[AWS Lab] Lambda – Environment Variables

In this lab, we will learn how to use environment variables in a Lambda function.

Overview

• S3
  • Create a bucket
  • Upload an image file
• Lambda – Function
  • Get the bucket name and the image name from environment variables
  • Retrieves the object properties
  • Python, boto3

1. S3 – Create a bucket

• Click “Create bucket”
  • Bucket name: unique name of your choice, such as “my-bucket-2022-12-31“
• Accept all defaults and click “Create bucket”
  • Note that the public access is disabled by default
• Click the bucket name you just created
• Click “Upload” and upload any image file

2. IAM – Setup the Lambda execution role

• Click “Roles” on the left pane
• Click “Create role“
• Trusted entity type
  • Select “AWS service“
• Use case
  • Select “Lambda“
• Add Permissions
  • Search “CloudWatchLogsFullAccess” and select it
  • Search “AmazonS3ReadOnlyAccess” and select it
• Name, review
  • Role name: “LambdaS3ExecutionRole“
• Click “Create role“

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Action": [
                "logs:*"
            ],
            "Effect": "Allow",
            "Resource": "*"
        }
    ]
}
{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": [
                "s3:Get*",
                "s3:List*",
                "s3-object-lambda:Get*",
                "s3-object-lambda:List*"
            ],
            "Resource": "*"
        }
    ]
}

3. Lambda – Create a Function

• Function Name: “GetS3Object“
• Runtime: Python 3.10
• Permissions – Change default execution role
  • Check “Use an existing role“
  • Select “LambdaS3ExecutionRole“
• Click “Create function“

4. Lambda – Function Code (Python)

• Type the following code
• Click “Deploy“

import json
import logging
import os
import boto3

logger = logging.getLogger()
logger.setLevel(logging.INFO)

client = boto3.client('s3')

def lambda_handler(event, context):
    bucketName = os.environ['BucketName']
    imageName = os.environ['FileName']
    logger.info(bucketName + ' ' + imageName)
 
    response = client.get_object(
        Bucket = bucketName,
        Key = imageName,
    )
    logger.info(response)

5. Lambda – Set the default environment variables

• Click the “Configuration” tab
• Click “Environment variables“
• Click “Edit“
• Click “Add environment variable”
  • Key: “BucketName”
  • Name: “{your bucket name}“
• Click “Add environment variable”
  • Key: “FileName“
  • Value: “{your file name}“

6. Lambda – Test

• Click the “Test” tab
  • Select “Create new event”
    • Event name: “LambdaEnvTest“
    • Accept all default settings
• Click “Save“
• Click “Test“

7. CouldWatch – Check the Lambda logs

1. On the Lambda function page, click the “Monitor” tab
2. Check some metrics on the page
3. Click the “View logs in the CloudWatch” button
4. On the CloudWatch page, click the “Log stream“
5. Check the logs