CPU and Server Memory Spikes

One day, around the end of March, our site (onlinesupport.co.uk) was returning memory or server errors to users trying to access the site.

Checked the cPanel, and disk space was full – it hadn’t been anywhere near full before.

Removed some archive pages from the Wordfence cache and that seemed to do the trick – everything back to normal in terms of disk space. Around this time we also made some minor changes to the php files in the header – we use a blank theme and the site was designed/hard coded by a developer, so when we make changes to the code, we have to be very careful we make sure we know what we’re doing. The changes were made and had the desired affect.

Soon after this, though, CPU, vMem and pMem usage started spiking to 100% very often, every hour for 15 minutes or so – wasn’t always denying access to the site but was at the very least slowing it down.

We checked and saw we were being hammered by a Russian IP address on xml.rpc and wp-cron so blacklisted IP addresses that may have been attempting to DDoS the site. Didn’t really make a difference.

We have looked at which plugins might have been causing the issue by using a process of elimination, but nothing in particular seems to be causing the spikes. Some plugins have been using more resources than others, but nothing over the top.

For about a week during June, the spikes were constant and severe – this caused us to drop like a stone in the google rankings – this is where it became a major, major problem.

We’ve upgraded to a managed service on our shared hosting plan and disabled wordfence (we use it for caching). We also removed Jetpack from the site. It’s not spike as much as it did for that week in June, but it is certainly not back to normal. We have another site hosted by the same company (on a different server), and whilst that maxes out, the average usage remains a constant around 0%, whereas on the site that has had the connectivity problems, the average usage is spiking all the time.

Does anyone have any idea what may be causing the issue? An open tag in the php files?

The hosting company say that every other site on the server we are on has no problems.

Thanks in advance for any help ??

https://postimg.org/image/w1ngl27gn/
Link with the resource usage graphs from the last 30 days – you can see the week it was really bad and how it’s been since.

moderator note: please do not ‘bump’ your topic as that is not permitted here and it removes the topic from the ‘no replies list’