100% CPU on Empty MySQL Instance

Question

100% CPU on Empty MySQL Instance

Jason Bennett 15

Hello,

I recently setup an Azure mySQL Database. It is type Standard_B1s (small yes). I have not created any databases at all. The only thing in there is the default database mySQL comes with. There are no users, no-one connecting to it. Looking at the CPU metric, sometime yesterday the CPU hit 100% when I sleeping and has been lingering there for no apparent reason.

I checked "trx_rseg_history_len" and it came back 0. HLL = 0. There are no backups running and connected users is just me while troubleshooting and "azure_superuser" user

I can't figure out why the host CPU is 100% when I don't even have a database on it yet.

Any help appreciated.

Thanks

2 answers

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Answer 1

Oury Ba-MSFT 21,126 Microsoft Employee Moderator

@Jason Bennett

Thank you for reaching out.

I would suggest to first review your workload and considering using a different tier from Standard_B1s if you need stable performance all the time:

User's image

Azure Database for MySQL - Flexible Server service tiers

Regards,

Oury

Jason Bennett 15 Reputation points

2024-04-02T00:02:07.8766667+00:00

There is NO workload. NO user databases. Nothing to review.
Oury Ba-MSFT 21,126 Reputation points Microsoft Employee Moderator

2024-04-02T00:14:09.5666667+00:00

Jason Bennett

Seems like the above answer was not helpful. Please allow me sometimes to dig further into this issue and get back shortly.

Regards,

Oury
Oury Ba-MSFT 21,126 Reputation points Microsoft Employee Moderator

2024-04-02T15:36:56.6033333+00:00

Jason Bennett

Thank you for being patient while checking on this. Could you please create a support ticket so we can look further into this. Looks like this would need some troubleshooting.

Please let me know if yo don't have a support plan.

Regards,

Oury

Answer 2

RahulRandive 10,501 Volunteer Moderator

Hi @Jason Bennett

It's unusual to see a sudden spike in CPU usage on the Empty MySQL Flexible server. Please take a look at the document 'Troubleshoot high CPU utilization in Azure Database for MySQL - Flexible Server.'

https://learn.microsoft.com/en-us/azure/mysql/flexible-server/how-to-troubleshoot-high-cpu-utilization

It provides queries that can help you identify the current workload and any background processes that might be causing the issue.

Thank You!

Evangelos Markoulakis 0 Reputation points

2024-04-26T13:58:10.0166667+00:00

He says and i quote "There is NO workload. NO user databases. Nothing to review." The queries are not useful. Can you spend a minute to understand the issue? Read this too please before responding.
https://learn.microsoft.com/en-us/answers/questions/1651773/whats-going-on-with-the-flexible-mysql-database
RahulRandive 10,501 Reputation points Volunteer Moderator

2024-04-26T14:32:06.9266667+00:00

Hi @Jason Bennett,

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, we advise transitioning from the B1s/B1ms size to the B2s or B2ms, or a higher SKU. Thank You!
Phillip Parr 25 Reputation points

2024-05-25T15:37:31.5666667+00:00

@RahulRandive If you're suggesting that it's expected that a burstable server will randomly go to 100% CPU and sit there when there is no user data or traffic on it, then why offer the product? You can't sell something that knowingly doesn't work, and there's laws in many countries that will tell you that.
RahulRandive 10,501 Reputation points Volunteer Moderator

2024-05-25T20:11:47.13+00:00

Hi Phillip Parr,
Please feel free to open a support ticket to validate your server and determine the exact cause of the CPU spikes. The support experts can check the backend logs and provide you with the root cause of the increased CPU usage and can help in mitigating an issue.

Thank You!
Oury Ba-MSFT 21,126 Reputation points Microsoft Employee Moderator

2024-05-28T22:43:58.9666667+00:00

Phillip Parr

As suggested by @RahulRandive

Were you able to open a support ticket.?

Regards,

Oury
Phillip Parr 25 Reputation points

2024-05-28T22:56:27.17+00:00

@Oury Ba-MSFT Just waiting for my internal team to let me know who my internal MS contacts are, then I absolutely will 😊
Oury Ba-MSFT 21,126 Reputation points Microsoft Employee Moderator

2024-06-05T21:38:12.0166667+00:00

Phillip Parr

Sounds good. Thank you
Phillip Parr 25 Reputation points

2024-06-10T14:40:16.8566667+00:00

Ok so after having a Teams meeting with your support guys the answer is: You don't support the minimum tier, you won't look into why it's unstable, and your only advice is to upgrade to a General Purpose vs Burstable tier.

Given the price of the General Purpose tier, Azure is not a product I'd ever recommend to a small business. But, since I work for a corporation, I decided to test out another burstable compute size.

I moved from B1s 1 vCore 1GiB ($8.07/m) to B2s 2v Cores 4GiB ($48.84/m) and saw an immediate resolution to the issues. No longer was the CPU all over the place when under no load, but instead it is a fairly solid 2 - 3% when idle, except for a process that seems to be running for 1 hour every 8 hours which consumes 10%; no idea what this is, presumably it's an Azure process as it's not me.

Based on the simple difference of these two levels, I believe that your B1s offering for MySQL flexible server is fundamentally broken at this time, and it is frustrating that you will not look to resolve it.

Here's some graphs showing the minimum and maximum CPU usage, and the inserts / selects on the database. See if you can work out when I upgraded.

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100% CPU on Empty MySQL Instance

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