Building Docker Images on Travis CI

Apr 6, 2016

⚠️ This post is archived.

Docker has been the star of the recent times and I have recently been building a lot of Docker images, deploying them to both development and production (luckily yes!).

Travis CI is one of the most popular CI services and I have lately been using it extensively. It is awesome!

Travis CI YAML

Here is a simple .travis.yml to get started with Docker builds on Travis.

sudo: required

services:
  - docker

env:
  # IMPORTANT! Add your docker slug here (commit once)
  - DOCKER_REPO_SLUG=activatedgeek/mariadb

script:
  # build latest image always
  - docker build -t $DOCKER_REPO_SLUG:latest .
  # build the tagged image
  - if [[ $TRAVIS_TAG = $TRAVIS_BRANCH ]]; then docker build -t $DOCKER_REPO_SLUG:$TRAVIS_BRANCH .; else true ; fi

after_success:
  # IMPORTANT! Add the environment variables in Travis Build Environment (one time!)
  - docker login -e="$DOCKER_EMAIL" -u="$DOCKER_USERNAME" -p="$DOCKER_PASSWORD"
  # push to latest if master branch
  - if [[ $TRAVIS_BRANCH = master ]]; then docker push $DOCKER_REPO_SLUG:latest; else true; fi
  # push tag as well
  - if [[ $TRAVIS_TAG = $TRAVIS_BRANCH ]]; then docker push $DOCKER_REPO_SLUG:$TRAVIS_TAG; else true ; fi

Here is how the build behaves under different scenarios:

Push to a branch other than master -> Builds image and exits
Push to branch master -> Builds the image tag latest
Push a tag -> Builds the image with corresponding git tag

Notes

As a reference project, have a look at https://github.com/activatedgeek/docker-mariadb.

The corresponding Travis builds are available publicly at https://travis-ci.org/activatedgeek/docker-mariadb.

Assumptions

The Docker build always uses the default Dockerfile present in the root of the project
The Docker image is always pushed to Docker Hub.

The implications of above two assumptions are easy to overcome if need be.