Last month I created this site with Jekyll 2.0 and took advantage of the free hosting on GitHub Pages. The deployment process is effortless: git push origin master . If you’ve used Heroku this looks familiar, but on GitHub Pages you won’t see any details of the deployment. So what happens if the build fails?

As I walked through the set up I realised that GitHub Pages does more than host my site—it builds it too. Every time I push a new commit to master , GitHub runs Jekyll to build my static site and serves it to the world via their CDN. Nice!

Unlike other hosts you can’t control the production environment on GitHub Pages. Their generosity has some sensible limits. Thankfully GitHub won’t deploy a failed build, but unless you check your site every time you push you won’t know if your changes have been deployed.

Here’s how I avoid failed builds by using the same versions in development and get a notification when a build fails.

Use the same versions

GitHub publishes the dependencies and versions and provides a handy JSON endpoint. In the Jekyll tutorial it shows how to call the endpoint in your Gemfile and specify the version of the github-pages gem:

source "https://rubygems.org" require "json" require "open-uri" versions = JSON . parse ( open ( "https://pages.github.com/versions.json" ). read ) gem "github-pages" , versions [ "github-pages" ]

This means that with every bundle the production version of the gem will be checked and installed. To keep track of updates I commit my Gemfile.lock to record the last version I’ve used in development. The github-pages gem has been updated twice in the month or so since I created this site.

Ok, so I’m keeping up with changes to the github-pages gem. But what about the Ruby version? The endpoint gives several other details about the GitHub Pages production environment, here’s the full response:

# https://pages.github.com/versions.json { "jekyll" => "2.4.0" , "jekyll-coffeescript" => "1.0.1" , "jyll-sass-converter" => "1.2.0" , "kramdown" => "1.3.1" , "maruku" => "0.7.0" , "rdiscount" => "2.1.7" , "redcarpet" => "3.1.2" , "RedCloth" => "4.2.9" , "liquid" => "2.6.1" , "pygments.rb" => "0.6.0" , "jemoji" => "0.4.0" , "jekyll-mentions" => "0.2.1" , "jekyll-redirect-from" => "0.6.2" , "jekyll-sitemap" => "0.6.3" , "github-pages" => "31" , "ruby" => "2.1.1" }

Aha, there’s the Ruby! So I can specify the production Ruby in my Gemfile as well:

ruby versions [ "ruby" ]

The Ruby version isn’t recorded in Gemfile.lock so I track changes manually in .ruby-version , because I use rbenv to manage my Rubies in development. So when the Ruby version changes in production I see a warning when I bundle , for example:

Your Ruby version is 2.1.0, but your Gemfile specified 2.1.1

Now I know that I’m using the same versions of Ruby and github-pages when I run my site locally so there’s less to go wrong when I deploy to production. And if a build fails after a version upgrade I’ll be able to compare the last working versions recorded in Gemfile.lock and .ruby-version and narrow down the cause.

Get notifications from Travis CI

Checking your site after every push is a chore. And to make things worse, I’m guilty of pushing minor changes without testing. I guess we’ve all done it. I have thrown caution to the wind and broken the build several times, but I get an email shortly afterwards reporting my foolishness. Continuous integration is my friend :o)

Setting up Travis CI for a GitHub Pages site is straightforward. Check out the continuous integration tutorial and never miss a failed build again. I highly recommend using html-proofer to check all your links and images are working too. There’s a number of ways to extend the basic set up, but I’ll leave that for another time.

Take a look at the full source code of this site and good luck with your deployments.