Suddenly delay of 5 seconds on issue/article views


We’re running an OJS instance for a while now, but on 2023-03-02, problems appeared with “issue views” and “article views” - all pages take more than five seconds to load. This problem did not appear before that - every morning, we’re running some connections tests to see if everything is okay. You can see the results of the tests here: Archive Page (everything normal), “Current Issue” and values for a single journal. The base url is, if you’d like to check for yourself. It affects all journals. Seeing that there’s a sudden increase of about 5 seconds, it feels like there’s a sleep(5) somewhere (no request took less than 5 seconds), it’s strangely consistent in that way. It only affects our live server, the development server is unaffected.

We’re running the setup in docker, one container for OJS, one for the database. There were no problems before. There was no change in hardware, and the last software change was on 2023-01-15, to add a verification page for the Google crawler.

OJS: (14 July 2021 - 09:19)
OS-Plattform Linux
PHP-Version 7.3.22
Apache-Version Apache/2.4.48 (Unix)
Datenbanktreiber mysql
Version des Datenbankservers 5.5.5-10.2.37-MariaDB-1:10.2.37+maria~bionic

I don’t really know how to fix this - no changes were made, and no log displays unusual behaviour. The hardware is not under stress. Does anyone have an idea how to fix this?