01.Create Lambda

AWS Lambda is a service that runs your code only when something triggers it, you don’t manage servers.

Lambda part

1. Function code
   • Your Python file + lambda_handler(event, context)
   • This is the logic (compute bucket size, write DynamoDB, make plot…)
2. Runtime
   • The language environment Lambda provides (Python 3.11, Node.js, Java…)
   • Determines what built-in libraries are available
3. Trigger (Event source)
   • What causes Lambda to run
   • Examples: S3 upload/delete, API Gateway request, EventBridge schedule
4. Execution role (IAM Role)
   • Permissions for your Lambda to call AWS services
   • Example: allow s3:ListBucket, dynamodb:PutItem, CloudWatch Logs
5. Configuration
   • Memory, timeout, environment variables, architecture (x86_64/arm64)
   • Example: TABLE_NAME, BUCKET_NAME, TIME_WINDOW_SECONDS
6. Layers (optional)
   • Extra libraries or shared code
   • Example: matplotlib layer for plotting
7. Logging/Monitoring (CloudWatch)
   • Where print() output goes
   • Used by TAs to verify it ran and debug errors

boto3 create Lambda compulsory part

• Function Name
• Runtime
  • language environment:python
• Role
  • Lambda must assume an execution role
  • e.g., arn:aws:iam::<account-id>:role/<role-name>
• Handler
  • Entry point, tells Lambda which Python file and which function to call when the Lambda is invoked.
  • format: <file_name>.<function_name>
• Code

Manual setting

• Step1: Create Lambda
• Step2: Create Trigger
• Step3: Create Code source
• Step4: Grant the Lambda

Step1: Create Lambda

Step2: Create Trigger

Step3: Create Code source

Step4: Grant the Lambda Role Access to S3 and DynamoDB

{
	"Version": "2012-10-17",
	"Statement": [
		{
			"Sid": "AllowListBucket",
			"Effect": "Allow",
			"Action": [
				"s3:ListBucket"
			],
			"Resource": "arn:aws:s3:::assign2-test-bucket-alan"
		},
		{
			"Sid": "AllowPutItemToDDB",
			"Effect": "Allow",
			"Action": [
				"dynamodb:PutItem"
			],
			"Resource": "arn:aws:dynamodb:us-west-1:*:table/S3-object-size-history"
		}
	]
}