Github Syncing

Now that we have created a container for our project, we will use Github Actions to set up automated Docker build and Docker push triggers.

Initialise Repository

Create a repository on Github called rtp_workshop. Initialise it with a README.md file. Note how the default branch is called main.

On your laptop, move to the directory where you have created the Dockerfile, environment.yml file and the container test.img.

Warning

The maximum file size permitted on Github is 20Mb. We will create a .gitignore file to tell github to ignore the container when pushing to Github.

Create the following .gitignore file in the directory:

*.img

Note

Please make sure you have the latest version of git installed.

Create a remote connection (origin) pointing to our Github repository rtp_workshop:

$ git init # automatically checks out as master branch

$ git remote add origin git@github.com:BarryDigby/rtp_workshop.git

$ git pull origin main # pull README.md

$ git add . # stage local files

$ git commit -m "push to master"

$ git push --set-upstream origin master

We have now created a branch master that contains all of our local files, and the original README.md file used to initialise the repository. If you want to run a sanity check, run git branch -a - you will see that we are on the local master branch, and there are two remotes - main and master (on Github).

Now create a dev branch, and make it even with master:

$ git checkout -b dev # create dev branch

$ git pull origin master # make even with master

$ git push --set-upstream origin dev # create dev branch on Github

$ git branch -a

Great! We have both master and dev locally and on Github. Now I want to delete the main branch (this caused a world of pain when Github decided to stop using the term master).

Do this via Github:

In the rtp_workshop repository, click on the branch icon.
Change the default branch to dev.
Delete the branch main.

We must update these changes in our remote. Go to the directory containing the repository:

$ git checkout dev # go to dev if not already there

$ git remote prune origin # update local to reflect changes we made on Gtihub

$ git branch -a # sanity check.

Docker Workflow

Now that we have set up our github branches correctly, let’s add a trigger: every time we push to dev, the Docker container is built and pushed to Dockerhub.

Locally, using VSCode or the command line, create the file .github/workflows/push_dockerhub_dev.yml:

name: RTP Docker push (dev)
# This builds the docker image and pushes it to DockerHub
# Runs on push events to 'dev', including PRs.
on:
  push:
    branches:
      - dev

jobs:
  push_dockerhub:
    name: Push new Docker image to Docker Hub (dev)
    runs-on: ubuntu-latest
    # Only run for your repo
    if: ${{ github.repository == 'BarryDigby/rtp_workshop' }}
    env:
      DOCKERHUB_USERNAME: ${{ secrets.DOCKERHUB_USERNAME }}
      DOCKERHUB_PASS: ${{ secrets.DOCKERHUB_PASS }}
    steps:
      - name: Check out pipeline code
        uses: actions/checkout@v2

      - name: Build new docker image
        run: docker build --no-cache . -t barryd237/test:dev

      - name: Push Docker image to DockerHub (dev)
        run: |
          echo "$DOCKERHUB_PASS" | docker login -u "$DOCKERHUB_USERNAME" --password-stdin
          docker push barryd237/test:dev

Note

Please substitute BarryDigby with your Github username, and barryd237 with your Dockerhub username.

Github Secrets

Those of you with a keen eye will have noticed two environment variables in the push_dockerhub_dev.yml file: DOCKERHUB_USERNAME and DOCKERHUB_PASS, no prizes for guessing what these stand for.

To set up Github secrets, navigate to your GitHub repository and click Settings > Secrets > New secret. Please add both secrets, your username and password.

Your dev branch should now be set up to automatically push to Dockerhub.