During the night of April 1st to 2nd, something changed in the environment of my site, making it inaccessible:
Error 503 Backend fetch failed Backend fetch failed Guru Meditation: XID: ... Varnish cache server
I didn't make any changes, and my WordPress plugins were not updated at that time. With the current level of analysis, I get the impression that all accesses to resources usually accessed via an external URL (but to my domain) no longer work. For example, I had in some of my pages shortcodes with the Code Embed extension pointing to https://monsite.com/monchemin/moncode.php}, or the wpDataTables extension pointing to https://monsite.com/monchemin/monfichier.json.
I understand that “Code Embed” no longer exists and poses risks, so I'm changing strategy, but for wpDataTables, a strategy change doesn't seem feasible, and I would at least like to be able to edit the links in the admin interface, but I get the 503 error...
Do you know if a server configuration update has been made to block the use of URLs? (and without a whitelist pointing to the current domain?) I've read, for example, about allow_url_include where we don't have control.
I changed the IP in both places. Now the pages load, and visibly without error (content as expected and no error in the logs if I looked closely).
I understand that the "manip" was meant for debugging, but the bug visibly disappears, so could the CDN be at the root of the problem, with some rule change possibly blocking external URLs (if this hypothesis is correct)?
In any case, thanks because at least I can now access the wpDataTables admin page and try replacing the URLs with paths for supposedly better compatibility, and I’ll see later whether I put the CDN back.