AWS Auto Scaling Group Clean Shutdown

asg_worker.py

import datetime
from time import sleep

import boto3
import requests

SPOT_URL = 'http://169.254.169.254/latest/meta-data/spot/instance-action'
ID_URL = 'http://169.254.169.254/latest/meta-data/instance-id'
EC2 = boto3.client('ec2')


def do_work():
    """ Do something meaningful """
    print(datetime.datetime.now())
    

def check_spot_shutdown():
    """
    Check instance metadata for spot shutdown
    Returns True if shutdown is signaled
    """
    response = request.get(SPOT_URL)
    if response.ok:
        return True
    return False
    
    
def check_asg_scale_in(instance_id=None):
    """
    Check instance tags for scale in shutdown
    Returns True if shutdown is signaled
    """
    if instance_id is None:
        response = request.get(ID_URL)
        if response.ok:
            instance_id = response.text
        else:
            raise ValueError('No instance_id')
    
    tags = EC2.describe_tags(Filters=[{'Name': 'resource-id',
                                       'Values': [instance_id]}])
    tags = {tag['Key']: tag['Value'] for tag in tags['Tags']}
    if 'asg_scale_in' in tags:
        asg_complete_kwargs = {'AutoScalingGroupName': tags['AutoScalingGroupName'],
                               'LifecycleHookName': tags['LifecycleHookName'],
                               'LifecycleActionToken': tags['LifecycleActionToken'],
                               'LifecycleActionResult': 'ABANDON',
                               'InstanceId': instance_id}
        # Signal shutdown
        return True, asg_complete_kwargs
    return False, {}


def main():
    running = True
    tags = {}
    while running:
        do_work()
        running &= check_spot_shutdown()
        asg_running, asg_complete = check_asg_scale_in()
        running &= asg_running
        sleep(10)
    
    if 'LifecycleActionToken' in asg_complete:
        client = boto3.client('autoscaling')
        client.complete_lifecycle_action(**asg_complete)
        
        
if __name__ == '__main__':
    main()

lambda.py

import json
import boto3

ec2 = boto3.client('ec2')

def lambda_handler(event, context):
    print(event)
    
    detail = event['detail']
    
    if 'TERMINATING' not in detail['LifecycleTransition']:
        print('Nothing to do')
        return
    
    tags = [{'Key': 'asg_scale_in', 'Value': 'SHUTDOWN'},
            {'Key': 'AutoScalingGroupName', 'Value': detail['AutoScalingGroupName']},
            {'Key': 'LifecycleHookName', 'Value': detail['LifecycleHookName']},
            {'Key': 'LifecycleActionToken', 'Value': detail['LifecycleActionToken']}]

    ec2.create_tags(Resources=[detail['EC2InstanceId']], Tags=tags)
    print('Added tags to instance {}'.format(detail['EC2InstanceId']))