After Azure size upgrade Virtualmin painfully slow, Webmin fine

Upgraded the size of a server in Azure to F4 (from a B1) and now Virtualmin takes 20+ seconds to load pages related to the Virtualmin virtual servers. Webmin pages and actions all load less than a second. But try to load the list of the 11 virtual servers and it takes 60s. The server is not that busy and all of the virtual servers are perfectly responsive. A mix of web sites, APIs, and MySQL DBs. It’s as if something in Virtualmin got corrupted or lost it’s ability to have anything but the tiniest slice of CPU time.

Using Edge dev tools network tab looking at clicking the “List Virtual Servers” link:

Here’s the versions:
Operating system CentOS Linux 7.9.2009
Webmin version 1.973
Usermin version 1.823
Virtualmin version 6.16
Authentic theme version 19.73
Processor information Intel(R) Xeon(R) Platinum 8168 CPU @ 2.70GHz, 4 cores
CPU load averages 0.09 (1 min) 0.14 (5 mins) 0.14 (15 mins)
Real memory 4.41 GiB used / 2.34 GiB cached / 7.79 GiB total

It’s not the browser because I tried other browsers and get the same results. Also have other Azure servers running Virtualmin and not having issues there. Also verified same slowness with “Gray framed theme”.

I’ve looked everywhere for a setting that might have changed or something different on this server compared to other servers - and I come up dry. Not sure where else to look or how to further troubleshoot this issue. Is there a script to run to repair Virtualmin? Other ideas?

For starters, you could try re-running the configuration check from System Settings > Re-Check Configuration and see if everything passes or not.

You can also run top and then try to click the “List Virtual Servers” link or any other link to see if there is anything consuming excessive RAM/CPU when navigating in Virtualmin.

Rechecking the configuration indicates “your system is ready for use by Virtualmin.”

And oddly enough, “top” surfaces nothing; when “List virtual servers” (or any of the other virtual server related functions) is clicked, usr/libexec/we pops to the top of the list using about 2% CPU for about a second and then drops away. MySQL averages about 1-2% CPU steady and jumps to 70%+ with heavy web usage. But while the browser is grinding away for 60 seconds, nothing is eating up CPU or Memory.

Is there a Virtualmin site HTTP log file somewhere to search for this problem? The Edge browser tools shows that the time to first byte is a few ms and then just grinding for a long time afterwards.

The delay in loading the page was strange in that it didn’t trickle in, but a few bytes returned immediately and then a long grinding wait with nothing, followed by the entire page loading all at once. I began to suspect a timeout on something and DNS was the likely culprit.

Turns out when the Azure server was upgraded, the DNS name on Azure changed with a longer string stuffed in the middle and that pushed the HOSTNAME beyond 64 characters which caused it to be truncated. Everything on the server ran fine, but Virtualmin was stymied by this anytime you clicked through to a page that included info about a VM.

Fixed the hostname and now everything seems fine.

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