Intermittent radical slowing of J4 site

[jeffgilmore]

I run a J4 site which normally performs brilliantly fast--page load times of < 1 second typically.

This is hosted on a Liquid Web virtual server with 8 cores and 8 GB. I host a few development copies of the site on this same account/server/MariaDB server using different domain names.

The sites are all proxied and cached through Cloudflare, and I have pretty robust blocking of malicious bots and malware through the various facilities of Cloudflare's WAF (Web Application Firewall).

Intermittently, and for 20-30 minutes at a time, the system slows such that page loads are 30-90 seconds.

There are some obvious things I check during these events:
No noticeable spike in incoming traffic shown on Cloudflare
No noticeable spike in blockage of malware or bots on Cloudflare
Disabling Cloudflare cache doesn't fix it
Virtual server shows no spike in CPU, memory or IOwait times, and all are quite low
Other software running on the virtual server, like Cpanel and WHM operate at normal speeds
Nothing in the Apache logs look different
Accessing static assets from the server seem unaffected, even when I turn off Cloudflare cacheing. For example, I access a JPEG on the site using wget, and it loads in ~200ms:

Code: Select all

time wget --no-check-certificate --no-cache --no-cookies https://www.sample.org/images/test.jpeg --post-data="action=purge"

Most odd, the other development copies hosted on the exact same infrastructure operate at normal speeds

So given all that, what factors can you imagine could cause one Joomla site to go more slowly that an almost-identical site hosted in the same environment?

The only things that occur to me are:
Something with the database - while all these databases are on the same MariaDB instance, they are separate databases. Aside from corruption, which does not seem to occur, what can cause a database to crawl to a halt when others on the server do not?

Something Joomla code is doing - are there maintenance tasks or other events under the control of Joomla code that can have this kind of impact?

Something about a particular Apache Virtual Server instance - but they all are essentially identical, and all work great normally.

Anyone have any thoughts about what may be the culprit?

Are there tools within Joomla to help get a view into real-time performance?

Are there logs which might be useful to check (nothing useful ever seems to show up in the 'EVERYTHING.log file)?

[ceford]

You could turn on Debug mode and look at the Profile. It may tell you something.