Multi-Tier AI Application Load Balancing with AWS ALB

Question

Pulumi · Accepted Answer

If you're building a multi-tier AI application on AWS and you want to use an Application Load Balancer (ALB) to distribute traffic across your application's tiers, it's essential to set up your infrastructure to handle incoming traffic and route it to the appropriate services.

The AWS ALB is ideal for advanced load balancing of HTTP and HTTPS traffic, providing improved performance and reliability for your applications. It operates at the request level, routing traffic to targets within Amazon VPC based on the content of the request. It can handle the varying load of your application traffic in a single Availability Zone or across multiple Availability Zones.

Below is a Pulumi program that sets up:

1. An AWS VPC for your application to reside in.
2. Subnets for the ALB to operate within.
3. An ALB to distribute incoming application traffic.
4. Target groups for the ALB to route requests to different tiers of the application.
5. Listeners for the ALB to listen for incoming traffic on different protocols and ports.

Throughout this program, I will explain each section, detailing what each resource does and how they all tie together to form your multi-tier application load balancer.

```python
import pulumi
import pulumi_aws as aws

# Create a new VPC for our application with cidr_block
vpc = aws.ec2.Vpc("app-vpc",
    cidr_block="10.0.0.0/16")

# Create subnets for the Application Load Balancer
# Public subnets are for the ALB which must be accessible from the internet
public_subnet1 = aws.ec2.Subnet("app-subnet-1",
    vpc_id=vpc.id,
    cidr_block="10.0.1.0/24",
    availability_zone="us-west-2a")

public_subnet2 = aws.ec2.Subnet("app-subnet-2",
    vpc_id=vpc.id,
    cidr_block="10.0.2.0/24",
    availability_zone="us-west-2b")

# Create an Internet Gateway for the VPC so that the ALB can communicate with the internet
igw = aws.ec2.InternetGateway("app-igw",
    vpc_id=vpc.id)

# Create a Route Table, which is used to route network traffic from the subnets to the internet using the Internet Gateway
route_table = aws.ec2.RouteTable("app-rt",
    vpc_id=vpc.id,
    routes=[
        aws.ec2.RouteTableRouteArgs(
            cidr_block="0.0.0.0/0",
            gateway_id=igw.id,
        ),
    ])

# Associate our Route Table with our public subnets
route_table_assoc1 = aws.ec2.RouteTableAssociation("app-rta-1",
    subnet_id=public_subnet1.id,
    route_table_id=route_table.id)

route_table_assoc2 = aws.ec2.RouteTableAssociation("app-rta-2",
    subnet_id=public_subnet2.id,
    route_table_id=route_table.id)

# Create an Application Load Balancer (ALB) to distribute incoming application traffic
alb = aws.alb.LoadBalancer("app-alb",
    internal=False,
    load_balancer_type="application",
    security_groups=[], # Here you would specify the ID of security group(s) for your ALB if needed
    subnets=[public_subnet1.id, public_subnet2.id])

# Create target groups for the ALB to route requests to
tg_primary = aws.alb.TargetGroup("app-tg-primary",
    port=80,
    protocol="HTTP",
    vpc_id=vpc.id,
    health_check=aws.alb.TargetGroupHealthCheckArgs(
        healthy_threshold=3,
        unhealthy_threshold=3,
        timeout=3,
        path="/health",
        interval=30,
    ))

tg_secondary = aws.alb.TargetGroup("app-tg-secondary",
    port=8080,
    protocol="HTTP",
    vpc_id=vpc.id)

# Create listeners for the ALB to listen for incoming traffic on HTTP port 80
listener = aws.alb.Listener("app-listener",
    load_balancer_arn=alb.arn,
    port=80,
    default_actions=[aws.alb.ListenerDefaultActionArgs(
        type="forward",
        target_group_arn=tg_primary.arn)])

# Expose the DNS name of the ALB to access it from the internet
pulumi.export('alb_dns', alb.dns_name)
```

This program does the following:

- It creates an AWS VPC (`Vpc`) and subnets (`Subnet`) for your application to live in a separated and secured network space.
- It sets up an Internet Gateway (`InternetGateway`) and Route Table (`RouteTable`) to allow your ALB to communicate with the internet.
- It deploys an Application Load Balancer (`LoadBalancer`) that listens on HTTP port 80.
- It creates target groups (`TargetGroup`) for the ALB, where you will eventually register your application instances.
- It establishes a listener (`Listener`) that listens on port 80 and routes traffic to your target group.

The health check on the target group monitors the health of your application servers, ensuring that traffic is only sent to healthy instances.

For real-world usage, be sure to:

- Assign a security group to your ALB that allows incoming traffic on the ports you are using.
- Register instances or other targets such as ECS services or Lambda functions with your target groups so that the ALB can route traffic to them.
- Customize health check paths and other parameters according to your application’s requirements.

After running this Pulumi program with the Pulumi CLI, the infrastructure for your AI application’s load balancing will be set up. You can access the application via the DNS name of the ALB, which is exported at the end of the program.