Semaphore CI/CD using Docker Hub (instead of Semaphore's built-in Docker registry)

I recently found a beautifully crafted free ebook on CI/CD, from Semaphore. The name of the book is “CI/CD with Docker and Kubernetes”. You can download it for free.

Chapter 4 of the book is about implementing a CI/CD pipeline. But the commands given in the examples uses the built-in Docker registry of Semaphore, but it’s not available in the free plan. Page 66 of the book says this:

Semaphore’s built-in Docker registry is available under the enterprise plan. If you’re using a free, open-source, or startup plan, use an external service like Docker Hub instead. The pipeline will be slower, but the workflow will be the same.

So I looked for a way on how to use Docker Hub to complete the tutorial.

Below is the complete semaphore.yml file containing the relevant commands for connecting to Docker Hub. Compare it with the original semaphore.yml file.

Note that the blocks named Build and Push contains a prologue for logging into Docker Hub.

Also, you need to replace the Docker Hub repository name. Mine is named jflaga/demo in the .yml file below. Replace that with the name of your repository.

You also need to create a secret in Semaphore for $DOCKERHUB_USERNAME and $DOCKERHUB_PASSWORD.

version: v1.0
name: Docker
agent:
  machine:
    type: e1-standard-2
    os_image: ubuntu2004

blocks:
  - name: Build
    task:
      jobs:
        - name: docker build
          commands:
            - checkout
            - 'docker pull jflaga/demo:latest || true'
            - 'docker build --cache-from jflaga/demo:latest -t jflaga/demo:$SEMAPHORE_WORKFLOW_ID .'
            - 'docker push jflaga/demo:$SEMAPHORE_WORKFLOW_ID'
      secrets:
        - name: Docker Hub Secret
      prologue:
        commands:
          - echo $DOCKERHUB_PASSWORD | docker login --username "$DOCKERHUB_USERNAME" --password-stdin
  - name: Tests
    task:
      prologue:
        commands:
          - 'docker pull jflaga/demo:$SEMAPHORE_WORKFLOW_ID'
      jobs:
        - name: Unit test
          commands:
            - 'docker run -it jflaga/demo:$SEMAPHORE_WORKFLOW_ID npm run lint'
        - name: Functional test
          commands:
            - sem-service start postgres
            - 'docker run --net=host -it jflaga/demo:$SEMAPHORE_WORKFLOW_ID npm run ping'
            - 'docker run --net=host -it jflaga/demo:$SEMAPHORE_WORKFLOW_ID npm run migrate'
        - name: Integration test
          commands:
            - sem-service start postgres
            - 'docker run --net=host -it jflaga/demo:$SEMAPHORE_WORKFLOW_ID npm run test'
  - name: Push
    task:
      jobs:
        - name: Push
          commands:
            - 'docker pull jflaga/demo:$SEMAPHORE_WORKFLOW_ID'
            - 'docker tag jflaga/demo:$SEMAPHORE_WORKFLOW_ID jflaga/demo:latest'
            - 'docker push jflaga/demo:latest'
      secrets:
        - name: Docker Hub Secret
      prologue:
        commands:
          - echo $DOCKERHUB_PASSWORD | docker login --username "$DOCKERHUB_USERNAME" --password-stdin

Enjoy!

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