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Cloudflare Worker: DNS Switching

Cloudflare Worker: DNS Switching


In today's digital landscape, maintaining high availability and uptime for web applications is crucial. Cloudflare Workers, a serverless compute platform, offers a powerful solution for optimizing site performance and reliability. In this blog post, we'll explore a script leveraging Cloudflare Workers to implement dynamic DNS switching, a technique that enhances load balancing and contributes to improved site uptime.

Why DNS Switching?

Traditional load balancing involves distributing traffic among multiple servers to ensure optimal resource utilization. However, these approaches often require complex setups and can be challenging to manage. DNS switching using Cloudflare Workers presents a simpler yet effective alternative.

This script continuously monitors the availability of primary and backup servers and dynamically switches the DNS record to direct traffic to the most responsive server. By automating this process, you can achieve load balancing, distribute traffic efficiently, and enhance the overall reliability and availability of your site.

The Cloudflare Worker Script

Here's the Cloudflare Worker script that implements dynamic DNS switching:

Step-by-Step Guide


  1. Cloudflare Account: Ensure you have a Cloudflare account. If not, sign up at Cloudflare.

Getting Cloudflare API Credentials and Zone ID

  1. Login to Cloudflare Dashboard:
  2. Retrieve API Key:
    • Navigate to "My Profile" > "API Tokens."
    • Create a new API Token with the required permissions (Zone, DNS, etc.). Copy the API Key.
  3. Find Account ID:
    • Go to "My Profile" > "API Tokens."
    • The Account ID is displayed on the right side under "API Tokens."
  4. Get Zone ID:
    • Select the domain you want to configure.
    • The Zone ID is displayed in the Overview section.

Deploying the Cloudflare Worker Script

  1. Create a Worker:
    • Go to the Cloudflare Dashboard.
    • Select your domain.
    • Navigate to the "Workers" tab.
    • Click "Create a Worker."
  2. Paste the Script:
    • Replace the existing script with the dynamic DNS switching script provided above.
  3. Set Variables:
    • Replace the placeholder values for CF_API_EMAIL, CF_API_KEY, CF_ACCOUNT_ID, ZONE_ID, PRIMARY_IP, and BACKUP_IP with your Cloudflare API credentials, account ID, and specific IP addresses.
  4. Save and Deploy:
    • Click "Save and Deploy" to activate the Cloudflare Worker.
  5. Configure Cron Triggers
    1. In the worker detail page, find the "Triggers" section.
    2. Look for the option to "Add Trigger" or a similar button.
    3. Choose "Cron" as the trigger type.
    4. Enter the desired cron expression for the schedule when you want the worker to execute. For example, you might use "*/1 * * * *" to run the worker every minute.
  6. Click "Add Trigger" or a similar button to save the cron trigger.

Observing the Benefits

With the DNS switching script in place, Cloudflare Workers will automatically handle load balancing by directing traffic to the most available server. This improves the overall uptime and performance of your site, ensuring a seamless experience for your users.


DNS switching using Cloudflare Workers provides a simplified approach to load balancing, offering improved site availability and responsiveness. By following this step-by-step guide, you can easily deploy the script and leverage Cloudflare's infrastructure to enhance the reliability of your web applications.