in the blog post. Could you update the image urls? Its hard to figure out whats going on without them.

You have <= 90.0 % CPU usage for scale up which is basically ALWAYS true which will keep the ASG spinning instances up unnecessarily.