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Deploying with Gitlab CI

Gitlab-CI can be used to automatically deploy a Dokku application using the ilyasemenov/gitlab-ci-git-push image docker image.

Prerequisites

Make sure you have a Gitlab account and a Dokku project hosted on Gitlab. This method works whether if you are using buildpacks or Dockerfile.

Make sure you have set up an app on the remote machine following these instructions and can successfully deploy to it from the local machine.

Deploy automatically to production

Add a secret variable

Browse to the repository in question and visit the following path: the Gitlab project > Settings > CI/CD.

Click on Secret variables > Expand and fill in the blanks.

  • Key: SSH_PRIVATE_KEY

  • Value: paste in an SSH private key registered in Dokku:

    -----BEGIN RSA PRIVATE KEY----- ... -----END RSA PRIVATE KEY-----

  • Environment scope: production (This make sure that SSH_PRIVATE_KEY is not available on merge requests or tests)

  • Protected: Do not check this checkbox unless you know what you are doing

Add CI script

Create a file named .gitlab-ci.yml at the root directory of the repository with the following contents:

stages:
  - deploy

variables:
  APP_NAME: node-js-app

deploy:
  image: ilyasemenov/gitlab-ci-git-push
  stage: deploy
  environment:
    name: production
    url: https://$APP_NAME.dokku.me/
  only:
    - master
  script:
    - git-push ssh://dokku@dokku.me:22/$APP_NAME

You will need to modify the APP_NAME variable to the correct value for your application name.

Running git push origin master will now trigger a gitlab-ci pipeline that will automatically deploy your application to your Dokku server. Go to your project on Gitlab and visit "Project > Pipelines" to see the deployment log.

Review Applications

One useful feature of gitlab is to be able to create review applications for non-production branches. This allows teams to review changes before they are pushed to production. First, recreate the SSH_PRIVATE_KEY secret - do not delete the existing secret - but scoped to the review/* environment. This will allow non-production gitlab environments access to the secret.

Next, we'll need to create the review_app gitlab job in our .gitlab-ci.yaml.

review_app:
  image: ilyasemenov/gitlab-ci-git-push
  stage: deploy
  environment:
    name: review/$CI_ENVIRONMENT_SLUG
    url: https://$CI_ENVIRONMENT_SLUG.dokku.me/
    on_stop: stop_review_app
  only:
    - branches
  except:
    - master
  script:
    - mkdir -p ~/.ssh && echo "$SSH_PRIVATE_KEY" | tr -d '\r' > ~/.ssh/id_rsa && chmod 600 ~/.ssh/id_rsa
    - ssh-keyscan -H 22 "dokku.me" >> ~/.ssh/known_hosts
    - ssh -t dokku@dokku.me -- apps:clone --ignore-existing --skip-deploy "$APP_NAME" "$CI_ENVIRONMENT_SLUG"
    - git-push ssh://dokku@dokku.me:22/$CI_ENVIRONMENT_SLUG

The first two lines ensure that Gitlab can talk to the Dokku server. Next, we take advantage of the apps:clone command, and clone the existing application and all of it's configuration to a new location. If the new application already exists, the third line of the script step will be ignored. We also ignore the first deploy script to speed up the cloning process. Finally, the fourth line of the script step will deploy the code as normal.

The above only runs for non-master branches, and will also trigger an on_stop job called stop_review_app. When the branch is deleted or the code is merged, the stop_review_app job will be triggered.

stop_review_app:
  image: ilyasemenov/gitlab-ci-git-push
  stage: deploy
  environment:
    name: review/$CI_ENVIRONMENT_SLUG
    action: stop
  when: manual
  script:
    - mkdir -p ~/.ssh && echo "$SSH_PRIVATE_KEY" | tr -d '\r' > ~/.ssh/id_rsa && chmod 600 ~/.ssh/id_rsa
    - ssh-keyscan -H 22 "dokku.me" >> ~/.ssh/known_hosts
    - ssh -t dokku@dokku.me -- --force apps:destroy "$CI_ENVIRONMENT_SLUG"

The stop_review_app step will delete the temporary application, cleaning up now unused server resources.

Going further, the following modifications can be done:

  • Notify via chat whenever a review application is created/destroyed.
  • Push to a separate, staging server as opposed to a production server.
  • Clone a "staging" application so that review applications do not affect production datasets.
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