handler.py

from __future__ import print_function

import json
import boto3
import os

def lambda_handler(event, context):
    instance_id = event.get("detail", {}).get("instance-id", "")
    
    if instance_id == "":
        print("Empty instance id")
        
        return
    
    print("Instance id: " + instance_id)
    
    ec2 = boto3.resource("ec2")
    
    instance = ec2.Instance(instance_id)
    
    name = ""
    
    for tag in instance.tags:
        if tag.get("Key", "") == "Name":
            name = tag.get("Value")

    warn_statuses = [
        "stopping",
        "shutting-down"
    ]
    
    state = event.get("detail", {}).get("state", "")
    
    if state in warn_statuses:
        sns = boto3.client("sns")
        
        message = {
            "event_type": "trigger",
            "description": "Instance %s is %s" % (instance_id, state),
            "details": {
                "instance_id": instance_id,
                "name": name
            }
        }
        
        sns.publish(
            TopicArn=os.environ.get("SNS_TOPIC", ""),
            Message=json.dumps(message))