Deploy docker container from external registry to Heroku

Question

I got project repository hosted on gitlab. I am using gitlab-ci to build docker container from my project. What I would like to achieve is deploying that container to heroku.

Answer 1

You are starting the app for some reason (using docker run) you might don't need. The dpl tool is intended to be used inside a codebase, rather than for image deployment. As you said

build_image:
  image: docker:latest
  services:
  - docker:dind
  stage: package
  script:
    - docker login -u gitlab-ci-token -p $CI_BUILD_TOKEN registry.gitlab.com
    - docker build -t registry.gitlab.com/maciejsobala/myApp .
    - docker push registry.gitlab.com/maciejsobala/myApp:latest

is working, what means your runner is able to run docker in docker and successfully pushing images. For heroku deployment, you must only push that image to the heroku docker registry, according to the official heroku documentation. In short you do a

deploy_to_heroku:
  stage: deploy
  services:
  - docker:dind
  script:
    - docker login --email=_ --username=_ --password= registry.heroku.com
    - docker tag registry.gitlab.com/maciejsobala/myApp:latest registry.heroku.com/maciejsobala/myApp:latest
    - docker push registry.heroku.com/maciejsobala/myApp:latest

with your heroku auth token, which you can get by heroku auth:token

As said in the documentation, pushing to herokus registry triggers a release process of the app.