CircleCI Mono Repo Setup

config.yml

version: 2.1

# Use CircleCI's dynamic configuration feature
setup: true

# Orbs are built in helpers made by CircleCI & the community 
orbs:
  # Path iltering is the magic behind checking for file changes and leverages continuation orb to proceed with workflows
  path-filtering: circleci/path-filtering@0.0.2 

# Executors are used for jobs, options to what docker image is used for each 
executors:
  alpine-git:
    docker:
      - image: alpine/git:v2.30.2

# Jobs to be wired into a workflow, each job can have many steps
jobs:
  update-mirror-repository:
    executor: alpine-git
    steps:
      - checkout
      - add_ssh_keys: 
          fingerprints:
            - "ADD SSH KEY FINGERPRINT OF MIRROR REMOTE REPO" #https://circleci.com/docs/2.0/add-ssh-key/
      - run:
          name: Update Mirrored Repository
          command: |
            git remote add d3vadv3ntur3s-mirror git@github.com:d3vadv3ntur3s/d3vadv3ntur3s-mirror-project.git
            git push --mirror d3vadv3ntur3s-mirror


workflows:
  # Runs the two following jobs everytime 
  setup-workflow:
    jobs:
      - update-mirror-repository
      - path-filtering/filter:
          mapping: |
            backend/.* run-backend true
            frontend/.* run-frontend true
          # Compares differences to main branch
          base-revision: main
          config-path: .circleci/workflows.yml

workflows.yml

version: 2.1

# the default pipeline parameters, which will be updated according to the results of the path-filtering orb
parameters:
  run-backend:
    type: boolean
    default: false
  run-frontend:
    type: boolean
    default: false

executors:
  node:
    docker:
      - image: cimg/node:16.5.0
  dind:
    docker:
      - image: cimg/base:2021.07


jobs:
  backend-unit-test:
    executor: node
    working_directory: ~/monorepo/backend
    steps:
      - checkout:
          path: ~/monorepo
      - restore_cache:
          key: backend-dependency-cache-{{ checksum "package-lock.json" }}
      - run:
          name: Install Dependencies
          command: npm ci
      - save_cache:
          key: backend-dependency-cache-{{ checksum "package-lock.json" }}
          paths:
            - node_modules
      - run:
          name: Run Linter
          command: npm run lint
      - run:
          name: Backend Unit Test 
          command: npm test
  backend-build:
    executor: dind
    working_directory: ~/monorepo/backend
    steps:
      - checkout:
          path: ~/monorepo
      - setup_remote_docker:
          version: 20.10.6
      - run: |
          source ./aws_credentials
          DOCKER_BUILDKIT=1 docker build --secret id=npmrc,src=.npmrc -t monorepo/backend:$CIRCLE_SHA1 .
          docker tag monorepo/backend:$CIRCLE_SHA1 AWS_ACCOUNT_ID_HERE.dkr.ecr.eu-west-1.amazonaws.com/monorepo/backend:$CIRCLE_SHA1
          aws ecr get-login-password --region eu-west-1 | docker login --username AWS --password-stdin "AWS_ACCOUNT_ID_HERE.dkr.ecr.eu-west-1.amazonaws.com"
          docker push "AWS_ACCOUNT_ID_HERE.dkr.ecr.eu-west-1.amazonaws.com/monorepo/backend:$CIRCLE_SHA1"
# OMMITED Other steps for sake of brevity, i.e. not included frontend jobs, creds, deployment      

# Workflow is decided based on the parameters, triggered from the config.yml based on file changes to frontend or backend
workflows:
  backend:
    when: << pipeline.parameters.run-backend >>
    jobs:
      - backend-unit-test:
          name: unit-tests
      - backend-build:
          filters:
            branches:
              only: main
  frontend:
    when: << pipeline.parameters.run-frontend >>
    jobs:
      - frontend-unit-test:
          name: unit-tests
      - frontend-build:
          filters:
            branches:
              only: main
      

Useful CircleCI Docs: https://circleci.com/docs/2.0/configuration-cookbook/?section=examples-and-guides#execute-specific-workflows-or-steps-based-on-which-files-are-modified

Useful API Docs : https://circleci.com/docs/api/v2/