CI & CD for a Django Application on Kubernetes using Gitlab CI

# Gitlab CI yml file
# GitLab CI uses the services keyword to define what docker containers should be linked with your base image. Since we are using docker as our image we'll be using docker:dind i.e. Docker-In-Docker-Image
services:
- docker:dind

# Since we are using Alpine, everything is not installed by default.
# Thus we are setting up the basics
before_script:
  - apk update && apk upgrade && apk add --no-cache bash openssh
  
# Environemt Variable for docker:dind service explaining to use overlay2 as supporting driver for docker
variables:
  DOCKER_DRIVER: overlay2

# This is the major part of the code which explains the stages present in our pipeline.
# In a django application we have various stages which include testing, packing the code,
# performing migrations, collecting static files and running the application.
# The various stages are broadly classified into 3 main categories:

# 1. Test       2. Release      3. Deploy

stages:
- test
- release
- deploy

# Stage I
# Testing Phase:
# This is where the main code is tested.
# Other options like code coverage, etc are also written in this phase
test:
  stage: test
  # This repo includes python3, pip3 and postgres so that I need not
  # setup python and postgres separately.
  image: vaeum/alpine-python3-pip3
  before_script:
    # Installing requirements
    - pip install -r requirements.txt
  variables:
    # Connecting to testDB
    POSTGRES_DB: postgres
    POSTGRES_USER: postgres
    POSTGRES_PASSWORD: ''
    POLLSAPI_PG_HOST: postgres
  services:
    - postgres:9.6-alpine
  script:
    # Command to test our application
    - python manage.py test

# Stage II
# Release Phase
# In this phase, we package our code using docker
# as we deploy containerized applications on kubernetes
release:
  stage: release
  image: docker:latest
  before_script:
   # Note the image in L#69 being a docker image. This is because in release we
   # need to package our application using docker and login so that we'll be able
   # to push our images to Google Container Registry

   # Pre-requisites required to install google cloud sdk on gitlab runner
   - export COMMIT_SHA=$(echo $CI_COMMIT_SHA | cut -c1-8)
   - apk update
   - apk upgrade
   - apk add python python-dev py-pip build-base 
   - apk add --update ca-certificates
   - apk add --update -t deps curl
   - apk del --purge deps
   - rm /var/cache/apk/*

  script:
    # Build our image using docker
    - docker build -t $GCP_PROJECT_ID/$CI_PROJECT_NAME:$COMMIT_SHA .

    # Write our GCP service account private key into a file
    - echo $GCLOUD_SERVICE_KEY | base64 -d > ${HOME}/gcloud-service-key.json
    
    # Download and install Google Cloud SDK
    - wget https://dl.google.com/dl/cloudsdk/release/google-cloud-sdk.tar.gz
    - tar zxvf google-cloud-sdk.tar.gz && ./google-cloud-sdk/install.sh --usage-reporting=false --path-update=true
    
    # Update gcloud components
    - google-cloud-sdk/bin/gcloud --quiet components update

    # Give access to gcloud project
    - google-cloud-sdk/bin/gcloud auth activate-service-account --key-file ${HOME}/gcloud-service-key.json  || die "unable to authenticate service account for gcloud"
    
    # Get current projects credentials to access it
    - google-cloud-sdk/bin/gcloud container clusters get-credentials pollsapi --zone asia-south1-a --project test-gcp-208915
    
    # Configure container registry to push using docker
    - docker login -u _json_key --password-stdin https://gcr.io < ${HOME}/gcloud-service-key.json

    # Push the image using docker
    - docker push $GCP_PROJECT_ID/$CI_PROJECT_NAME:$COMMIT_SHA

    # The tag, only master indicates that whenever code is pushed to master branch,
    # only then run the pipeline
  environment: production
  only:
    - master

# Stage III - I
# Deployment Phase
# In this phase, migrations are performed.
# Note that this is a manual stage as migrations are not run for each commit.
# If needed to run for every merge/commit to master branch, then comment when:manual
migrations:
  image: google/cloud-sdk:alpine
  stage: deploy
  variables:
    KUBE_LATEST_VERSION: "v1.8.5"
  before_script:
   # Pre-requisites required to install kybectl command line on gitlab runner
   - export COMMIT_SHA=$(echo $CI_COMMIT_SHA | cut -c1-8)
   - apk update
   - apk upgrade
   - apk add --update ca-certificates
   - apk add --update -t deps curl
   - curl -L https://storage.googleapis.com/kubernetes-release/release/${KUBE_LATEST_VERSION}/bin/linux/amd64/kubectl -o /usr/local/bin/kubectl
   - chmod +x /usr/local/bin/kubectl
   - apk del --purge deps
   - rm /var/cache/apk/*

  script:
    # Write our GCP service account private key into a file
    - echo $GCLOUD_SERVICE_KEY | base64 -d > ${HOME}/gcloud-service-key.json
    
    # Update gcloud components
    - gcloud --quiet components update

    # Give access to gcloud project
    - gcloud auth activate-service-account --key-file ${HOME}/gcloud-service-key.json  || die "unable to authenticate service account for gcloud"
    - gcloud container clusters get-credentials pollsapi --zone asia-south1-a --project test-gcp-208915
    
    # Update the image tag inside the file polls-migration.yml using sed
    - sed -i 's/${TAG}/'"$COMMIT_SHA"'/g' polls-migration.yml

    # Run kubectl apply to apply any changes made in env variables, etc
    - kubectl apply -f polls-migration.yml
  environment: production
  
  # Note that when: manual indicates that this is a manual action
  # and will only trigger if they user clicks play button, in the pipeline
  when: manual
  only:
    - master

# Stage III - II
# Deployment Phase
# In this phase we will be collecting static files.
# Usually collecting static files is a one time operation and is 
# not done every time. For this reason this has been made a manual branch
# meaning, it has to be triggered manually whenever required
collect-static:
  image: google/cloud-sdk:alpine
  stage: deploy
  variables:
    KUBE_LATEST_VERSION: "v1.8.5"
  before_script:
   # Pre-requisites required to install kybectl command line on gitlab runner
   - export COMMIT_SHA=$(echo $CI_COMMIT_SHA | cut -c1-8)
   - apk update
   - apk upgrade
   - apk add --update ca-certificates
   - apk add --update -t deps curl
   - curl -L https://storage.googleapis.com/kubernetes-release/release/${KUBE_LATEST_VERSION}/bin/linux/amd64/kubectl -o /usr/local/bin/kubectl
   - chmod +x /usr/local/bin/kubectl
   - apk del --purge deps
   - rm /var/cache/apk/*

  script:
    # Write our GCP service account private key into a file
    - echo $GCLOUD_SERVICE_KEY | base64 -d > ${HOME}/gcloud-service-key.json
    
    # Update gcloud components
    - gcloud --quiet components update

    # Give access to gcloud project
    - gcloud auth activate-service-account --key-file ${HOME}/gcloud-service-key.json  || die "unable to authenticate service account for gcloud"
    - gcloud container clusters get-credentials pollsapi --zone asia-south1-a --project test-gcp-208915
    
    # Update the image tag inside the file polls-collect-static.yml using sed
    - sed -i 's/${TAG}/'"$COMMIT_SHA"'/g' polls-collect-static.yml

    # Run kubectl apply to apply any changes made in env variables, etc
    - kubectl apply -f polls-collect-static.yml
  environment: production
  when: manual
  only:
    - master

# Stage III - III
# Deployment Phase
# In this phase, we make sure to update our application based on
# the data in current commit and mainly focus on application deployment.
deploy:
  image: google/cloud-sdk:alpine
  stage: deploy
  variables:
    KUBE_LATEST_VERSION: "v1.8.5"
  before_script:
   # Pre-requisites required to install kybectl command line on gitlab runner
   - export COMMIT_SHA=$(echo $CI_COMMIT_SHA | cut -c1-8)
   - apk update
   - apk upgrade
   - apk add --update ca-certificates
   - apk add --update -t deps curl
   - curl -L https://storage.googleapis.com/kubernetes-release/release/${KUBE_LATEST_VERSION}/bin/linux/amd64/kubectl -o /usr/local/bin/kubectl
   - chmod +x /usr/local/bin/kubectl
   - apk del --purge deps
   - rm /var/cache/apk/*

  script:
    # Write our GCP service account private key into a file
    - echo $GCLOUD_SERVICE_KEY | base64 -d > ${HOME}/gcloud-service-key.json
    
    # Update gcloud components
    - gcloud --quiet components update

    # Give access to gcloud project
    - gcloud auth activate-service-account --key-file ${HOME}/gcloud-service-key.json  || die "unable to authenticate service account for gcloud"
    - gcloud container clusters get-credentials pollsapi --zone asia-south1-a --project test-gcp-208915
    
    # Run kubectl apply to apply any changes made in env variables, etc
    - kubectl apply -f pollsapi.yml

    # Update deployment with new image
    - kubectl set image deployment/polls-api ${CI_PROJECT_NAME}=$GCP_PROJECT_ID/$CI_PROJECT_NAME:$COMMIT_SHA
  environment: production
  only:
    - master