Azure Database for MySQL
An Azure managed MySQL database service for app development and deployment.
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100% CPU Usage in Azure Database for MySQL
Adrian
1
Reputation point
I have a sudden increase of CPU Usage in my Azure Database for MySQL Flexible Server with Standard B1ms Compute SKU. The CPU usage spikes in the middle of the night. There was no increase in queries.
No connection was possible to the Database Server when the CPU was on 100%, the issue was only resolved after I restarted the Server!
Has anyone else experienced such sudden CPU Usage increases and found a possible solution?
CPU Usage Monitoring:
As you can see here, there were no Slow Queries and a lot less Queries than before when the High CPU usage occured:
Azure Database for MySQL
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NIKHILA NETHIKUNTA 4,600 Reputation points Microsoft External Staff2025-02-07T12:47:07.06+00:00 @Adrian
Thank you for the question and for using Microsoft Q&A platform.Here are a few potential causes and solutions that might help:
- The Standard B1ms Compute SKU is a burstable instance, which means it uses CPU credits. When these credits are exhausted, the CPU performance can degrade significantly. For production workloads, it's recommended to transition to a General Purpose or Business Critical tier.
- Sometimes, background processes like maintenance tasks or backups can cause unexpected CPU spikes. Monitoring these processes might help identify if they are the cause.
- Even if the number of queries hasn't increased, a sudden surge in connections can lead to high CPU usage. Monitoring the "Total Connections" metric can help identify if this is the issue.
- Although you mentioned there were no slow queries, it's still worth checking if there are any inefficient queries running during the spike. Using the SHOW PROCESSLIST command can help identify any problematic queries. The SHOW (FULL) PROCESSLIST command displays a list of all user sessions currently connected to the Azure Database for MySQL Flexible Server instance. It also provides details about the current state and activity of each session.
- Monitoring other metrics like "Host Memory Percent" and "IO Percent" can provide insights into whether there are other resource bottlenecks contributing to the high CPU usage.
For more help, please refer to the below links:
https://learn.microsoft.com/en-us/azure/mysql/flexible-server/how-to-troubleshoot-low-memory-issues?source=recommendations
https://learn.microsoft.com/en-us/azure/mysql/flexible-server/concepts-service-tiers-storage#performance-limitations-of-burstable-series-instances
https://learn.microsoft.com/en-us/answers/questions/1663928/azure-database-for-mysql-flexible-server-unexpecte
https://learn.microsoft.com/en-us/azure/mysql/flexible-server/concept-monitoring-best-practices?source=recommendationsHope this helps. Please let us know if you have any further queries.
- The Standard B1ms Compute SKU is a burstable instance, which means it uses CPU credits. When these credits are exhausted, the CPU performance can degrade significantly. For production workloads, it's recommended to transition to a General Purpose or Business Critical tier.
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Adrian 1 Reputation point
2025-02-08T13:26:32.9533333+00:00 @NIKHILA NETHIKUNTA Thank you for your answer. I checked your suggestions and found the following:
- I checked the CPU Credits, they are exhausted AFTER the CPU rises to 100%, so the credits are not the cause of the issue.
- There was no Maintenance or Backup Task running at the current time.
- Total connections are not increased.
- I am unable to connect to the database to run commands when the CPU is on 100%. All incoming connections are failing! Is the process list logged somewhere to further investigate it after restart?
- Storage IO Percent is about 6-10%, so not reall high
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Adrian 1 Reputation point
2025-02-08T15:00:52.8833333+00:00 Today this issue occured on another Flexible Server Instance:
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NIKHILA NETHIKUNTA 4,600 Reputation points Microsoft External Staff
2025-02-10T12:42:38.6633333+00:00 @Adrian
Thank you for the details. Are you still facing the issue or is it resolved? -
NIKHILA NETHIKUNTA 4,600 Reputation points Microsoft External Staff
2025-02-12T07:53:16.41+00:00 @Adrian
We haven’t heard from you on the last response and was just checking back to see if you have a resolution yet. In case if you have any resolution please do share that same with the community as it can be helpful to others. Otherwise, will respond with more details and we will try to help. -
Adrian 1 Reputation point
2025-02-12T08:18:56.35+00:00 @NIKHILA NETHIKUNTA I have not resolved the issue so far. The high CPU Load stops after restart but I still don't know what is causing the issue.
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