STEP-BY-STEP GUIDE: Lambda + CRR + EC2 Control + SNS (Email)

Create an SNS Topic for Email Alerts

1. Go to AWS Console > SNS > Topics
2. Click Create topic
   • Type: Standard
   • Name: AlertTopic
3. Click Create
4. Under Subscriptions, click Create subscription
   • Protocol: Email
   • Endpoint: your email address
5. Check your email inbox and confirm the subscription

IAM Role for Lambda

You’ll need a role with permissions to control EC2, publish to SNS, and read from S3.

1. Go to IAM > Roles > Create Role
2. Select AWS Service > Lambda
3. Attach policies:
   • AmazonEC2FullAccess
   • AmazonSNSFullAccess
   • AmazonS3ReadOnlyAccess
4. Name the role: LambdaAutomationRole

Enable Cross-Region Replication (CRR)

1. Go to S3 > Create two buckets:
   • Source: my-source-bucket-123
   • Destination: my-destination-bucket-123
   • Must be in different AWS regions
2. Enable versioning on both buckets.
3. In the source bucket, go to Management > Replication rules
   • Add a rule:
     • Source: Entire bucket
     • Destination: Your destination bucket
     • IAM Role: Create one or use an existing S3 replication role
4. Save the rule — CRR is now enabled.

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Create Lambda for S3 CRR Monitoring

1. Go to Lambda > Create Function
   • Name: MonitorCRR
   • Runtime: Python 3.10
   • Permissions: Choose Use existing role > Select LambdaAutomationRole
2. Paste the code:

import boto3
import json

def lambda_handler(event, context):
    s3 = boto3.client('s3')
    sns = boto3.client('sns')

    for record in event['Records']:
        bucket = record['s3']['bucket']['name']
        key = record['s3']['object']['key']

        message = f"New object '{key}' added to bucket '{bucket}'. Check replication status."

        sns.publish(
            TopicArn='arn:aws:sns:your-region:your-account-id:AlertTopic',
            Message=message,
            Subject='[CRR Monitor] New S3 Upload'
        )

    return {
        'statusCode': 200,
        'body': json.dumps('CRR notification sent.')
    }

Click Deploy

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Connect S3 to Trigger Lambda

1. Go to S3 > Your source bucket > Properties
2. Scroll to Event Notifications
3. Click Create Event Notification
   • Name: NewUploadTrigger
   • Event type: All object create events
   • Destination: Lambda function > Choose MonitorCRR

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Create Lambda to Start/Stop EC2 with SNS

1. Go to Lambda > Create Function

   • Name: EC2ControlNotify
   • Runtime: Python 3.10
   • Role: Use LambdaAutomationRole

2. Paste this code:
   

import boto3

ec2 = boto3.client('ec2')
sns = boto3.client('sns')

def lambda_handler(event, context):
    instance_id = 'i-xxxxxxxxxxxxxxxxx'  # Replace with your EC2 instance ID
    action = 'start'  # or 'stop'

    if action == 'start':
        ec2.start_instances(InstanceIds=[instance_id])
        message = f"Started EC2 instance {instance_id}"
    else:
        ec2.stop_instances(InstanceIds=[instance_id])
        message = f"Stopped EC2 instance {instance_id}"

    sns.publish(
        TopicArn='arn:aws:sns:your-region:your-account-id:AlertTopic',
        Message=message,
        Subject=f'[EC2 Control] {action.upper()} action performed'
    )

    return {'status': 'success', 'message': message}

Click Deploy

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(Optional) Trigger EC2 Lambda Automatically

If you want to start/stop EC2 on schedule:

1. Go to CloudWatch > Rules > Create rule
2. Event Source: Schedule
   • Example: cron(0 18 * * ? *) for 6 PM UTC daily
3. Target: Lambda function > Choose EC2ControlNotify

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Test Everything

• Upload an object to the source S3 bucket → Check your email for CRR alert.
• Run EC2 Lambda manually → Instance should start/stop and email should arrive.
• Check CloudWatch Logs for debugging.

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Bonus Tip: Secure Your Setup

• Use environment variables in Lambda to avoid hardcoding instance IDs or SNS ARNs.
• Add logging and error handling.
• Use CloudTrail to audit changes.