Determine if the instances in an autoscaling group are InService in its ELBs attached to that group. Used in conjunction with Ansible's ec2_asg module.

elb-health-check.py

#!/usr/bin/env python
"""Determine if the instances in an autoscaling group are InService in its ELBs
attached to that group.
"""

import sys
import boto.ec2.elb
import boto.ec2.autoscale
import argparse

parser = argparse.ArgumentParser(description='Given an ASG, check if its instances are InService in an ELB')
parser.add_argument('-a', '--autoscale-group',
                    required=True,
                    help='Name of an autoscale group')
parser.add_argument('-r', '--region',
                    required=True,
                    help='AWS region')
parser.add_argument('-k', '--access-key',
                    required=True,
                    help='AWS Access Key')
parser.add_argument('-s', '--secret-key',
                    required=True,
                    help='AWS Secret Key')
args = parser.parse_args()

AWS_ACCESS_KEY = args.access_key
AWS_SECRET_KEY = args.secret_key
AWS_REGION = args.region
AWS_ASG = args.autoscale_group


conn_as = boto.ec2.autoscale.connect_to_region(AWS_REGION, aws_access_key_id=AWS_ACCESS_KEY, aws_secret_access_key=AWS_SECRET_KEY)
asg = conn_as.get_all_groups(names=[AWS_ASG])[0]
if asg.health_check_type != "ELB":
    sys.exit("ASG does not use ELB health checks. Quitting.")
instances = [i.instance_id for i in asg.instances]
if len(instances) != asg.desired_capacity:
    sys.exit("Number of instances do not yet match desired capacity")

conn_elb = boto.ec2.elb.connect_to_region(AWS_REGION, aws_access_key_id=AWS_ACCESS_KEY, aws_secret_access_key=AWS_SECRET_KEY)
for lb in asg.load_balancers:
    for i in conn_elb.describe_instance_health(lb, instances=instances):
        if i.state != "InService":
            sys.exit("Instance {} is not InService")

gistfile1.txt

# Ansible play that uses this script
- name: wait for instances to become InService in the ELB
  shell: 'python "{{health_check_script}}" -r "{{region}}" -k "{{aws_access_key}}" -s "{{aws_secret_key}}" -a "{{service_name}}-{{env}}-{{docker_tag}}"'
  register: result
  until: result.rc == 0
  delay: 10
  retries: 120