Setting Up a CI/CD Pipeline for a Flask Application on AWS

In today's fast-paced software development landscape, Continuous Integration (CI) and Continuous Deployment (CD) have become essential practices for delivering robust applications. Implementing a CI/CD pipeline for a Flask application on AWS not only streamlines your development process but also enhances collaboration and efficiency. This article will guide you through the setup of a CI/CD pipeline tailored for a Flask app, ensuring you have the tools and knowledge to automate your deployment processes effectively.

Understanding CI/CD

Before diving into the setup, let’s clarify what CI/CD means:

• Continuous Integration (CI): The practice of automatically testing and merging code changes into a shared repository. CI helps catch bugs early by running automated tests on new code.

• Continuous Deployment (CD): The process of automatically deploying code changes to production after passing predefined tests, ensuring that your application is always up-to-date.

Why Use CI/CD for Flask Applications?

• Faster Development Cycle: Automating testing and deployment allows developers to focus more on coding rather than manual processes.

• Improved Code Quality: Automated tests help ensure that new code does not break existing functionality.

• Scalability: A CI/CD pipeline can easily scale as your application grows, accommodating more developers and features.

Prerequisites

Before setting up your CI/CD pipeline, ensure you have the following:

• An AWS account
• Basic knowledge of Flask and Python
• Familiarity with Git
• AWS CLI installed and configured

Setting Up Your Flask Application

If you haven’t yet created a Flask application, start by setting one up. Here’s a simple example:

Step 1: Create a Basic Flask App

# app.py
from flask import Flask

app = Flask(__name__)

@app.route('/')
def home():
    return "Hello, Flask CI/CD!"

if __name__ == '__main__':
    app.run(debug=True)

Step 2: Create a Requirements File

List your application’s dependencies in a requirements.txt file:

Flask==2.0.2

Setting Up AWS Services

To deploy your Flask application, you’ll need to use several AWS services:

• AWS CodeCommit: A fully managed source control service.
• AWS CodeBuild: A fully managed build service.
• AWS CodeDeploy: A deployment service that automates application deployment to various compute services.
• AWS Elastic Beanstalk: An easy-to-use service for deploying and scaling web applications.

Step 3: Create a CodeCommit Repository

1. Log in to the AWS Management Console.
2. Navigate to CodeCommit and create a new repository.
3. Clone the repository to your local machine:

git clone https://git-codecommit.<region>.amazonaws.com/v1/repos/<repo-name>
cd <repo-name>

1. Copy your Flask app files into this directory and commit:

git add .
git commit -m "Initial commit"
git push

Step 4: Create a Buildspec File

Create a buildspec.yml file in your repository root. This file defines the build commands and settings for CodeBuild:

version: 0.2

phases:
  install:
    runtime-versions:
      python: 3.x
    commands:
      - pip install -r requirements.txt
  build:
    commands:
      - echo Build started on `date`
      - echo Building the Flask application...
  post_build:
    commands:
      - echo Build completed on `date`

Step 5: Create a CodeBuild Project

1. Go to CodeBuild in the AWS Management Console.
2. Create a new build project:
3. Source: Choose the CodeCommit repository you created.
4. Environment: Use a managed image and select an appropriate runtime.
5. Buildspec: Choose “Use the buildspec.yml in the source code root.”

Step 6: Configure CodeDeploy

1. Go to CodeDeploy and create a new application.
2. Choose “EC2/On-Premises” as the compute platform.
3. Create a deployment group, selecting the EC2 instances where your Flask app will run.

Step 7: Create an AppSpec File

Create an appspec.yml file to define how CodeDeploy should deploy your application:

version: 0.0
os: linux
files:
  - source: /
    destination: /var/www/myflaskapp
hooks:
  AfterInstall:
    - location: scripts/start_server.sh
      timeout: 300
      runas: root

Step 8: Create a Deployment Script

Create a scripts/start_server.sh file to start your Flask application:

#!/bin/bash
cd /var/www/myflaskapp
source venv/bin/activate
nohup python app.py > app.log 2>&1 &

Make sure to give it execute permissions:

chmod +x scripts/start_server.sh

Integrating CI/CD

Step 9: Set Up AWS CodePipeline

1. Go to CodePipeline in the AWS Management Console.
2. Create a new pipeline:
3. Source provider: Choose CodeCommit.
4. Build provider: Choose CodeBuild.
5. Deploy provider: Choose CodeDeploy.

Step 10: Test Your CI/CD Pipeline

Commit a change to your Flask application and push it to your CodeCommit repository. This should trigger the CI/CD pipeline, which will build and deploy your application automatically.

Troubleshooting Common Issues

• Build Failures: Check the logs in CodeBuild for any errors during the build process.
• Deployment Issues: Review the logs in CodeDeploy to identify any problems during the deployment.

Conclusion

Setting up a CI/CD pipeline for your Flask application on AWS enhances your development workflow, enabling you to deploy faster and more reliably. By following the steps outlined in this article and leveraging AWS services, you can create a robust pipeline that supports continuous integration and deployment, ensuring your application remains up-to-date and high-quality. Embrace the power of CI/CD and watch your development process transform!