Enabling HTTP/2 in Apache on Ubuntu 18.04

A number of requirements must be met before HTTP/2 can be enabled for a website. This is a compilation of steps I went through to get HTTP/2 working on our Apache web server hosting WordPress sites.

HTTP/2 Requirements

Requirement #1: HTTPS

HTTP/2 only works with HTTPS. If you have not switched your site to HTTPS, now is the time to do it. You might be interested in my article Switching a WordPress Site From HTTP to HTTPS.

Requirement #2: Apache 2.4.24

The first version of Apache to support HTTP/2 is 2.4.24. If you are on the LTS branch of Ubuntu, this means you need to upgrade to Ubuntu 18.04. I described the upgrade process from 16.04 to 18.04 in another blog post.

Requirement #3: PHP FPM

Short version: if you run PHP in Apache via mod_php, you need to switch to FPM. That is not a bad thing. FPM is newer and faster.

Long version: HTTP/2 is not compatible with Apache’s prefork multi-processing module. However, prefork basically seems to be obsolete so it does not hurt to switch to something more modern, i.e., the event MPM. That, in turn, requires a change in the PHP module from mod_php to php7.x-fpm.

Configuration Changes for HTTP/2

Switching Apache’s PHP Module from MPM Prefork to Event

Run the following commands:

sudo apt-get install php7.2-fpm
sudo a2enmod proxy_fcgi
sudo a2enconf php7.2-fpm
sudo a2dismod php7.2
sudo a2dismod mpm_prefork
sudo a2enmod mpm_event
sudo service apache2 restart
Caveat: W3 Total Cache Shows Apache Modules as Not Detected

W3 Total Cache seems to rely on the function apache_get_modules() to detect Apache modules, which does not work with FPM. According to this support article from Plesk, this issue can be ignored.

Installing and Enabling HTTP/2 in Apache

Enable the module mod_http2:

sudo a2enmod http2
sudo service apache2 restart

Enable the HTTP/2 protocol by adding the following to /etc/apache2/apache2.conf:

Protocols h2 http/1.1

How to Verify that HTTP/2 is Working

Cloudflare put together a comprehensive list of ways you can check a website for HTTP/2 support. The easiest to use are probably Chrome Dev Tools (network view, add the Protocol column) or the online test from KeyCDN.

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3 Responses to Enabling HTTP/2 in Apache on Ubuntu 18.04

  1. Sebastian January 20, 2019 at 03:25 #

    Thank you! It works like a charm

  2. Carlo January 26, 2019 at 03:42 #

    Works perfect, Thank you

  3. Josh Espinoza January 30, 2019 at 17:04 #

    Hi,

    I used this article to switch our Ubuntu 18.04 Web server to HTTP2.

    We ran into a major issue though. if any page was saved with a problem. For example, a client saved a single image on a page that had spaces in the file name. it completely crippled Apache for about 15 minutes. the server didn’t show any signs of issues otherwise. The only error in the error log “server reached pm.max_children setting (5), consider raising it”. Any ideas on how to fix this? I want to use HTTP2 but we had to revert back to the prefork for stability

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