CI/CD Pipeline for a Flask Application

This project implements a complete CI/CD (Continuous Integration/Continuous Deployment) pipeline for a simple web application written in Python using the Flask framework. The main goal is to demonstrate key DevOps skills, including automation, containerization, and deployment management.

The entire process, from fetching the code to the final deployment, is automated by Jenkins using the Pipeline as Code concept (Jenkinsfile).

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Project Architecture

The architecture is simple yet effective. The end-user accesses the application through the Nginx web server, which acts as a reverse proxy, forwarding traffic to the Docker container where the Flask app is running. +-----------------+ +-------------------------+ +---------------------------------+ | User/Browser |----->| Debian VM (Port 80) |----->| Docker Container (Port 5000) | | | | +---------------------+ | | +-----------------------------+ | | | | | Nginx | | | | Flask App | | | | | | (Reverse Proxy) | | | | | | | | | +---------------------+ | | +-----------------------------+ | +-----------------+ +-------------------------+ +---------------------------------+

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Technologies Used

• CI/CD Server: Jenkins
• Containerization: Docker
• Web Server / Reverse Proxy: Nginx
• Application Framework: Python (Flask)
• Infrastructure: Debian 12 Virtual Machine
• Version Control: Git & GitHub
• Scripting: Groovy (for Jenkinsfile) and Bash

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Key Features

• Full Automation: The pipeline automatically fetches the code, builds a new Docker image, and updates the application upon execution.
• Pipeline as Code: All pipeline stages are defined in a Jenkinsfile, which is version-controlled alongside the application code.
• Zero-Downtime Deployment Strategy: By stopping the old container and immediately replacing it with the new one, downtime is minimized.
• Isolated & Portable Environment: Using Docker ensures that the application and its dependencies run in an isolated and portable environment.

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Pipeline Stages (Jenkinsfile)

The pipeline is defined with the following core stages:

1. Build Docker Image:

   • In this stage, Jenkins uses the Dockerfile in the project root to build a new application image.
   • To avoid conflicts, each new image is tagged with the unique Jenkins build number (e.g., python-flask-app:1, python-flask-app:2).

2. Deploy Application:

   • First, the previously running container (if it exists) is stopped using docker stop.
   • It is then removed with docker rm.
   • Finally, a new container is started in detached mode (-d) from the image created in the previous stage.

3. Post Actions (Cleanup):

   • After the pipeline finishes (on success or failure), the docker image prune command is executed to remove any dangling images, preventing disk space from filling up.