Enabling http/2 in Apache 2.4 does not work

Question

We are trying to enable http/2 on Apache 2.4, but with no success. The server OS is FreeBSD 11.2, and the OpenSSL version is 1.0.2o.

We have a real and valid SSL Cer

Answer 1

Apache does not support HTTP/2 with prefork MPM. This was added in 2.4.27:

*) COMPATIBILITY: mod_http2: Disable and give warning when using Prefork. The server will continue to run, but HTTP/2 will no longer be negotiated. [Stefan Eissing]

The Prefork MPM is basically incompatible with the way HTTP/2 is implemented. There should be a warning in your error logs after restart telling you this.

Prefork is also a very old MPM that is slow, so those sites that want HTTP/2 probably shouldn't be using it anyway. It should only really be used if you are running non-threadsafe PHP applications (threadsafe ones should move to Event MPM and php-fm (which is basically how Nginx runs as it does not offer a prefork equivalent). Unfortunately it is also the default on many Apache installs (just i case people use thread-unsafe PHP applications?), and often you cannot change it without downloading and recompiling it.

More info on MPMs here: https://serverfault.com/questions/383526/how-do-i-select-which-apache-mpm-to-use