Deploy Lambda#

AWS Lambda handlers in Python are just functions that:

  • Accept an event (input data)
  • Return a response object

In other words, we don’t worry about the runtime, the server, or even any sort of HTTP library. We just write a function that accepts an event object and returns a response object.

The process to create a new Lambda function is simple:

  1. Create an IAM role that gives Lambda permission to write logs to CloudWatch
  2. Create the Lambda function itself
  3. Paste the handler code and deploy

Assignment#

Create and deploy patientping-ip-function with role patientping-lambda-role by pasting Python code in the AWS Console.

Cost check: Lambda functions themselves don’t cost anything when not running. Storage for the deployment package costs about $0.0000000034 per GB per hour (basically free for a small function like this).

  1. In the AWS Console, navigate to IAM → Roles, then create a role:
    • Trusted entity type: AWS service
    • Use case: Lambda
    • Permissions policy: AWSLambdaBasicExecutionRole
    • Role name: patientping-lambda-role
  2. In the AWS Console, navigate to Lambda and click Create function.
  3. Choose Author from scratch, then set:
    • Function name: patientping-ip-function
    • Runtime: Python 3.14 (or latest available Python 3.x runtime)
    • Under Permissions, select the existing patientping-lambda-role role (you may need to expand More settings or look for a Custom execution role option)
    • Leave all additional configurations as default and click Create function.
  4. In the function’s Code tab, replace the default code in lambda_function.py with:
def lambda_handler(event, context):
    request_context = event.get("requestContext", {})
    identity = request_context.get("identity", {})
    ip_address = identity.get("sourceIp")
    if not ip_address:
        headers = event.get("headers", {})
        ip_address = headers.get("X-Forwarded-For") or headers.get("x-forwarded-for")
    if not ip_address:
        ip_address = "unknown"
    print(f"Received IP: {ip_address}")
    return {
        "statusCode": 200,
        "headers": {
            "Content-Type": "text/plain",
        },
        "body": f"Your IP address is: {ip_address}",
    }
  1. Keep the default handler lambda_function.lambda_handler, then click Deploy.

If you prefer CLI + local zip:

cat > lambda_function.py <<'PY'
def lambda_handler(event, context):
    request_context = event.get("requestContext", {})
    identity = request_context.get("identity", {})
    ip_address = identity.get("sourceIp")
    if not ip_address:
        headers = event.get("headers", {})
        ip_address = headers.get("X-Forwarded-For") or headers.get("x-forwarded-for")
    if not ip_address:
        ip_address = "unknown"
    print(f"Received IP: {ip_address}")
    return {
        "statusCode": 200,
        "headers": {
            "Content-Type": "text/plain",
        },
        "body": ip_address,
    }
PY

zip lambda-function.zip lambda_function.py
aws iam create-role --role-name patientping-lambda-role --assume-role-policy-document '{"Version":"2012-10-17","Statement":[{"Effect":"Allow","Principal":{"Service":"lambda.amazonaws.com"},"Action":"sts:AssumeRole"}]}'
aws iam attach-role-policy --role-name patientping-lambda-role --policy-arn arn:aws:iam::aws:policy/service-role/AWSLambdaBasicExecutionRole
aws lambda create-function --function-name patientping-ip-function --runtime python3.12 --role arn:aws:iam::YOUR_ACCOUNT_ID:role/patientping-lambda-role --handler lambda_function.lambda_handler --zip-file fileb://lambda-function.zip

In the next lesson, we’ll test this function and learn how to update it.

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