Managing Multiple SaaS on a Single Server with Caddy

1. Probleme

The problem: I have a single VPS in the cloud, and I have many apps that I code myself or services (Bitwarden, Nextcloud…) that I want to expose to the public. So sometimes I may want to have more than one domain for a single machine. Is that possible?

The answer is yes.

This may seem trivial to a lot of people, but back in December 2022, I wasn’t sure if this was possible and how to do it. I had used cloud services like Vercel and Netlify a lot in the past, but I wanted to understand how things really work behind the scenes when you manage the infrastructure yourself.

There are well-known tools to handle these issues, like Apache and Nginx. But I adopted a newcomer that is ultra-simple in terms of configuration.

2. Discovering Caddy

The prerequisite is, of course, to have one or more domain names pointing to your VPS. Then, you need to install Caddy. There are two approaches: you can either use your Linux distribution’s package manager, or you can install Caddy using Docker Compose.

The latter is a faster method to get a working Caddy, but it will also require you to create a common network for all your containers. By default, containers do not see each other and cannot communicate. For native installation, gothere,

$ sudo apt install -y debian-keyring debian-archive-keyring apt-transport-https curl
$ curl -1sLf 'https://dl.cloudsmith.io/public/caddy/testing/gpg.key' | sudo gpg --dearmor -o /usr/share/keyrings/caddy-testing-archive-keyring.gpg
$ curl -1sLf 'https://dl.cloudsmith.io/public/caddy/testing/debian.deb.txt' | sudo tee /etc/apt/sources.list.d/caddy-testing.list
$ sudo apt update
$ sudo apt install caddy

Once the installation is done, you will need to modify the Caddyfile. The structure of this file resembles JSON.

$ vim /etc/caddy/Caddyfile

Your file should look like this:

saas1.com {
	reverse_proxy http://localhost:3000   // one saas
}

saas2.com {
	reverse_proxy  http://localhost:4000  // another saas
}

blog.saas1.com {
	reverse_proxy  http://localhost:8080   // you can liiteraly have infinte amount of service with sub-domain
}

To start the Caddy daemon:

$ sudo systemtcl start caddy
$ sudo systemtcl enable caddy

Don’t forget to restart the Caddy service after each modification to the Caddyfile with the restart command.

By default, Caddy also handles SSL, which is very convenient. So, all the entries we’ve created here will be accessible via https.

Of course, you can do more complex things with Caddy, but here I just wanted to illustrate the simplicity of Caddy and how you can quickly set up a reverse proxy on your VPS. Now you’re done, you can start coding your own SaaS and expose them on your server !