Create a free go-link server “on edge” using Cloudflare Worker KV

2021-06-06T00:00:00+06:00

Among quite a few ways to implement a go-link server (i.e., url-forwarder, short-url server, etc.), I’m going to show you how to use free-tier Cloudflare Worker (& KV) to create an in-house, on-edge, no-webserver go-link server.

For example, the short-link for this article is go.kmonsoor.com/golink-kv

/latest (by which I mean go.yourdomain.co/latest) may point to https://www.yourcompany.com/about/news which is a public page
/hr-help may point to https://www.company-internal.com/long-link/hr/contact.html, which is company’s internal human-resources help portal
/cnypromo may point to https://shop.yourcompany.com/sales/promotions/?marketing-promo=2021-cny which is a temporary sales promotions page targeting the shoppers during the Chinese new year of 2021.

Please note that using the setup and the code below, it’ll be possible to resolve short-links via a single sub-domain, e.g., go.your-domain.co. However, it’s possible (with some modification of the code) to resolve/redirect via any number of domains (your own, of course) towards any other public or private URL, and all sorts of novelties. However, for brevity’s sake, I will discuss the first one, a single sub-domain usecase.

To set up a go-link server or short-URL resolver via a proper KV+Worker combination, we’ll go through these steps:

Pre-requisites
Create the short-link map as a KV
Mapping a KV to a Worker variable
Handling a route with webworker
Create the Worker
Pointing a DNS record to the Worker
Next step
Related

Pre-requisites¶

The DNS resolver for the root domain (in the example below, kmonsoor.com) needs to be Cloudflare. Because the core of the solution, the “worker”, runs on the nearest (from the user) edge of Cloudflare using a standard KV (“key, value”) list.
Write permission to the DNS configuration as you’d need to add a new AAAA DNS record.
Some knowledge of Javascript(ES6), as we are going to write the “worker” in that language.

Create the short-link map as a KV¶

We’ll start the setup by creating the short-link map, the list between the short-link segments that you (or someone in your org) define, and the actual URLs they need to point to.

Find the KV stuff in the Workers section. From the screenshot, please ignore the “Route” section for now.

you’d need to create a Worker KV “Namespace”. Name the namespace as you seem fit. I named it REDIRECTS (in all caps just as a convention, not required).
List the short links & their respective target URLs. From the examples in the intro, the keys latest, hr-help, cnypromo etc. would be in as the “key”, and the target full links as the respective “value”.
Remember NOT to start the short part with ‘/’. It’ll be taken care of in the code.

Once you’ve listed all your desired (short-link, target-link) combinations, now we have a KV on Cloudflare. However, it’s not referencable from your Worker code, not yet. Hence the next step.

Mapping a KV to a Worker variable¶

Now, we will map the previously created KV to a variable that can be referenced from our Worker code. Please note that though I used different names, it can be the same as well. Also, note that multiple Workers can access a single KV, and vice versa is also true; a single Worker can reference multiple KVs.

Handling a route with webworker¶

Create the Worker¶

Now, we will write Worker-code that runs on V8 runtime on the nearest (from the requesting user) “edge” location of Cloudflare, to execute the code and deliver the result(s) to the user. In this case, that would be to redirect user-requested address to the mapped one (by you, in the KV namespace above).

The code editor looks like this:

If you rather prefer to copy-paste, please feel free to do it from the below GitHub Gist.

Once done, it should look like …

Pointing a DNS record to the Worker¶

Finally, we need to point a DNS record that’ll redirect all requests to your re-soutign sub-domain (e.g. go.your-domain.com) to the Cloudflare Worker that we just created.

According to the Cloudflare docs, the DNNS record must be an AAAA record, pointing to the IPv6 address 100::. The “Name” here is the “sub-domain” part of your choice, which is better be short, to rightfully serve our goal here.

Voila ! Now, test some of the short-urls that you’ve mapped via the KV. Enjoy ! Watch out for the target usage though. Here’s the limit.

I think you’ll be fine, unless you’re some celebrity ;)

Next step¶

As the next step, I’m thinking to create a generic Go/Link resolver browser extension. Then, someone can set their own default domain or company domain of choice as short-domain host. In that case, entering just go/hr-help on the browser will take to https://www.company-internal.com/.../hr/contact.html that we have discussed at the beginning (remember the example case of an internal human resources help portal?).

If you want to do this url-direction on your server, but only using webserver, try this: Personal short-link server using only Caddyserver

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I think ... - Cloudflare KV