Haproxy 3.0 with PHP-FPM: Unraveling the Mystery of the Mangled 301 Header

Are you tired of seeing your carefully crafted 301 redirects transformed into 302s by Haproxy and PHP-FPM? You’re not alone! In this article, we’ll delve into the intricacies of this issue and provide you with a step-by-step guide to resolving it once and for all.

The Problem: 301 Header Mangled to 302

When using Haproxy 3.0 as a load balancer in front of PHP-FPM, you might notice that your 301 redirects are being mangled into 302s. This can lead to issues with SEO, as search engines treat 301 and 302 redirects differently. But what’s causing this behavior, and more importantly, how can you fix it?

The Culprit: PHP-FPM and Haproxy’s Complex Interplay

The root of this problem lies in the complex interplay between PHP-FPM and Haproxy. By default, PHP-FPM uses a buffering mechanism to improve performance. However, this buffering can sometimes lead to the HTTP headers being rewritten, resulting in the 301 redirect being transformed into a 302.

Meanwhile, Haproxy, being the diligent load balancer it is, diligently follows the HTTP spec and honors the headers provided by PHP-FPM. Little does it know, these headers have been tampered with, causing the 301 redirect to be mangled into a 302.

Solving the Mystery: Configuration Tweaks and Workarounds

Now that we’ve identified the culprits, it’s time to put on our detective hats and get to work on solving this mystery. Here are some configuration tweaks and workarounds to help you untangle the mess:

1. Disable PHP-FPM Buffering

One of the simplest solutions is to disable PHP-FPM’s buffering mechanism. This can be done by adding the following lines to your PHP-FPM configuration file:

[www]
pm.max_children = 50
pm.start_servers = 20
pm.min_spare_servers = 20
pm.max_spare_servers = 30
php_admin_value[output_buffering] = Off
php_admin_flags[output_buffering] = Off

By disabling output buffering, you ensure that PHP-FPM doesn’t tamper with the HTTP headers, allowing Haproxy to receive the correct 301 redirect.

2. Use Haproxy’s “httpchk” Option

Haproxy’s “httpchk” option allows you to specify a custom HTTP request to be sent to the backend server during health checks. By leveraging this option, you can instruct Haproxy to ignore the buffers sent by PHP-FPM:

frontend http
    mode http
    bind *:80

    httpchk GET /healthcheck
    server web1 127.0.0.1:80 check interp 200,302,301,404

In this example, Haproxy sends a GET request to the “/healthcheck” URL during health checks, effectively ignoring any buffers sent by PHP-FPM.

3. Utilize Haproxy’s “reopen” Option

Haproxy’s “reopen” option allows you to specify a custom HTTP header to be sent with each request. By using this option, you can override the mangled 301 header with the correct one:

frontend http
    mode http
    bind *:80

    http-response set-header Location %[resp.hdr_Location],%[req.uri] if { req.uri ~ /my-old-url }
    reopen wait
    server web1 127.0.0.1:80

In this example, Haproxy sets the “Location” header to the correct value, overriding the mangled 301 header sent by PHP-FPM.

4. Employ a Custom Solution with Haproxy’s “lua” Module

For more complex scenarios, you can utilize Haproxy’s “lua” module to write custom logic for handling the mangled 301 header. Here’s an example:

http-response lua.replace_header("Location", %[req.uri], "/my-old-url") if { req.uri ~ /my-old-url }

This Lua script replaces the mangled 301 header with the correct one, allowing you to maintain control over the redirect process.

Conclusion: Regaining Control Over Your Redirects

With these configuration tweaks and workarounds, you should now be able to untangle the mess caused by PHP-FPM’s buffering mechanism and Haproxy’s diligent adherence to the HTTP spec. By regaining control over your redirects, you can ensure that your website’s SEO remains intact, and your users are redirected to the correct locations.

Additional Tips and Tricks

• Make sure to test your configurations thoroughly to ensure that they don’t introduce any new issues.
• Consider implementing a caching layer, such as Varnish, to reduce the load on your PHP-FPM and Haproxy instances.
• If you’re using a Content Delivery Network (CDN), ensure that it’s properly configured to handle the redirects correctly.

Final Thoughts: The Importance of Attention to Detail

In the world of web development, attention to detail is crucial. What may seem like a minor issue can have far-reaching consequences, as we’ve seen with the mangled 301 header. By being aware of the intricacies of PHP-FPM and Haproxy’s interactions, you can ensure that your website’s redirects are handled correctly, and your users are redirected to the correct locations.

Remember, in the words of the great detective Sherlock Holmes, “The world is full of obvious things which nobody by any chance ever observes.” Today, we’ve observed the obvious and taken control of our redirects. Tomorrow, who knows what other mysteries we’ll unravel?

PHP-FPM Configuration	Haproxy Configuration
Disable buffering	Use “httpchk” option
	Utilize “reopen” option
	Employ custom solution with “lua” module

By following these guidelines and keeping a keen eye on the intricacies of your setup, you’ll be well on your way to resolving the mystery of the mangled 301 header and ensuring that your website’s SEO remains intact.

Frequently Asked Question

Haproxy 3.0 with PHP-FPM 301 headers got you puzzled? Don’t worry, we’ve got you covered! Check out these FAQs to troubleshoot the issue and get your 301 redirects working smoothly.