Integrating AWS Lambda with Application Load Balancer

With the growing acceptance of the serverless architecture within businesses, AWS Lambda is a computing service that is being applied broadly for running functions without provisioning or managing servers. However, maintaining balance in the traffic reaching these Lambda functions is one critical factor that affects high availability and high efficiency. A simple yet seamless way to accomplish this is through integrating AWS Lambda with the Application Load Balancer (ALB) functionalities. This enables Lambda functions to directly service web requests; as such, this is an integration that assures scaling and performance as smoothly as possible.

In this article, we describe how to set up AWS Lambda for a serverless load-balancing service with an Application Load Balancer, continue with setup steps, and zoom in on the components related to integration with AWS Lambda. Further, we will see answers to some common questions about this integration.

Primary Terminologies

• Lambda: Lambda is a serverless compute service that lets you run your code without the need to provision or manage servers. It automatically scales with incoming traffic and charges for actual compute time, meaning you can always be sure you pay exactly for the resources spent running your functions and not just idle time.
• Application Load Balancer (ALB): A Layer-7 load balancer in the OSI model, working within HTTP/HTTPS requests' routing from sources to targets according to rules. ALBs support such features as host-based and path-based routing.
• Target Group: A collection of resources (a Lambda function, an EC2 instance, or a container) on which the load balancer sends requests, in this context, the Lambda functions are acting as the target group for the Application Load Balancer.
• Listener: The load balancer process that checks for incoming connection requests and then routes these requests to the target group based on defined rules
• Rule: A condition which further narrows down the definition of the way in which requests are to be sent to different groups of destinations, typically based on criteria such as URL paths or HTTP headers.

Step-by-Step Process for AWS Lambda and Application Load Balancer (ALB) Integration

Step 1: Create an AWS Lambda Function

Navigate to AWS Lambda Console:

• Open the AWS Management Console and search for Lambda in the services search bar.

Create a New Lambda Function:

• Click Create Function.

• Select Author from scratch.
• Enter a function name and select the desired runtime (e.g., Node.js, Python).

Configure Function Code:

• Write the code for your Lambda function, such as a simple handler that returns a JSON response.
• Example:

def lambda_handler(event, context):

return {

'statusCode': 200,

'body': 'Hello from Lambda!'

}

Step 2: Create an Application Load Balancer (ALB)

Search for Load Balancer

Choose Application Load Balancer:

• Select Application Load Balancer as the load balancer type.
• Configure the name, scheme (internet-facing or internal), and IP address type (IPv4).

Set Up Listeners and Availability Zones:

• Specify Listeners for HTTP or HTTPS (you can also configure SSL certificates for HTTPS traffic).
• Select the VPC and Availability Zones where the ALB will operate to ensure high availability.

Step 3: Create a Target Group for AWS Lambda

Navigate to Target Groups:

• Select Target Groups from the left menu and click Create target group.

Select Lambda as the Target Type:

• Choose Lambda as the target type.

Configure Target Group:

• Provide a name for the target group.

Select the Lambda function created earlier as the target.

Our Target group was successfully created

Step 3: Configure the Application Load Balancer to Route Traffic to Lambda

Navigate to ALB Settings:

• Return to the Load Balancer section in the EC2 console.
• Select your Application Load Balancer and go to the Listeners tab.

Create a Rule to Route Traffic:

• In the Listener tab, click View/edit rules and create a new rule.
• Define the routing rules based on conditions like HTTP methods or path-based routing.
• Example: Route traffic to the /api path to your Lambda function.

Here we see that new rule was created

Step 4: Test the Configuration

Access the ALB:

• After completing the setup, use the DNS name of the Application Load Balancer to access it.
• Open a browser or HTTP client (e.g., Postman) and send a request to the ALB.

Verify Lambda Execution:

• The request should be routed to the Lambda function, and the function will return the appropriate response.

• Example Response: "Hello from Lambda!"

Conclusion

The combination of AWS Lambda and Application Load Balancer provides a serverless, scalable, flexible, and cost-effective manner of load balancing. This setup makes the management of the spread of traffic look easy in such a manner that high availability is realized with optimized performance for serverless applications. With its routing capabilities, ALB sends incoming requests to multiple Lambda functions using rules—for example, path-based routing. This will allow the architecture to handle functions that are with Lambda, supporting auto-scaling and reducing the intricacy of managing infrastructures while maintaining a robust performance in web- and API-based workloads. This integration is an ideal fit for any organization desiring to build and scale serverless applications easily.