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.