1. Managing DNS Failover with Health Checks using GCP DNS Record Sets

    TypeScript

    When setting up DNS Failover with Health Checks using Google Cloud DNS Record Sets, you want to ensure that your DNS queries are directed to healthy endpoints. In Google Cloud, you would typically set up a health check which monitors a given endpoint for availability, and then use DNS record sets to route traffic. If an endpoint fails a health check, the DNS failover mechanism reroutes traffic to a healthy endpoint.

    To accomplish this, we need to do the following steps:

    1. Create a Health Check to monitor the desired service.
    2. Create a DNS Managed Zone where our DNS records will reside.
    3. Create a DNS Record Set pointing to the healthy endpoint, and associate it with the Health Check.

    Below is a Pulumi program written in TypeScript to set up DNS Failover. The program uses 'gcp.dns.ManagedZone' to create a managed DNS zone, 'gcp.compute.HealthCheck' for health checks, and 'gcp.dns.RecordSet' for DNS record sets with failover policies based on health checks.

    Here's the detailed Pulumi program to achieve this:

    import * as pulumi from "@pulumi/pulumi";
import * as gcp from "@pulumi/gcp";

// Set up a GCP health check resource.
const healthCheck = new gcp.compute.HealthCheck("http-health-check", {
    description: "Health check via HTTP",
    // Basic configuration for the health check
    httpHealthCheck: {
        port: 80,
        requestPath: "/healthz"
    },
    checkIntervalSec: 10, // Frequency of health checks
    timeoutSec: 5, // Timeout per attempt
    healthyThreshold: 2, // Number of successful checks to consider healthy
    unhealthyThreshold: 2, // Number of failed checks to consider unhealthy
});

// Create a DNS Managed Zone in which to declare the DNS Record Set
const managedZone = new gcp.dns.ManagedZone("my-managed-zone", {
    description: "Managed zone for example",
    dnsName: "example.com.", // Be sure to include the trailing dot
});

// Define the Record Set with failover based on the health check
const recordSet = new gcp.dns.RecordSet("www-record-set", {
    name: "www.example.com.", // Be sure to include the trailing dot
    type: "A",
    ttl: 300,
    managedZone: managedZone.name,
    rrdatas: ["192.0.2.1"], // IPs for your web servers
    // Associate a routing policy with the health check for failover
    routingPolicy: {
        healthCheck: {
            healthCheckServer: healthCheck.selfLink,
        }
    },
});

// Export the DNS endpoint
export const dnsEndpoint = pulumi.concat("www.", managedZone.dnsName);

    This Pulumi program will first set up the health check to monitor traffic through HTTP at the given requestPath. The health check parameters determine how often the check is performed and what constitutes a healthy or unhealthy endpoint.

    Next, it creates a DNS Managed Zone for the example.com domain. Within this managed zone, we define a DNS Record Set for the subdomain 'www'. The rrdatas field contains the IP address of your healthy web server.

    The DNS Record Set's routingPolicy is associated with the created Health Check using the healthCheckServer property. The selfLink of the GCP Health Check resource is used to provide the association.

    Lastly, the program exports the DNS endpoint, which combines 'www' with the managed zone's DNS name.

    Remember to replace placeholder values such as "example.com." and IP addresses with actual values from your environment.


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