Balancing traffic with round-robin DNS using CNAME records.

Round-robin DNS is a technique that enables the distribution of network traffic across multiple servers using DNS records. It is one of the simplest methods of load balancing and can be achieved by creating multiple DNS records with the same name but different values that point to various servers.

Below is a Pulumi program written in TypeScript that demonstrates how to set up round-robin DNS using AWS Route 53. Route 53 is Amazon's DNS service that allows you to manage your DNS records. In this example, we will create a hosted zone for a domain and then add multiple CNAME records pointing to different server addresses. Each CNAME record will share the same name (e.g., www) but will resolve to different IP addresses.

Let's walk through the code:

We import the necessary Pulumi and AWS packages.
We create a new hosted zone for our domain.
We add multiple CNAME records within the hosted zone. These records will have a TTL (time to live) value that indicates how long DNS resolvers should cache the response. A TTL of 300 seconds (5 minutes) is common for dynamic DNS configurations like round-robin.
We set the roundRobinRecords variable, which is an array of different IP addresses (in this case, subdomains) where our traffic will be distributed.
We loop through the roundRobinRecords and create a CNAME record for each IP address, making sure they all have the same record name but different values.

Here's the complete program:

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

// Replace with your domain name
const domainName = "example.com";

// Create a new Route 53 zone for the domain
const zone = new aws.route53.Zone("my-zone", {
    name: domainName,
});

// Define round-robin CNAME records
const roundRobinRecords = [
    "server1.example.com",
    "server2.example.com",
    "server3.example.com",
];

// Create CNAME records to balance traffic across servers
roundRobinRecords.forEach((serverAddress, index) => {
    new aws.route53.Record(`www-record-${index}`, {
        zoneId: zone.id,
        name: "www", // Subdomain part of the URL (e.g., www.example.com)
        type: "CNAME",
        ttl: 300,
        records: [serverAddress],
    });
});

// Export the domain name and name servers
export const domainNameOutput = domainName;
export const nameServers = zone.nameServers;

By running this Pulumi program and applying it, you will setup round-robin DNS load balancing for www.example.com which will equally distribute traffic between server1.example.com, server2.example.com, and server3.example.com.

Remember to replace example.com and server addresses with your actual domain and server addresses.

After deploying this, DNS queries for www.example.com will be resolved to server1.example.com, server2.example.com, and server3.example.com in a round-robin fashion. The TTL value defines how long each DNS resolution result should be cached, and a lower value can be used for more responsive load balancing adjustments.

Please note that for this code to run, you should have the AWS credentials configured in your Pulumi environment as it requires access to AWS Route 53 services to create and manage DNS records.

Below is the equivalent Pulumi program written in Python, which sets up a Route 53 zone for a specified domain name and creates round-robin CNAME records.

import pulumi
import pulumi_aws as aws

# Replace with your domain name
domain_name = "example.com"

# Create a new Route 53 zone for the domain
zone = aws.route53.Zone("my-zone",
                        name=domain_name)

# Define round-robin CNAME records
round_robin_records = [
    "server1.example.com",
    "server2.example.com",
    "server3.example.com",
]

# Create CNAME records to balance traffic across servers
for index, server_address in enumerate(round_robin_records):
    aws.route53.Record(f"www-record-{index}",
                       zone_id=zone.id,
                       name="www",  # Subdomain part of the URL (e.g., www.example.com)
                       type="CNAME",
                       ttl=300,
                       records=[server_address])

# Export the domain name and name servers
pulumi.export('domain_name_output', domain_name)
pulumi.export('name_servers', zone.name_servers)

This program will create a Route 53 hosted zone and CNAME records using round-robin DNS to distribute traffic among the specified servers.

Balancing traffic with round-robin DNS using CNAME records.

Rewrite this program in Python