AWS Lambda Exercise Challenge

Implementation Steps

Step 1: Create an S3 Bucket

1. Navigate to the AWS S3 Console: Open the AWS Management Console and select S3 from the Services menu.
2. Create a New Bucket: Click on the Create bucket button, provide a unique bucket name (e.g., word-count-bucket-as), choose a region, and then click Create bucket.

Step 2: Create an SNS Topic and Subscription

1. Navigate to the AWS SNS Console: Open the AWS Management Console and select SNS from the Services menu.
2. Create a Topic: Click on the Create topic button, choose Standard, provide a topic name (e.g., WordCountTopic), and click Create topic.
3. Create a Subscription: Click on the Create subscription button, select Email as the protocol, enter your email address as the endpoint, and click Create subscription. Confirm the subscription via the confirmation email sent to your inbox.

Step 3: Develop the Lambda Function

1. Navigate to the AWS Lambda Console: Open the AWS Management Console and select Lambda from the Services menu.
2. Create a New Function: Click on the Create function button, choose Author from scratch, provide a function name (e.g., WordCountFunction), select Python 3.8 as the runtime, choose an existing role with necessary permissions (e.g., LambdaAccessRole), and click Create function.
3. Update the Function Code:

Replace the default code with the following:

import json
import boto3
import logging
import urllib.parse

# Set up logging
logger = logging.getLogger()
logger.setLevel(logging.INFO)

def lambda_handler(event, context):
    logger.info('Event: %s', json.dumps(event))
    
    s3 = boto3.client('s3')
    sns = boto3.client('sns')
    
    try:
        # Get the bucket name and file name from the event
        bucket_name = event['Records'][0]['s3']['bucket']['name']
        file_name = event['Records'][0]['s3']['object']['key']
        
        # URL decode the file name
        file_name = urllib.parse.unquote_plus(file_name)
        
        logger.info('Bucket name: %s', bucket_name)
        logger.info('File name: %s', file_name)
        
        # Retrieve the file content from S3
        file_content = s3.get_object(Bucket=bucket_name, Key=file_name)['Body'].read().decode('utf-8')
        
        # Count the number of words in the file
        word_count = len(file_content.split())
        
        logger.info('Word count: %d', word_count)
        
        # Prepare the result message
        result_message = f"The word count in the {file_name} file is {word_count}."
        
        # Publish the result message to the SNS topic
        sns_topic_arn = 'arn:aws:sns:us-west-2:671579200908:WordCountTopic'
        sns.publish(TopicArn=sns_topic_arn, Message=result_message, Subject='Word Count Result')
        
        logger.info('Result message: %s', result_message)
        
        return {
            'statusCode': 200,
            'body': json.dumps(result_message)
        }
    except Exception as e:
        logger.error("Error processing file: %s", e)
        raise e

Deploy the Function: Click the Deploy button to save and apply the changes.

Step 4: Configure S3 Event Notification

1. Navigate to the S3 Console: Open the S3 console and select your bucket (word-count-bucket-as).
2. Set Up Event Notification:
   • Go to the Properties tab.
   • Scroll down to the Event notifications section and click Create event notification.
   • Provide an event name (e.g., WordCountEvent), select All object create events, specify the suffix .txt, choose Lambda function as the destination, and select the WordCountFunction.

Step 5: Troubleshooting and Issue Resolution

Despite following the above steps, I encountered some issues that required troubleshooting:

Older Version of Python Installed:

• Issue: Initially, I had an older version of Python (3.1.4) installed locally, which led to compatibility issues with AWS Lambda.
• Resolution: I updated the Lambda function code to use a more recent version of Python (3.8) to ensure compatibility with AWS Lambda and its libraries.

NoSuchKey Error:

• Issue: The Lambda function was timing out and logging a NoSuchKey error, indicating that the specified key (file name) did not exist.
• Resolution: The file name had spaces that were being URL-encoded as + or %20 in the S3 event. I updated the Lambda function code to handle URL-decoding using urllib.parse.unquote_plus(file_name). This resolved the issue.

Lambda Function Timeout:

• Issue: The Lambda function was timing out during execution.
• Resolution: I increased the function timeout to 5 minutes (0 minutes 5 seconds) in the General configuration section of the Lambda function settings.

Subscription Confirmation:

• Issue: I did not initially receive the SNS notifications.
• Resolution: I ensured that the email subscription to the SNS topic was confirmed by clicking the confirmation link in the email.

Successful Execution

After making these adjustments and deploying the updated Lambda function code, I uploaded a sample text file to the S3 bucket and successfully received the word count email notification from SNS.