Automated Website Deployment With Docker

Fully automated deployment is often the holy grail for users of static site generators like Hugo or Jekyll, providing the convenience of easily pushing new content without sacrificing the lightweight results. Today I’m going to share my process for doing this with my website using Docker and the ecosystem that’s grown up around it.

Creating a Docker Image

First, I started by Dockerizing my website. With a fully static tree, the Dockerfile is cake mix. Most popular web servers have official images on Docker Hub, lately I’ve been using Caddy. For the first version of my Dockerfile, I started with Caddy’s image, then simply inject both my configuration file and the public directory.

FROM caddy:2-alpine

COPY Caddyfile /etc/caddy/Caddyfile
COPY public /var/www/html

This was nice, but I use Hugo, which means that the site needs to be built before the public directory gets pulled into the image. To integrate this into the image building process, I added on an intermediate image to my Dockerfile to run Hugo. There are plenty of community images that contain Hugo, but I found it easier to simply start with an Alpine Edge container and install Hugo from there. After running hugo build in the first stage, the results are copied into the final image. Here’s the final Dockerfile:

FROM alpine:edge

RUN apk add hugo
RUN hugo version

COPY . /src
RUN hugo --minify
RUN ls /src/public

FROM caddy:2-alpine

COPY Caddyfile /etc/caddy/Caddyfile
COPY --from=0 /src/public /var/www/html

Automatically Pulling New Images in Production

Armed with a fully self-contained image of my website, I docker-compose’d to glory on my production server with web ports forwarded to the container and some of Caddy’s directories mounted as volumes to avoid losing SSL certificates.

At this point I would still need to manually log in to my server to pull new images. Enter Watchtower. On a system where all containers should be updated automatically, Watchtower doesn’t require any fancy configuration. I also run some third-party containers that I would rather pull manually however, so this wouldn’t quite work.

Thankfully, Watchtower can be configured for this pretty easily. Out of the box it only ignores specific containers if instructed, an added environment variable does the oppposite, which worked better for my case. From there I added my website container as an exception. Here’s a snippet of my docker-compose.yml:

  image: containrr/watchtower
    - /var/run/docker.sock:/var/run/docker.sock

    com.centurylinklabs.watchtower.enable: "true"

Tying Everything Together

The last piece of the puzzle remaining was to get my image to build and upload to a registry automatically on push. Most any CI solution would have done the trick here, but I settled on using Docker Hub itself to settle both items. The completed chain is this:

  • I make changes to the Git repository and push to master on GitHub

  • Docker Hub picks up on this and queues an image build

  • Watchtower finds the new image and pulls it onto my production server

With this setup, all I need to to be able to update my website is a text editor and Git. There’s certainly room for refinement, but that will be a topic for a later post…