How to Configure Apache as a Reverse Proxy with mod_proxy

Introduction

Apache is a web server application that can serve dynamic web content or act as a reverse proxy —forwarding client requests to back-end applications. This article explains how to configure Apache to work as a reverse proxy with mod_proxy.

This guide proxies an ownCloud application on port 8080 under Docker, but you can use the same technique to host another application on a different port.

Prerequisites

• Deploy a fresh Vultr Cloud Server.

A Ubuntu 20.04 server is used in this article, but these instructions work for any Linux server running Apache.

• Set up a DNS "A" record pointing to the server's IP address. This guide uses the name app.example.com.
• Connect to the server.
• Log in as a non-root user with sudo privileges.
• Update the server.
• Install Apache.
• Install Docker.

1. Enable mod_Proxy

1. Enable the Apache mod_proxy module.

     $ sudo a2enmod proxy

2. Enable additional modules.

     $ sudo a2enmod proxy_http
     $ sudo a2enmod proxy_balancer
     $ sudo a2enmod proxy_wstunnel

   Here is what each module does:

   • mod_proxy: Implements proxying on the Apache server.
   • proxy_http: Handles proxy HTTP and HTTPS requests.
   • proxy_balancer: Enables load balancing.
   • proxy_wstunnel: Tunnels web socket connections to a back-end server.

3. Restart Apache to activate modules.

     $ sudo systemctl restart apache2

2. Set up the Back-end Application

As an example, set up an ownCloud container listening on port 8080 under Docker.

1. Create the ownCloud docker container.

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

2. Start ownCloud.

     $ docker start owncloud

3. Verify that ownCloud is running.

     $ docker ps

   Output:

     CONTAINER ID   IMAGE             COMMAND                  CREATED          STATUS          PORTS                                       NAMES
     3eaea7b55cfe   owncloud/server   "/usr/bin/entrypoint…"   36 seconds ago   Up 35 seconds   0.0.0.0:8080->8080/tcp, :::8080->8080/tcp   owncloud

3. Setup Apache as a Reverse Proxy

1. Back up the default Apache virtual host configuration file.

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

2. Create a new configuration file.

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

3. Add the following contents to the file. Change app.example.com to your server name. If you are setting up a proxy for a different app than the ownCloud example, you may need to update port 8080 to your application's port number in the file below.

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

4. Save and close the file.

   Here is what each directive means:

   • ProxyPreserveHost: Forwards the original host header to the back-end application.
   • ProxyPass: Specifies that all requests / are forwarded to the back-end application port.
   • ProxyPassReverse: Negates ProxyPass by modifying response headers from the back-end application.

5. Activate the configuration file.

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

6. Test the Apache configuration for errors.

     $ sudo apachectl configtest

7. Restart Apache to load changes.

     $ sudo service apache2 restart

4. Secure the server

1. Configure the firewall to allow HTTP traffic on port 80.

     $ sudo ufw allow 80/tcp

2. Allow HTTPS on port 443.

     $ sudo ufw allow 443/tcp

3. Restart the firewall.

     $ sudo ufw reload

5. Setup SSL

1. Install Certbot.

     $ sudo apt install certbot python3-certbot-apache

2. Request a Let's Encrypt SSL Certificate.

     $ sudo certbot -d app.example.com

3. Test Auto-renewal.

     $ sudo certbot renew --dry-run

6. Test

Open a web browser, and visit your subdomain.

     https://app.example.com

The ownCloud login page should be displayed. Log in with the username admin, and password admin to start using the application.

More Information

You have configured Apache as a reverse proxy and set up ownCloud as the back-end application. For further information, refer to the following resources.

• Apache mod_proxy documentation.
• Use Apachetop To Monitor Web Server Traffic In Real Time.
• Secure Apache with a Self-Signed TLS/SSL Certificate on Ubuntu 20.04.