Using aws route53 with ecs

Question

Pulumi · Accepted Answer

In order to use AWS Route 53 with Amazon ECS (Elastic Container Service), you would typically set up an ECS service and then create a DNS record that points to the load balancer in front of your ECS service. Amazon ECS can be used with AWS Fargate for serverless container execution, or with EC2 instances to have more control over the environment.

Here's how you'd set this up in Pulumi using TypeScript:

1. Create an ECS cluster.
2. Define a task definition that specifies how containers should be run.
3. Create a Fargate service that references the task definition and runs the containers.
4. Create a load balancer to distribute traffic to the containers in the service.
5. Register the load balancer with Route 53 to route traffic to your domain.

Below is a detailed program that accomplishes this. This example is simplified and assumes you already have a hosted zone created in Route 53.

```typescript
// Import necessary libraries and Pulumi packages for AWS resources
import * as pulumi from "@pulumi/pulumi";
import * as aws from "@pulumi/aws";
import * as awsx from "@pulumi/awsx";

// Create an ECS cluster to manage services
const cluster = new aws.ecs.Cluster("app-cluster", {
    // Additional AWS resource tags here
    tags: {
        // Tags can help organize and locate your resources and are often a best practice.
        "Name": "app-cluster",
    },
});

// Define the ECS task definition with a single container from the NGINX image
const appTask = new aws.ecs.TaskDefinition("app-task", {
    // Assign CPUs and Memory for the container
    // "FARGATE" requires that these be specified at the task level.
    cpu: "256",
    memory: "512",
    // The networking mode to use for the containers in the task. Required for Fargate.
    networkMode: "awsvpc",
    // Specify this task to run on Fargate
    requiresCompatibilities: ["FARGATE"],
    // Execution role that the Amazon ECS container agent and the Docker daemon can assume.
    executionRoleArn: ecsExecutionRole.arn,
    // Define the container to run; this example uses just one container
    containerDefinitions: pulumi.all([appImage, appPort]).apply(([image, port]) => JSON.stringify([{
        name: "my-app",
        image,
        memory: 256,
        essential: true,
        portMappings: [{
            containerPort: port,
            hostPort: port,
            protocol: "tcp",
        }],
    }])),
});

// Set up a load balancer to distribute traffic to the ECS service
const appLoadBalancer = new awsx.elasticloadbalancingv2.ApplicationLoadBalancer("app-lb", {
    // Use all the subnets associated with this VPC for the load balancer
    subnets: pulumi.output(vpc.publicSubnetIds),
});

// Set up a listener for the load balancer that directs traffic to your service
const webListener = appLoadBalancer.createListener("web-listener", {
    // Listen to HTTP traffic on port 80
    port: 80,
    // Actions specify the routing and handling for incoming requests
    defaultActions: [{
        type: "forward",
        targetGroupArn: webListenerDefaultTargetGroup.arn,
    }],
});

// Create the service with the load balancer
const appService = new awsx.ecs.FargateService("app-svc", {
    cluster: cluster.arn,
    taskDefinition: appTask.arn,
    desiredCount: 2, // This example runs two instances of the container.
    loadBalancers: [{
        // Connect the service to the load balancer established above
        targetGroupArn: webListenerDefaultTargetGroup.arn,
        containerName: "my-app",
        containerPort: 80,
    }],
});

// Obtain the DNS name of the load balancer to use in the DNS record
const appLoadBalancerDnsName = webListener.endpoint.hostname;

// Create a DNS record for the app using AWS Route 53
const appDnsRecord = new aws.route53.Record("app-dns-record", {
    // Zone ID for the domain you are managing
    zoneId: pulumi.output(hostedZone.id),
    // Subdomain or domain to manage
    name: "app",
    type: "A",
    // Use an ALIAS record for integration with the AWS load balancer
    aliases: [{
        name: appLoadBalancerDnsName,
        zoneId: appLoadBalancer.zoneId,
        evaluateTargetHealth: true,
    }],
});

// Output the DNS name where the app is served
export const appUrl = pulumi.concat("http://", appDnsRecord.name);
```

### Explanation

- **ECS Cluster**: We start by creating an ECS Cluster, which is a grouping of ECS services.
- **Task Definition**: Defines the details of the container we want to run, such as the image, resources, and ports. In this example, it uses NGINX as the container image.
- **Load Balancer**: We then create an AWS Load Balancer to distribute incoming HTTP traffic across multiple instances of our task running.
- **Fargate Service**: The ECS Fargate Service runs our task definition with the specified number of desired instances and connects the service to the load balancer.
- **Route 53 Record**: This creates a DNS A record that points to the load balancer where our application is exposed. It uses an ALIAS record, which is a Route 53 feature allowing seamless integration with AWS resources like load balancers.
- **Exports**: The program exports the URL for the application, which can be accessed to interact with the deployed service.

The use of ECS Fargate allows you to run containers without having to manage servers or clusters of Amazon EC2 instances, which is a convenient and scalable option for containerized applications. The load balancer provides a consistent entry point for users to access the service, and Route 53 manages the domain-related configurations.

Remember to replace placeholders like `appImage`, `appPort`, `vpc`, `hostedZone`, and `ecsExecutionRole` with actual references or values you have. This code won't create a new VPC or Route 53 hosted zone; it assumes these already exist and you refer to them by either importing them or referencing existing resources in your Pulumi stack.