Github Actions: Build Multiple docker images in Mono Repo

Learn how to build multiple Docker images for a single repository using matrix builds with Github Actions in this comprehensive tutorial. Dockerizing applications is a powerful way to deploy them, and Github Actions provides an easy way to build and push Docker images to a registry. Follow along as we demonstrate how to use matrix builds to build multiple Docker images for a single repository with Github Actions

Building a single docker image

For this example, we will use the Build and Push Docker Images action from the Github Marketplace. The action is very simple to use. You only need to specify the Docker registry, the username and password.

name: ci

on:
  push:
    branches:
      - 'main'

jobs:
  docker:
    runs-on: ubuntu-latest
    steps:
      -
        name: Checkout
        uses: actions/checkout@v3
      -
        name: Login to Docker Hub
        uses: docker/login-action@v2
        with:
          username: ${{ secrets.DOCKERHUB_USERNAME }}
          password: ${{ secrets.DOCKERHUB_TOKEN }}
	   -
        name: Docker meta
        id: meta
        uses: docker/metadata-action@v4
        with:
          images: your-docker-registry/app1
      -
        name: Build and push
        uses: docker/build-push-action@v4
        with:
          push: true
          tags: user/app:latest

This will use the Dockerfile in the root of the repository to build the docker image and push it to the Docker Hub registry.

Building multiple docker images

Now we are going to build multiple docker images for a single repository. We will use the same action as before, but we will use a matrix build to build multiple docker images.

Matrix builds allow you to run the same job multiple times with different parameters. In our case, we will use the matrix to build multiple docker images.

name: ci
on:
  push:
    branches:
      - 'main'

jobs:
  docker:
    runs-on: ubuntu-latest
	strategy:
	  matrix:
		include:
		  - image: your-docker-registry/app1
		    dockerfile: app1/Dockerfile
		  - image: user/app2
		    dockerfile: your-docker-registry/app1
    steps:
      -
        name: Checkout
        uses: actions/checkout@v3
      -
        name: Login to Docker Hub
        uses: docker/login-action@v2
        with:
          username: ${{ secrets.DOCKERHUB_USERNAME }}
          password: ${{ secrets.DOCKERHUB_TOKEN }}
	  - 
	    name: Extract metadata (tags, labels) for Docker
        id: meta
        uses: docker/metadata-action@v4
        with:
          images: ${{ matrix.image }}
      -
        name: Build and push
        uses: docker/build-push-action@v4
       	with:
          context: .
          file: ${{ matrix.dockerfile }}
          push: true
          tags: ${{ steps.meta.outputs.tags }}
          labels: ${{ steps.meta.outputs.labels }

This will build two docker images. One for your-docker-registry/app1 and one for your-docker-registry/app2. The Dockerfile for your-docker-registry/app1 is located in the app1 folder. The Dockerfile for your-docker-registry/app2 is located in the root of the repository.