Setting Up Lambda Functions with S3 Event Triggers

Lambda event triggers are extremely useful for automating serverless workflow, as they help trigger Lambda code/logic and have use cases from monitoring to processing online purchase orders and emailing receipts. In this lab, you’ll create a Lambda function from scratch and create an S3 event trigger to execute the Lambda logic.

Learning Objectives

Successfully complete this lab by achieving the following learning objectives:

Create an IAM Role for Lambda

Change to the directory where the necessary files are located:

cd exercise_files/Section4-AppLayer/Lab1-LambdaS3EventTrigger/

Create an IAM role for Lambda using the AWS IAM CLI command:

aws iam create-role --role-name LambdaIAMRole --description "Lambda Role" --assume-role-policy-document file://lambda_assume_role_policy.json

In the output under "Arn", copy the role ARN and paste it into a text file for later use.

Create a Policy for the Lambda Function and Attach It to Role

Create an IAM policy:

aws iam create-policy --policy-name LambdaRolePolicy --policy-document file://lambda_execution_policy.json

In the output under "Arn", copy the policy ARN for use in the next set of commands.
Attach the policy to the role, replacing <POLICY_ARN> with the ARN previously copied:
```
aws iam attach-role-policy --role-name "LambdaIAMRole" --policy-arn <POLICY_ARN>
```

Create an SNS Topic and Subscribe Your Email Address to It

Create an SNS topic:

aws sns create-topic --name LambdaTopic --region us-east-1

In the output under "TopicArn", copy the topic ARN for use in the next set of commands.
Subscribe an endpoint (e.g., email address) to your topic, replacing <TOPIC_ARN> with the previously copied ARN and <EMAIL_ADDRESS> with your own email:
```
aws sns subscribe --protocol "email" --topic-arn <TOPIC_ARN> --notification-endpoint <EMAIL_ADDRESS> --region us-east-1
```
You should receive the status message "SubscriptionArn": "pending confirmation".
To confirm the subscription, access the email previously used, open the SNS email, and click click Confirm subscription.

Modify the Lambda Function with the SNS Topic ARN and Zip It into a Lambda Deployment Package

Open the lambda_function.py file:
```
vim lambda_function.py
```

To enable sending SNS notifications, uncomment the line client = boto3.client('sns') and the section below:

response = client.publish(
TopicArn='<SNS-TOPIC-ARN>',
Message= payload_str,
Subject='My Lambda S3 event')

In TopicArn, replace <SNS-TOPIC-ARN> with the topic ARN previously copied.
To save and exit the file, press ESC, type :wq, and press Enter.

Zip the file into a deployment package:

zip lambda_function.zip lambda_function.py

Create a Lambda Function

Create a Lambda function, replacing <ROLE_ARN> with the role ARN previously copied:

aws lambda create-function --memory-size 128 --function-name my-lambda --runtime python3.7 --handler lambda_function.lambda_handler --zip-file fileb://lambda_function.zip --role <ROLE_ARN>

In the output under "FunctionArn", copy the function ARN to a text file for later use.

Add Lambda Permission for the S3 Service to Invoke the Function

Add Lambda permission, replacing <ARN_S3_BUCKET> with the ARN of the S3 bucket provided on the lab credentials page:

aws lambda add-permission --action lambda:InvokeFunction --principal s3.amazonaws.com --statement-id LabS3Trigger --function-name my-lambda --source-arn "<ARN_S3_BUCKET>"

Enable and Add Notification Configuration to the S3 Bucket

Open the bucket-trigger-notification.json file:
```
vim bucket-trigger-notification.json
```
In the output under "LambdaFunctionArn", delete the existing text and replace it with the function ARN previously copied into a text file:
```
"LambdaFunctionArn": "<FUNCTION_ARN>"
```
To save and exit the file, press ESC, type :wq, and press Enter.
Enable the notification configuration on the S3 website bucket, replacing <S3_BUCKET_NAME> with the bucket name provided on the lab credentials page:
```
aws s3api put-bucket-notification-configuration --bucket <S3_BUCKET_NAME> --notification-configuration file://bucket-trigger-notification.json
```

Verify Configuration by Uploading a File to the Provided S3 Bucket

Upload a file to the bucket, replacing <S3_BUCKET_NAME> with the bucket name provided on the lab credentials page:
```
aws s3 cp lambda_function.py s3://<S3_BUCKET_NAME>
```
Once successfully uploaded, check your email.
You should receive a notification email with details of the file uploaded to the S3 bucket.

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Setting Up Lambda Functions with S3 Event Triggers

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