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Using Travis CI to publish to GitHub pages with custom domain

As of yesterday, this blog is automatically being published via Travis CI. When I push a new commit to my GitHub repository it triggers a new build in Travis CI. The build completes and the the git repository is then updated with the generated output (mostly HTML with some static CSS).

The overall flow looks as follows:

High level flow

This is how I set it all up.

Please see issue issue.

Blog repository setup

I use pelican as my blog engine. The "source" code for my blog lives at the amitsaha.github.io repository's site branch. Besides the content (markdown and restructured text files) and pelican specific files, the important files related to publishing are:

  • Dockerfile
  • Makefile
  • .travis.yml

The Dockerfile is used in Travis for building the site and is as follows:

FROM ubuntu:latest

RUN apt-get update && apt-get -y install python3-pip make bash git
RUN pip3 install pelican pelican-youtube markdown pelican-gist
RUN git clone https://github.com/gfidente/pelican-svbhack /tmp/pelican-svbhack
RUN git clone --recursive https://github.com/getpelican/pelican-plugins /tmp/pelican-plugins
WORKDIR /site
ENTRYPOINT ["make", "build"]

The Makefile has a number of targets, but only the build target is currently being used:

build:
    $(PELICAN) $(INPUTDIR) -o $(OUTPUTDIR) -s $(PUBLISHCONF) $(PELICANOPTS)
    cp 404.md $(OUTPUTDIR)/

The first command generates the site and places the generated files in the output sub-directory. In addition we also copy the 404.md file to the output directory to serve a custom 404 page.

The contents of the output sub-directory is what we copy to the master branch. This is done via Travis CI via the instructions in the .travis.yml file.

To summarize, my blog has two branches:

  • site: "source" for the blog and other files necessary for generating the HTML for the blog
  • master: The generated HTML files live in this branch

The generation step is done via Travis and the generated files are pushed to the master branch.

Generating the blog

The .travis.yml file is read by Travis CI and is the entry point for what happens when we push a commit to the site branch of the repository. Below I reproduce snippets from the file and their function.

The blog source is in the site branch so we want to only build when a push has been made to that branch:

branches:
  only:
  - site
git:
  depth: false

We also don't bother cloning more than the last commit (Learn more).

Next, we configure the language and specify that we want to use docker:

language: generic

The generic language ensures that our .travis.yml completely controls what commands are run as part of our build.

We use docker to carry out the build and generation. To do so, we have to specify the following:

sudo: required
services:
  - docker

(To learn more about docker in Travis CI, see this)

We then specify the before_install and install steps. The before_install step builds the docker image:

before_install:
  - docker build -t amitsaha/pelican  .

The install step then creates a container from the image we just built:

install:
  - docker run -v `pwd`:/site -t amitsaha/pelican

The install step runs a container which populates the output sub-directory with the generated files.

The remaining step is to tell Travis CI's GitHub pages "deployer" to deploy the generated output files:

deploy:
  provider: pages
  skip_cleanup: true
  github_token: $GITHUB_TOKEN # Set in travis-ci.org dashboard
  on:
    branch: site
  target_branch: master
  local_dir: ${TRAVIS_BUILD_DIR}/output
  fqdn: echorand.me 

We we will learn how we set the environment variable, GITHUB_TOKEN in a later section.

We basically tell travis CI that we want the build to be done on the site branch and the generated files from the local_dir directory to be pushed to the target_branch which is master.

Setting the fqdn to the custom domain updates the repository settings in GitHub and also adds a CNAME file in the master branch (Learn more). Please see documentation on how to setup a custom domain from scratch.

Travis CI repository settings

Adding the repository to Travis CI

We will then login to Travis CI and follow the guide to add our repository. Under the hood, this step adds a new service integration to our repository. We can see the integrations at https://github.com/<username>/<repository>/settings/installations

If you are logging in for the first time using GitHub (or signing up), you will be presented with the following:

Travis CI permissions

Travis CI repository settings

Next, we will configure the repository settings in Travis to add the GITHUB_TOKEN environment variable and set the value to a generated a personal access token. You can generate one by going to https://github.com/settings/tokens and giving it only the repo OAuth scope.

Travis CI repository settings

Links

Hope you find the post useful. I reverse engineered this process after having already done all the setup, so I may have missed something. Please let me know (link below).

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© Amit Saha. Built using Pelican. Theme by Giulio Fidente on github.