MariaDB instance in cloud hit 95% CPU utilisation for 30 mins

by Adam   Last Updated November 16, 2018 12:06 PM

I've got MariaDB instance in the cloud which I put live about 2 months ago. I'm new to the DBA business and I got the impression the people at the company who I run it through are learning on the hoof as well.

All is going well except that I saw CPU utilisation spiked on Tuesday to 95% for now apparent reason.

I requested performance stats after a user complained of a long running query. It turns out they were doing regular hourly queries on unindexed fields and the table scans involved suddenly took a lot longer. I am now looking at indexing this column so they can run their queries faster.

I'd like to know whether their queries could be the cause of the CPU utilisation, or whether whatever caused the CPU utilisation had just grabbed all the cache and caused their table scanning query to suddenly take far longer.

What should I be doing to capture information that will show what is going on and why the CPU utilisation spiked, and if it's a concern?

Here's the 5 days chart of CPU utilisation: enter image description here

and the 1 day chart enter image description here

and the only other chart that correlated with it:

enter image description here


enter image description here

The scales on the chart are probably the key, right?

The other charts provided (database connections, write IOPS, disk queue depth) didn't show any correlation.

I'm also puzzled why the normal pattern has totally changed.

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