Using aws lb with sfn

Question

Pulumi · Accepted Answer

The integration of AWS Load Balancer (LB) with AWS Step Functions (SFN) typically involves setting up an application or network load balancer to manage incoming traffic and distribute it across multiple endpoints, while AWS Step Functions coordinates the components of distributed applications and microservices using visual workflows.

In a common scenario, users might hit an API endpoint which is sitting behind a load balancer. This invokes a Lambda function that starts an execution of a Step Functions state machine, orchestrating multiple services like additional Lambda functions, DynamoDB, S3, etc.

Here's how you could create both an AWS Load Balancer and an AWS Step Functions State Machine using Pulumi in TypeScript. First, we will define the load balancer and then the state machine.

```typescript
import * as aws from "@pulumi/aws";

// Create a new load balancer
const loadBalancer = new aws.lb.LoadBalancer("my-load-balancer", {
    internal: false,
    loadBalancerType: "application",
    securityGroups: [], // Provide your security group ids here
    subnets: [],       // Provide your subnet ids here
    enableHttp2: true,
});

// Define a target group for the load balancer, which could be a Lambda function
const targetGroup = new aws.lb.TargetGroup("my-target-group", {
    port: 80,
    protocol: "HTTP",
    targetType: "lambda",
    vpcId: "vpc-123456", // Provide your VPC id here
});

// Register a Lambda function into the target group
const lambdaTargetGroupAttachment = new aws.lb.TargetGroupAttachment("lambda-target-group-attachment", {
    targetGroupArn: targetGroup.arn,
    targetId: "my-lambda-function-arn", // Provide your Lambda Function ARN here
});

// Define a listener for the load balancer that will check for incoming requests
const listener = new aws.lb.Listener("listener", {
    loadBalancerArn: loadBalancer.arn,
    port: 80,
    defaultActions: [{
        type: "forward",
        targetGroupArn: targetGroup.arn,
    }],
});

// Create a basic Step Functions state machine with a single task that invokes a Lambda function
const role = new aws.iam.Role("my-sfn-role", {
    assumeRolePolicy: JSON.stringify({
        Version: "2012-10-17",
        Statement: [{
            Action: "sts:AssumeRole",
            Effect: "Allow",
            Principal: {
                Service: "states.amazonaws.com",
            },
        }],
    }),
});

const stateMachine = new aws.sfn.StateMachine("my-state-machine", {
    roleArn: role.arn,
    definition: JSON.stringify({
        Comment: "A simple AWS Step Functions state machine that invokes a Lambda function.",
        StartAt: "InvokeLambdaFunction",
        States: {
            InvokeLambdaFunction: {
                Type: "Task",
                Resource: "arn:aws:states:::lambda:invoke", // This ARN changes if you have a specific Lambda ARN to invoke
                Parameters: {
                    FunctionName: "my-lambda-function-name", // Provide your Lambda Function name here
                    Payload: {
                        "input.$": "$",
                    },
                },
                End: true,
            },
        },
    }),
});

// Outputs
export const loadBalancerDnsName = loadBalancer.dnsName;
export const stateMachineArn = stateMachine.id;
```

This Pulumi program first sets up an application load balancer that can route traffic to an AWS service, such as a Lambda function. The `aws.lb.LoadBalancer` resource specifies the type of the load balancer, while the `aws.lb.TargetGroup` resource defines where incoming traffic should be directed. The `aws.lb.Listener` waits for incoming connections and uses the specified rules