Tutorial: How to Create an AWS Lambda Function to save file to an S3 Bucket

Introduction:
AWS Lambda is a serverless computing service that allows you to run your code without provisioning or managing servers. One common use case is to save files to an Amazon S3 bucket using a Lambda function. In this tutorial, we’ll walk through the steps to create an AWS Lambda function in Python 3.10 and grant it the necessary permissions to save files to an S3 bucket.

Steps:

1. Create an S3 Bucket:
— Log in to the AWS Management Console and open the S3 service.
— Click on “Create bucket” and provide a unique bucket name and region.
— Leave the default configuration options and create the bucket.

2. Create an IAM Role:
— Open the IAM service in the AWS Management Console.
— Click on “Roles” and then “Create role”.
— Select the “AWS Lambda” service as the trusted entity.
— Attach the “AmazonS3FullAccess” policy to grant necessary S3 permissions.
— Name the role and create it.

3. Create an AWS Lambda Function:
— Open the Lambda service in the AWS Management Console.
— Click on “Create function” and choose the “Author from scratch” option.
— Provide a name and select Python 3.10 as the runtime.
— Under “Permissions”, choose “Use an existing role” and select the IAM role created earlier.
— Click on “Create function” to create the Lambda function.

4. Configure the Lambda Function:
— In the function code section, replace the default code with the following:

import boto3 

def lambda_handler(event, context): 
  bucket_name = 'YOUR_BUCKET_NAME' 
  file_name = 'file_name.txt' 
  file_content = 'This is the content of the file.' 

  s3 = boto3.client('s3') 
  s3.put_object(Body=file_content, Bucket=bucket_name, Key=file_name) 
  return { 
      'statusCode': 200, 
      'body': 'File uploaded successfully.' 
  }

— Replace YOUR_BUCKET_NAME with name of your S3 bucket (step 1)

5. Configure and Test the Lambda Function:
— Click on the “Test” button in the Lambda console.
— Select “Configure test events” and click on “Create new test event”.
— Provide a name for the test event, such as “S3UploadTestEvent”.
— Keep the default event JSON as it is.
— Click on “Save” at the bottom of the page to save the test event.
— Select the newly created test event from the drop-down menu next to “Test” button
— Click on “Test” to execute the Lambda function with the configured test event.

sucessful execution of our Lambda function

By configuring a test event, you can simulate the Lambda function’s execution with specific event data. This allows you to verify the functionality of your Lambda function and ensure that it can successfully save files to the S3 bucket.

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