Session Management > Preparation > Create Lambda function

Create Lambda function

In this step, we will create an AWS Lambda Function, fully configuring elements such as: source code, access permissions (IAM Role), environment variables, and testing the function to log data into DynamoDB.

Goals:

Create a Lambda function to handle API logic..
Configure an IAM Role that grants write permissions.
Add environment variables to store MongoDB connection info (URI, DB name, collection).
Write and directly deploy the handler code.

Steps:

Access the Lambda Service:

Go to AWS Console: AWS console
Search for “Lambda” in the search bar and select AWS Lambda service.

Create a Lambda function:

Click “Create function”.
Choose ọn Author from scratch.
Enter the details:
- Function name: GetVisitor.
- Runtime: Python 3.11.
Click Create Function.

Deploy the source code

Paste the following code into the editor.

import json
import boto3
from datetime import datetime
import urllib.request

dynamodb = boto3.resource('dynamodb')
table = dynamodb.Table('WebsiteVisitors')

def get_location(ip):
    try:
        with urllib.request.urlopen(f"http://ip-api.com/json/{ip}") as url:
            data = json.loads(url.read().decode())
            return {
                'country': data.get('country'),
                'region': data.get('regionName'),
                'city': data.get('city'),
                'lat': data.get('lat'),
                'lon': data.get('lon'),
            }
    except:
        return {}


def lambda_handler(event, context):
    headers = event.get('headers', {})
    request_context = event.get('requestContext', {})

    ip = request_context.get('identity', {}).get('sourceIp', 'unknown')
    user_agent = headers.get('User-Agent', headers.get('user-agent', 'unknown'))
    visit_time = str(datetime.utcnow())
    location = get_location(ip)
    key = f"{ip}_{user_agent}" if ip != 'unknown' else 'unknown'

    try:
        response = table.get_item(Key={'user_key': key})
        item = response.get('Item', {})

        if item:
            item['count'] = int(item.get('count', 0)) + 1
            item['last_visit'] = visit_time
        else:
            item = {
                'user_key': key,
                'ip': ip,
                'user_agent': user_agent,
                'count': 1,
                'first_visit': visit_time,
                'last_visit': visit_time,
                'country': location.get('country'),
                'city': location.get('city'),
                'lat': str(location.get('lat')),
                'lon': str(location.get('lon'))
            }

        table.put_item(Item=item)

        return {
            "statusCode": 200,
            "headers": {
                "Content-Type": "application/json"
            },
            "body": json.dumps({
                "message": "Visitor tracked successfully",
                "user_key": key,
                "count": item['count']
            })
        }


        cloudwatch = boto3.client('cloudwatch')

        cloudwatch.put_metric_data(
            Namespace='VisitorAnalytics',
            MetricData=[
                {
                    'MetricName': 'TotalVisits',
                    'Dimensions': [{'Name': 'Country', 'Value': location.get('country', 'Unknown')}],
                    'Value': 1,
                    'Unit': 'Count'
                }
            ]
        )


    except Exception as e:
        print(f"Error: {e}")
        return {
            "statusCode": 500,
            "headers": {
                "Content-Type": "application/json"
            },
            "body": json.dumps({
                "message": "Error processing request",
                "error": str(e)
            })
        }

Then click Deloy.

lambda

Add Environment Variables

Go to Configuration tab, then click Environment variables.

lambda

Click Edit and click Add eviromment variable

lambda

Add the following key-value pair::
- Key: WebsiteVisitors
- Value: WebsiteVisitors

lambda

Click save to completed.

Update IAM Role

Go to Configuration tab, then chosse Environment variables.
Click on Role name.

lambda

Once on the IAM Role page, click Add permissions, then choose Attach policies.

lambda

Select the policy named: AmazonDynamoDBFullAccess
Then choose Add permission.

lambda

Now repeat the steps above to create another Lambda function::

Function name: createUser.
Runtime: Python 3.11.
Deploy the following code.

import json
import uuid
from datetime import datetime
import boto3

dynamodb = boto3.resource('dynamodb')
table = dynamodb.Table('Users')
cloudwatch = boto3.client('cloudwatch')

def put_custom_metric(metric_name):
    cloudwatch.put_metric_data(
        Namespace='YourApp/Lambda',
        MetricData=[{
            'MetricName': metric_name,
            'Value': 1,
            'Unit': 'Count'
        }]
    )

def lambda_handler(event, context):
    print("Received event:", json.dumps(event))

    try:
        body = json.loads(event.get('body', '{}'))
        name = body.get('name')
        email = body.get('email')

        if not name or not email:
            # Gửi metric cho lỗi Client
            put_custom_metric('ClientErrors')

            return {
                "statusCode": 400,
                "body": json.dumps({"message": "Name and email are required"})
            }

        user = {
            'user_id': str(uuid.uuid4()),
            'name': name,
            'email': email,
            'created_at': datetime.utcnow().isoformat()
        }

        table.put_item(Item=user)

        return {
            "statusCode": 201,
            "body": json.dumps({
                "message": "User created successfully",
                "user": user
            })
        }

    except Exception as e:
        print("Error:", str(e))

        # Gửi metric cho lỗi Server
        put_custom_metric('ServerErrors')

        return {
            "statusCode": 500,
            "body": json.dumps({
                "message": "Internal server error",
                "error": str(e)
            })
        }

Repeat the IAM Role configuration step.

Next, we will create the API Gateways.