What is causing "stopped because of load"

[Gemini23]

Hosted with Siteground on own server (about 73% capacity) - recently I have been getting 503 errors when logged in and posting.
On checking today's cpanel logs - I see quite a few of these

[Fri May 25 22:07:42.310635 2018] [:error] [pid 27479] Execute of /home/xyzabc/public_html/index.php stopped because of load 36.61

Monthly Bandwidth Transfer29.59 GB / ∞
Disk Space 9.75 GB
MySQL Disk Space976.97 MB
Perl Version5.10.1
Kernel Version3.12.18-clouder0

Any suggestions?

[TorontoBoy]

There is capacity, on average for a month, but this does not consider load, and especially load spikes. You have a purchased certain amount of physical CPU memory. Go beyond this and you will cap out, your server might serve you 503s

From cPanel I have a "CPU and Concurrent Connection Usage", which goes to a page called "Resource Usage Overview". I click the "Details" link and get a bunch of graphs, one after another, by time. Look at the physical memory usage graph. If you hit 100% your server is at capacity and any other requests will get 503s, until the load subsides.

You might have overall average capacity, but there may be spikes that drive you over your physical memory usage. It might be a bot (good or bad), or something else, like your host provider running a maintenance job. I usually have a huge spike daily at 5:13am and I have no idea why, and my raw access log at that time shows no activity. I figured that the spike is server maintenance.

Find this graph, and correlate the spike timestamp to your raw access log. What do you see? Do you see huge activity? Who is it and what do they want? If you see no activity then talk to your host provider, as they may be running daily maintenance.

[Gemini23]

There are 3 cores in the CPU and today for example, only once did the 1 CORE get surpassed but nowhere near 2
which makes me questions why there is a CPU problem causing 503 errors..

[keyplyr]

If not already, I would employ heavy caching and compression.

[Frank1965]

Hi Gemini23, just a quick question: is this problem resolved and if so: what was causing it?

I'm asking because I have exactly the same problem, and also 3 cores at Siteground. And when I look at my CPU-usage, there are no spikes exceeding my 3 cores.

Siteground says I have to solve the problem myself, they don't know what's causing it...

Thanks a lot!
Frank

[justpassing]

load 36.61

It means that, the server would have required 37 cores to fulfill requests at this particular moment. If the traffic was "normal", I would look at disk access problems, and if this is network disks, then it says it all :)

I look at my CPU-usage

How do you check your CPU usage?

[Frank1965]

I don't know for sure if 36.61 means 36.61 cores.

When I look in my error log I see this recent one:
[Tue Oct 23 17:59:08.951682 2018] [:error] [pid 9488] Execute of /home/XYZ/public_html/index.php stopped because of load 31.95

But when I look at my CPU-usage in my Siteground panel, I don't see any spikes exceeding my 3 cores in the past days, and I have quite a lot of those errors in my error log.