Azure Database for MySQl Flexible - High CPU - No increase in workload

Question

I have an Azure Web App that is connected to an Azure Database for MySQL Flexible server.

This web app is a small data collection form that stores the collected values to a table which are later collected via am API in the web app. A cron job executes once a day and deletes records that are older then 48 hours. On average the table contains 500 records at any one time.

All has worked very well for 18 months, the code deployment on the Web App has not changed since December 2022.

Since the 26th March the CPU usage of the Azure Database has reached and been stuck at 100% at various times until the instance is restarted. Error logs, slow query logs do not shed any light into the issue.

As you can see over then last 30 days, CPU is normally no higher than 30% until the 26th.

There has also not been an explosion of queries since the 26th.

The the time of writing CPU is at 46.6% - With no processes running on the MySQL server. (Backups are alse not running at this time)

From my perspective northing has changed. Is anyone else experiencing strange performance issues?

Answer 1

Hi @Jon Bromley ,

It seems that the issue is related to some Burstable B1s or B1ms MySQL flexible servers, where CPU usage is high. Using 1 vcore with MySQLFS consumed CPU Credit and CPU can be heavily utilized.

As per the product team, the recommendation is, for production workloads, transitioning to either the General Purpose or Business Critical tiers. Please review performance limitations of burstable series instances 
The Burstable tier is ideally more suited for non-production environments.
To specifically address CPU-related issues, advise transitioning from the B1s/B1ms size to the B2s or B2ms, or a higher SKU.

Thank You!