Creating a GitHub repository – Continuous Integration with GitHub Actions and Jenkins-1

Before we can use GitHub Actions, we need to create a GitHub repository. As we know that each microservice can be independently developed, we will place all of them in separate Git repositories. For this exercise, we will focus only on the posts microservice and leave the rest to you as an exercise.

To do so, go to https://github.com/new and create a new repository. Give it an appropriate name. For this exercise, I am going to use mdo-posts.

Once you’ve created it, clone the repository by using the following command:

$ git clone https://github.com/<GitHub_Username>/mdo-posts.git

Then, change the directory into the repository directory and copy the app.py, app.test. py, requirements.txt, and Dockerfile files into the repository’s directory using the following commands:

$ cd mdo-posts

$ cp ~/modern-devops/blog-app/posts/* .

Now, we need to create a GitHub Actions workflow file. We’ll do this in the next section.

Creating a GitHub Actions workflow

A GitHub Actions workflow is a simple YAML file that contains the build steps. We must create this workflow in the .github/workflows directory within the repository. We can do this using the following command:

$ mkdir -p .github/workflows

We will use the following GitHub Actions workflow file, build.yaml, for this exercise:

name: Build and Test App
on:
push:
branches: [ main ]
pull_request:
branches: [ main ]
jobs:
build:
runs-on: ubuntu-latest
steps:
uses: actions/checkout@v2
name: Login to Docker Hub
id: login
run: docker login -u ${{ secrets.DOCKER_USER  }} -p ${{ secrets.DOCKER_PASSWORD }}
name: Build the Docker image
id: build
run: docker build . –file Dockerfile –tag ${{ secrets.DOCKER_USER  }}/
mdo-posts:$(git rev-parse –short “$GITHUB_SHA”)

• name: Push the Docker image
  id: push
  run: docker push ${{ secrets.DOCKER_USER }}/mdo-posts:$(git rev-parse –short “$GITHUB_SHA”)

This file comprisesthe following:

•    name: The workflow’s name – Build and Test App in this case.

• on: This describes when this workflow will run. In this case, it will run if apush or pull request is sent on the main branch.

• jobs: A GitHub Actions workflow contains one or more jobs that run in parallel by default. This attribute includes all jobs.

• jobs.build: This is a job that does the container build.

• jobs.build.runs-on: This describes where the build job will run. We’ve specified ubuntu-latest here. This means that this job will run on an Ubuntu VM.

• jobs.build.steps: This consists of the steps that run sequentially within the job. The

build job consists of four build steps: checkout, which will check out the code from your repository; login, which will log in to Docker Hub; build, which will run a Docker build on your code; and push, which will push your Docker image to Docker Hub. Note that we tag the image with the Git commit SHA. This relates the build with the commit, making Git the single source of truth.

• jobs.build.steps.uses: This is the first step and describes an action you will run as a part of your job. Actions are reusable pieces of code that you can execute in your pipeline. In this case, it runs the checkout action. It checks out the code from the current branch where the action is triggered.

Tip

Always use a version with your actions. This will prevent your build from breaking if a later version is incompatible with your pipeline.

• jobs.build.steps.name: This is thename of your build step.

• jobs.build.steps.id: This is the unique identifier of your build step.

• jobs.build.steps.run: This is the command it executes as part of the build step.

The workflow also contains variables within ${{ }} . We can define multiple variables within the workflow and use them in the subsequent steps. In this case, we’ve used two variables – ${{ secrets.DOCKER_USER }} and ${{ secrets.DOCKER_PASSWORD }}. These variables are sourced from GitHub secrets.

Tip

It is best practice to use GitHub secrets to store sensitive information. Never store these details directly in the repository with code.