Create and manage Custom FlexBalancer Answer

1. Create FlexBalancer with Custom Answer
2. Edit FlexBalancer with Custom Answer
3. Delete FlexBalancer

Create FlexBalancer with custom answer

First of all, log in and proceed to FlexBalancers page:

Select name for your Balancer, Custom code button and press Next Step:

Then, fill in your fallback address. You may also change default TTL, or keep it equal to 10. After that, press Create New FlexBalancer button:

Now, you have text editor open, so you can write or post there your custom code.

Supported language: TypeScript.

Editor: Monaco Editor, see Monaco Editor Accessibility Guide for detailed info. Notice, that you also are able to edit FlexBalancer description, Fallback and TTL.

Let's create our first Custom FlexBalancer with the simpliest logic: we will check uptime of jsDelivr CDN and if it is bigger that 98,5 - return answer 'google.com' with TTL 25, if not - return 'perfops.net' with default TTL (that you have set before).

/* 
 * If jsDelivr uptime is bigger than 98,5 - return 'google.com' with TTL 25
 * else return 'perfops.net' with default TTL 
 */
function onRequest(req: IRequest, res: IResponse) {
    if(fetchCdnRumUptime('jsdelivr-cdn') > 98.5) { // if jsDelivr uptime is high
        res.setCNAMERecord('google.com'); // we set answer address to 'google.com' 
        res.setTTL(25); // with TTL = 25

        return; // return answer
    }
    // if jsDelivr uptime is lower than expected
    res.setCNAMERecord('perfops.net'); // we set answer address to 'perfops.net'
    return; // return answer
}

The text editor checks your code syntax for errors, shows error details on mouse hover and won't allow you to publish code with errors:

It also 'knows' all definitions of our Custom Answers API (functions, type values for particular user) and provides helpful hints (use Ctrl+Space) and auto-completion (use Tab):

Now all changes are done and no errors remain, you simply press Test and Publish button and confirm the deployment:

The next page has important information, do not forget to copy/save CNAME record for further placement into domain settings for your domain, then press Done:

Now you can see your newly created FlexBalancer at FlexBalancers page:

Let's check if your Custom Answer works. After some time, when you already have made all nessessary CNAME changes - check CDN RUM Uptime at CDNPerf. You can see that RUM Uptime is higher than 98,5.

So, according to rules that you have defined at Custom Answer, it should return google.com as response address.

And it does! That means your FlexBalancer works perfectly!

You may want to take a look at our Tutorial and at more complicated script samples stored at our repository.

We have also prepared a small tutorial at our Help Center, that shows you five different ways to test your flexbalancer. Hope, it will be helpful!

Edit FlexBalancer with custom answer

To change your custom answer, proceed to FlexBalancers page and press square button with pen at your Balancer:

You can edit your code, FlexBalancer description, Fallback and TTL, turn your FlexBalancer off and even to Delete it:

After editing, press Test and Publish button, then Deploy now.

Do not forget to copy/save FlexBalancer name for placement into CNAME record of domain settings for your domain, then press Done:

Delete FlexBalancer

Proceed to FlexBalancers page and press red square button with trashcan picture on it:

Confirm the deletion. Keep in mind that it may break your service: