Extremely slow server, almost halting all requests (load average 5)

Posted October 31, 2019 4.6k views
NginxPHPServer OptimizationWordPressLEMPUbuntu 18.04

I have noticed that occasionally, my web server becomes extremely slow. It becomes so slow, it’s almost impossible to load a page (takes more than 30 seconds, if it doesn’t timeout).

Running sudo service nginx restart does not solve the problem. Only thing that solves the issue is running sudo reboot. It works, but after some time (sometime days, sometime hours, sometimes minutes) it will become very slow again.

We’re running WordPress with WooCommerce. It doesn’t seem to have anything to do with traffic.

When I go into htop I notice extreme load average (last time it was 4, today it was 5!).

Here’s a screenshot of my htop:

I notice that even during slowness of the server, ssh seems to work quite fast despite.

At the moment, the issue seem to recur quite fast after a reboot, which is very critical since this is our production environment. I have made no changes to server, since for instance yesterday, where it was running just fine.

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1 answer

Hi @mattiasf,

It sounds like, a lot of processes are being created and not being stopped. Additionally, it’s possible you have a lot of mount points being created as well.

From the htop image you provided, indeed everyhing seems alright however, when the issue occur, please try check the following

netstat -punta

It will show you every connection to your droplet. There might be a lot of SYN requests not closing up. If there are a lot of requests, check the IP addresses, it’s possible someone has actually targeted your Droplet, it’s possible.

Another solution might be to try and do the following

systemctl daemon-reexec

This should give systemd a nice kick to get things working.