I have apache 2.4.41 on Ubuntu 20.04 and run a certain application through PHP-FPM, with the MPM set to 'event'. Recently, in an attempt to speed up the application, I enabled HTTP/2 in the virtualhost by adding Protocols h2 http/1.1. Of course I first checked if the HTTP2 module was enabled using apachectl -M. I checked the response from the server: HTTP/2 is working. Apache2 accepts the protocol handshake and the application is noticeably faster.
Now after a few days (or sometimes hours) of use, the application stops responding to requests. When I check htop, I don't see high CPU processes or memory usage. Checking the status of apache, php-fpm and mariadb processes doesn't reveal any error either.
I removed the h2 parameter from the Protocols directive and reloaded apache, which solves it. But of course I would like to use HTTP/2. Does anyone have any idea what could be causing this? Which logs I could check to get a clue, or which tests I could perform?
