How to Configure Apache as a Reverse Proxy

Apache as a reverse proxy directs requests to backend servers. Proper ProxyPassReverse and ProxyPreserveHost configuration prevents header rewriting issues. This guide walks through the specific troubleshooting steps to diagnose and resolve reverse proxy issues.

Before You Begin

Before you begin, be sure to have the following in place:

• A Linux server with the relevant software installed
• Access to the command line interface
• Appropriate permissions (root or sudo)

Quick Fix

Wrong

ProxyPass /api http://localhost:3000\nProxyPassReverse /api http://localhost:3000

Wrong: Minimal proxy configuration

Right

ProxyPass /api http://backend:3000/\nProxyPassReverse /api http://backend:3000/\nProxyPassReverse /api http://backend.internal:3000/\nProxyPreserveHost On

Right: Proxy with PreserveHost and multiple reverse URLs

Output

Reverse proxy configured:\n  /api → http://backend:3000/\n  PreserveHost: On\n  Reverse URLs: 2 configured

Prevention

To avoid future issues, follow these best practices:

• Enable mod_proxy, mod_proxy_http with a2enmod
• Use ProxyPreserveHost On to send original Host header
• Add multiple ProxyPassReverse directives for different internal URLs
• Use ProxyTimeout to set backend timeout
• Use block for access control on proxied paths

DodaTech Tools

For further assistance with any of the above issues, consider using DodaTech consulting services or DodaTech tutorials for more in-depth guidance.

Common Mistakes with proxy pass

1. Forgetting deriving (Show, Eq) on custom data types needed for debugging
2. Placing the wildcard pattern first in case expressions, making all subsequent patterns unreachable
3. Using head and tail instead of pattern matching, causing runtime errors on empty lists

These mistakes appear frequently in real-world APACHE code. DodaTech's contributors have identified these patterns through analysis of open-source projects and production systems.

Practice Exercise

Write a pure function that safely divides two integers using Maybe, then test it with edge cases like division by zero and negative numbers.

This exercise reinforces the concepts covered in this guide. Try implementing it before checking online solutions.

FAQ