Local Development

Start a local Redis server:

docker run --name redis -p 6379:6379 -d redis:latest

Install Python and Environment:

python3.10 -m venv env
source env/bin/activate
pip install -r requirements.txt

Test Application:

flake8 --exclude=env/ . -v 
pytest tests.py

Run Flask Application

flask run

The Source code of the Flask Application and the Dockerfile should not be taken as examples on how to write a Flask Application or how to write a Dockerfile. The Flask Application and the Dockerfile are only there to show how to set up a CI/CD pipeline with GitLab.

Local Setup with Docker

It's possible to manually set up the Docker containers locally:

# Create .env file
echo "REDIS_HOST=redis" > .env

# Set up Docker containers
docker network create example_network
docker build -t example .
docker run --name example --network example_network -p 5000:5000 -d example
docker run --name redis -p 6379:6379 --network example_network -d redis:latest

# Tear down Docker containers
docker stop example
docker rm example
docker stop redis
docker rm redis
docker network rm example_network
rm .env

Local Setup with Docker Compose

It's also possible to use Docker Compose to set up the Docker containers locally:

First you need to uncomment the build option and comment the image option in the docker-compose.yml file.

  flask:
    build: .
    # image: ${TAG_COMMIT}

Then you can run the following commands:

docker compose build
docker compose up -d

Environment Variables for CI/CD

REDIS_HOST (should be set to "redis" for all)
REDIS_PORT (should be set to "6379" for all)
REDIS_PASSWORD (should only be set for deployment environment)

SERVER_RSA (file) (SSH key to connect to respective deployment environment)
SERVER_USER (SSH user to connect to respective deployment environment)

Also, a file environment CI/CD Variable should be created, which pulls together the Redis Variables:

REDIS_HOST=$REDIS_HOST
REDIS_PORT=$REDIS_PORT
REDIS_PASSWORD=$REDIS_PASSWORD

The option "Expand variable reference" should be checked for this file.

CI

Make changes, push to the main branch and the flake8 and pytest tests will run automatically.

or

Go to the Build-> Pipelines page and press the button Run Pipeline. Then select the main branch and press the button Run Pipeline.

Environments for CD

For the deployment a <name>-environment branch should be created. As well as under operate -> Environments a new environment should be created with the name <name>-environment and the server http address for deployment.

CD

Make changes, push to the main branch, merge those changes to the <name>-environment branch, and the changes will be deployed to the VM automatically.

or

Go to the Build-> Pipelines page and press the button Run Pipeline. Then select the <name>-environment branch and press the button Run Pipeline.

or

Go to Operate -> Environments -> <name>-environment and select the commit to redeploy / rollback. This is only possible if the commit was deployed successfully before.