Using aws sfn with applicationloadbalancing

Question

Pulumi · Accepted Answer

To integrate AWS Step Functions (SFN) with Application Load Balancing (ALB), you would typically set up an AWS SFN State Machine to define your application's workflow. Then, you would configure an ALB with a listener that routes traffic to a target group, which, depending on your use case, might trigger executions of your Step Functions state machine.

Here's a conceptual overview of what you'll do in this Pulumi program:
1. Create a Step Functions State Machine that will define the states and transitions for your application logic.
2. Set up an Application Load Balancer with a listener and a default target group.
3. Configure an AWS Lambda function, which could be invoked by the ALB to start execution of your Step Functions state machine.
4. Define integration between the ALB listener and the Lambda function, so HTTP requests to the ALB can trigger the state machine via the Lambda function.

Below is a Pulumi program that demonstrates how to set up the infrastructure mentioned above. The specifics of your Lambda function and state machine definition would be tailored to your particular application logic.

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

// Define the Step Functions State Machine
const stateMachineRole = new aws.iam.Role("stateMachineRole", {
    assumeRolePolicy: aws.iam.assumeRolePolicyForPrincipal({ Service: "states.amazonaws.com" }),
});

const helloWorldStateMachine = new aws.sfn.StateMachine("helloWorldStateMachine", {
    roleArn: stateMachineRole.arn,
    definition: `{
        "Comment": "A simple minimal example of the States language",
        "StartAt": "HelloWorld",
        "States": {
            "HelloWorld": {
                "Type": "Pass",
                "Result": "Hello World!",
                "End": true
            }
        }
    }`,
});

// Create an Application Load Balancer targeting an HTTP endpoint
const alb = new awsx.lb.ApplicationLoadBalancer("net-lb", {
    external: true, // Set to false if you want internal
    idleTimeout: 400,
    enableHttp2: true,
});

const listener = alb.createListener("listener", { port: 80, external: true });

// Define a Lambda Function which will start the Step Functions state machine execution
const lambdaRole = new aws.iam.Role("lambdaRole", {
    assumeRolePolicy: aws.iam.assumeRolePolicyForPrincipal({ Service: "lambda.amazonaws.com" }),
});

const lambda = new aws.lambda.CallbackFunction("startStateMachine", {
    role: lambdaRole,
    callback: async (event) => {
        // Set up AWS SDK and start the state machine execution
        // Parse event, etc. and invoke the Step Functions state machine
    },
});

// Grant necessary permissions for the Lambda function to start State Machine executions
const lambdaPolicyAttachment = new aws.iam.RolePolicyAttachment("lambdaPolicyAttachment", {
    role: lambdaRole,
    policyArn: aws.iam.ManagedPolicy.AWSLambdaBasicExecutionRole,
});

const lambdaSfnPolicy = new aws.iam.RolePolicy("lambdaSfnPolicy", {
    role: lambdaRole,
    policy: {
        Version: "2012-10-17",
        Statement: [{
            Effect: "Allow",
            Action: "states:StartExecution",
            Resource: helloWorldStateMachine.arn,
        }],
    },
});

// Integrate the Lambda function with the ALB listener
listener.addListenerRule("lambdaRule", {
    actions: [{
        type: "forward",
        targetGroupArn: lambda.targetGroup.arn,
    }],
    conditions: [{
        pathPattern: {
            values: ["/start"],
        },
    }],
});

// Export the URLs to access the ALB
export const albUrl = alb.endpoint.hostname;
export const listenerArn = listener.listener.urn;

```

This program does the following:
- Defines a state machine with a single "HelloWorld" state that passes through a message (replace this definition with your actual state machine logic).
- Sets up an external Application Load Balancer (ALB) with a listener on port 80.
- Creates an AWS Lambda function designed to be invoked by the ALB; this function will start execution of your state machine (implement the actual logic for starting the execution inside the callback).
- Connects the Lambda function with the listener's rule, triggering the lambda when a request with the path `/start` is received.

Before running this code, make sure you have the AWS Pulumi provider configured with appropriate credentials and default region.

Keep in mind that this is a high-level example and you need to replace dummy code (like the Lambda callback content) with your actual application logic. This code should be run inside your Pulumi project, and you'll need to have the AWS CLI configured with the right permissions to create these resources.

Make sure to protect sensitive information (such as IAM role policies) and modify resource configurations (like the ALB's parameters and the state machine definition) according to your security and functional requirements.