Deploying Flask Applications on AWS EC2

Deploying a Flask application properly is crucial for ensuring your web application runs efficiently and securely in a production environment. This guide will walk you through the process of deploying a Flask application on AWS EC2 using Gunicorn as the WSGI server and Nginx as the reverse proxy.

Prerequisites

• An AWS account
• Basic knowledge of command line and SSH
• A Flask application ready for deployment
• Understanding of Python virtual environments

1. Launch an EC2 Instance

First, we'll need to set up our EC2 instance:

• Sign in to AWS Management Console
• Navigate to EC2 Dashboard
• Click "Launch Instance"
• Choose Ubuntu Server 20.04 LTS (or newer)
• Select t2.micro (free tier eligible)
• Configure security group to allow HTTP (80), HTTPS (443), and SSH (22)
• Create or select an existing key pair for SSH access

2. Connect to Your Instance

Once your instance is running, connect to it via SSH:

ssh -i /path/to/your-key.pem ubuntu@your-public-ip

3. Install Required Packages

Update your system and install necessary dependencies:

sudo apt update
sudo apt upgrade -y
sudo apt install python3 python3-pip python3-venv nginx git -y

4. Set Up Your Application

Clone your application repository and set up a virtual environment:

cd ~
git clone https://github.com/yourusername/your-repo.git
cd your-repo
python3 -m venv .venv
source .venv/bin/activate
pip install -r requirements.txt
pip install gunicorn

5. Configure Gunicorn

Create a systemd service file for Gunicorn to run your application:

sudo nano /etc/systemd/system/myflaskapp.service

Add the following configuration:

[Unit]
Description=Gunicorn instance for myflaskapp
After=network.target

[Service]
User=ubuntu
Group=www-data
WorkingDirectory=/home/ubuntu/your-repo
Environment="PATH=/home/ubuntu/your-repo/.venv/bin"
ExecStart=/home/ubuntu/your-repo/.venv/bin/gunicorn --workers 3 --bind unix:myflaskapp.sock -m 007 app:app

[Install]
WantedBy=multi-user.target

6. Configure Nginx

Create an Nginx configuration file for your application:

sudo nano /etc/nginx/sites-available/myflaskapp

Add the following configuration:

server {
    listen 80;
    server_name your-public-ip;

    location / {
        proxy_pass http://unix:/home/ubuntu/your-repo/myflaskapp.sock;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto $scheme;
    }
}

7. Enable and Start Services

Link the Nginx configuration and start all services:

sudo ln -s /etc/nginx/sites-available/myflaskapp /etc/nginx/sites-enabled
sudo nginx -t
sudo systemctl restart nginx
sudo systemctl start myflaskapp
sudo systemctl enable myflaskapp
sudo systemctl status myflaskapp

8. Verify Deployment

Your Flask application should now be running. Test it by accessing your EC2 instance's public IP address in a web browser.

Troubleshooting Common Issues

• 502 Bad Gateway: Check Gunicorn service status and logs
• Permission errors: Ensure proper file permissions and ownership
• Socket file not found: Verify the socket file path in both Gunicorn and Nginx configs

Conclusion

Your Flask application should now be running on your EC2 instance. Remember to:

• Set up HTTPS using Let's Encrypt for production (covered in next article)
• Implement proper monitoring and logging
• Regularly update your packages and security groups
• Back up your application and data regularly
• Configure environment variables for sensitive data