AWS Lambda Function to Run SSM Document on Tagged Instances

This repository contains an AWS Lambda function that triggers an SSM document (including document yaml) on EC2 instances based on key-value tags.

Script Explanation

Initialize boto3 clients

We create clients for both SSM and EC2 services.

Specify Parameters

Define the SSM document name and the key-value tag pair to filter instances.

Describe Instances

Use the describe_instances method with a filter to get instances matching the specified tags.

Extract Instance IDs

Iterate over the response to extract instance IDs.

Check Instance IDs

Return a 404 response if no instances are found.

Send SSM Command

Trigger the SSM document on the found instances using send_command.

Return Response

Return the response details or handle exceptions and return error messages.

Lambda Function Code

import json
import boto3
from datetime import datetime
from decimal import Decimal

# Custom JSON Encoder
class CustomEncoder(json.JSONEncoder):
    def default(self, obj):
        if isinstance(obj, datetime):
            return obj.isoformat()
        elif isinstance(obj, Decimal):
            return float(obj)
        return json.JSONEncoder.default(self, obj)

def lambda_handler(event, context):
    # Initialize boto3 clients
    ssm_client = boto3.client('ssm')
    ec2_client = boto3.client('ec2')
    
    # Parameters
    document_name = 'Disk-cleanup'  # Using a standard SSM document
    tag_key = 'Environment'  # Replace with your tag key
    tag_value = 'Production'  # Replace with your tag value
    
    try:
        # Describe instances with the specified tag key-value pair
        response = ec2_client.describe_instances(
            Filters=[
                {
                    'Name': f'tag:{tag_key}',
                    'Values': [tag_value]
                }
            ]
        )
        
        # Extract instance IDs
        instance_ids = []
        for reservation in response['Reservations']:
            for instance in reservation['Instances']:
                instance_ids.append(instance['InstanceId'])
        
        if not instance_ids:
            return {
                'statusCode': 404,
                'body': json.dumps({'error': 'No instances found with the specified tags'}, cls=CustomEncoder)
            }
        
        # Trigger the SSM Run Command
        ssm_response = ssm_client.send_command(
            InstanceIds=instance_ids,
            DocumentName=document_name
        )
        
        # Return the command ID and other response details
        return {
            'statusCode': 200,
            'body': json.dumps(ssm_response, cls=CustomEncoder)
        }
    
    except Exception as e:
        # Handle exceptions and return the error message
        return {
            'statusCode': 500,
            'body': json.dumps({'error': str(e)}, cls=CustomEncoder)
        }