How to Configure Apache as a Reverse Proxy with mod_proxy

Apache is a powerful and versatile web server that can also act as a reverse proxy, forwarding client requests to backend servers. Setting up Apache as a reverse proxy enhances security, simplifies client access to multiple services, and improves load balancing. Here’s a simplified guide to configure Apache as a reverse proxy using the mod_proxy module.

What You’ll Need #

1. A fresh Linux server (e.g., Ubuntu 20.04) with Apache installed.
2. A DNS “A” record pointing to your server’s IP (e.g., app.example.com).
3. Docker installed to host backend applications like ownCloud.
4. A non-root user with sudo privileges.

Step 1: Enable Required Modules #

Apache uses several modules for reverse proxying. Start by enabling these:

sudo a2enmod proxy
sudo a2enmod proxy_http
sudo a2enmod proxy_balancer
sudo a2enmod proxy_wstunnel

• mod_proxy: Core proxying functionality.
• proxy_http: Handles HTTP/HTTPS requests.
• proxy_balancer: Adds load-balancing capabilities.
• proxy_wstunnel: Facilitates WebSocket tunneling.

Restart Apache to apply changes:

sudo systemctl restart apache2

Step 2: Set Up a Backend Application #

For this example, we’ll use ownCloud hosted in a Docker container:

docker run -d --name owncloud -p 8080:8080 owncloud/server
docker start owncloud

Verify that ownCloud is running:

docker ps

Step 3: Configure Apache as a Reverse Proxy #

Back Up the Default Configuration:

sudo mv /etc/apache2/sites-available/000-default.conf /etc/apache2/sites-available/origdefault.backup

Create a New Configuration File:

sudo nano /etc/apache2/sites-available/app.example.com.conf

Add the following content, replacing app.example.com with your domain:

<VirtualHost *:80>
    ServerName app.example.com
    ProxyPreserveHost On
    ProxyPass / http://127.0.0.1:8080/
    ProxyPassReverse / http://127.0.0.1:8080/
</VirtualHost>

• ProxyPreserveHost: Forwards the original host header to the backend.
• ProxyPass: Routes client requests to the backend server.
• ProxyPassReverse: Adjusts response headers from the backend.

Activate the Configuration:

sudo ln -s /etc/apache2/sites-available/app.example.com.conf /etc/apache2/sites-enabled/app.example.com.conf

Test and Restart Apache:

sudo apachectl configtest
sudo systemctl restart apache2

Step 4: Secure the Server #

Allow HTTP and HTTPS traffic:

sudo ufw allow 80/tcp
sudo ufw allow 443/tcp
sudo ufw reload

Install SSL certificates for secure connections:

sudo apt install certbot python3-certbot-apache

sudo certbot -d app.example.com

Test automatic SSL renewal:

sudo certbot renew --dry-run

Step 5: Verify the Setup #

Open a browser and navigate to https://app.example.com. If everything is configured correctly, you’ll see the backend application’s interface (e.g., ownCloud login page).

Benefits of Using Apache as a Reverse Proxy #

• Improved Security: Shields backend servers from direct exposure.
• Centralized Access: Simplifies client access to multiple services.
• Load Balancing: Distributes traffic effectively.
• Flexibility: Supports various backend applications.

By following these steps, you’ve successfully set up Apache as a reverse proxy with mod_proxy, providing a robust and secure infrastructure for your applications.