Managing DNS failover with Route53 health checks

Question

Pulumi · Accepted Answer

Managing DNS failover with AWS Route 53 is a way to increase the availability and reliability of your application by automatically routing your users to an alternate location if your primary endpoint becomes unavailable.

Here's how you can achieve this using Pulumi and AWS Route 53 resources:

1. **Health Checks**: You create Route 53 health checks which monitor the health of your endpoints.
2. **DNS Records**: You set up DNS records (like A, AAAA, CNAME) with failover policies.
3. **Record Sets**: Within each DNS record, you specify the primary and secondary resources, associating them with the health checks.
4. **Testing**: It's good practice to test the failover configuration in a controlled environment before deploying it to production.

Below is a Pulumi program written in TypeScript that sets up a basic DNS failover using Route 53 health checks:

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

// Configure AWS provider
const provider = new aws.Provider("aws", {
  region: "us-west-2", // Choose your desired AWS region
});

// Create a health check for the primary endpoint
const primaryHealthCheck = new aws.route53.HealthCheck("primaryHealthCheck", {
  // This should be the fully-qualified domain name of your primary endpoint
  fqdn: "primary.example.com", 
  type: "HTTP",
  failureThreshold: 3,
  requestInterval: 30,
  resourcePath: "/",  // This is the URL path Route53 will request to check health
}, { provider: provider });

// Create a health check for the secondary endpoint
const secondaryHealthCheck = new aws.route53.HealthCheck("secondaryHealthCheck", {
  fqdn: "secondary.example.com",
  type: "HTTP",
  failureThreshold: 3,
  requestInterval: 30,
  resourcePath: "/",
}, { provider: provider });

// Create a DNS zone if you don't have one already
const zone = new aws.route53.Zone("myZone", {
  name: "example.com",
}, { provider: provider });

// Create a failover A record that points to the primary IP
const primaryRecordSet = new aws.route53.Record("primaryRecordSet", {
  // Replace with your Domain name and the desired subdomain
  name: "service.example.com", 
  type: "A",
  zoneId: zone.id, // Reference the ID of the hosted zone created above
  failoverRoutingPolicies: [{
    type: "PRIMARY",
  }],
  // Your primary endpoint IP
  records: ["123.123.123.123"], 
  healthCheckId: primaryHealthCheck.id, // References the primary health check
  setIdentifier: "primaryEndpoint",
  ttl: 60,
}, { provider: provider });

// Create a failover A record that points to the secondary IP
const secondaryRecordSet = new aws.route53.Record("secondaryRecordSet", {
  name: "service.example.com",
  type: "A",
  zoneId: zone.id,
  failoverRoutingPolicies: [{
    type: "SECONDARY",
  }],
  records: ["456.456.456.456"], // Your secondary endpoint IP
  healthCheckId: secondaryHealthCheck.id, // References the secondary health check
  setIdentifier: "secondaryEndpoint",
  ttl: 60,
}, { provider: provider });

export const primaryFqdn = primaryRecordSet.fqdn;
export const secondaryFqdn = secondaryRecordSet.fqdn;
```

In this program, you:
- Define health checks for both primary and secondary endpoints. The `failureThreshold` and `requestInterval` parameters determine when Route 53 considers an endpoint unhealthy.
- Create a DNS zone for your domain (if you don't have one already).
- Set up primary and secondary A records using the `failoverRoutingPolicies` to specify which record is the primary and which is the secondary. The `healthCheckId` field associates each record set with the respective health check.
- Route53 will now monitor the health of these endpoints based on the health checks. If the primary fails, it will failover to the secondary based on the failover routing policies.
- Export the fully qualified domain names of the primary and secondary records.

To run this program, you would need to have Pulumi installed, as well as configured your AWS account for programmatic access (usually by setting the appropriate environment variables or by using an AWS profile). After running `pulumi up`, the resources specified in the program will be provisioned in your AWS account.

For more detailed documentation on the used resources:
- For [Health Checks](https://www.pulumi.com/registry/packages/aws/api-docs/route53/healthcheck/)
- For [DNS Records](https://www.pulumi.com/registry/packages/aws/api-docs/route53/record/)

Remember to replace the example values such as domain names and endpoint IPs with your actual data. Always test your setup in a non-production environment first to verify that failover occurs as expected.