TedPage: Replacing Docker Hub and Github with Gitlab

I’ve been working on making the Inkscape CI performant on Gitlab because if you aren’t paying developers you want to make developing fun. I started with implementing ccache, which got us a 4x build time improvement. The next piece of low hanging fruit seemed to be the installation of dependencies, which rarely change, but were getting installed on each build and test run. The Gitlab CI runners use Docker and so I set out to turn those dependencies into a Docker layer.

The well worn path for doing a Docker layer is to create a branch on Github and then add an automated build on Docker Hub. That leaves you with a Docker Repository that has your Docker layer in it. I did this for the Inkscape dependencies with this fairly simple Dockerfile:

FROM ubuntu:16.04
RUN apt-get update -yqq 
RUN apt-get install -y -qq <long package list>

For Inkscape though we’d really like to not set up another service and accounts and permissions. Which led me to Gitlab’s Container Registry feature. I took the same Git branch and added a fairly generic .gitlab-ci.yml file that looks like this:

variables:
  IMAGE_TAG: ${CI_REGISTRY}/${CI_PROJECT_NAMESPACE}/${CI_PROJECT_NAME}/${CI_COMMIT_REF_SLUG}:latest

build:
  image: docker:latest
  services:
    - docker:dind
  stage: build
  script:
    - docker login -u ${CI_REGISTRY_USER} -p ${CI_REGISTRY_PASSWORD} ${CI_REGISTRY}
    - docker build --pull -t ${IMAGE_TAG} .
    - docker push ${IMAGE_TAG}

That tells the Gitlab CI system to build a Docker layer with the same name as the Git branch and put it in the project’s container registry. For Inkscape you can see the results here:

• Docker config branch
• .gitlab-ci.yml
• Container Registry

We then just need to change our CI configuration for the Inkscape CI builds so that it uses our new image:

image: registry.gitlab.com/inkscape/inkscape-ci-docker/master

Overall the results were saving approximately one to two minutes per build. Not the drastic results I was hoping for, but this is likely to be caused by the builders being more IO constrained than CPU constrained, so uncompressing the layer is roughly the same cost as installing the packages. This still results in a 10% savings in total pipeline time. The bigger unexpected benefit is that it has cleaned up the CI build logs to where the first page starts the actual Inkscape build instead of having to scroll through pages of dependency installation (old vs. new).