Configuring auto scale-out
Last updated: 2025-10-27 19:10:23
This document introduces operations related to setting automatic scale-out.
Prerequisites
The instance architecture is TencentDB for MySQL general edition two-node, general edition three-node, and single-node local disk (read-only instance).
The instance specification is equal to or less than 32 cores before the CPU Elastic Scaling feature is enabled.
Your Tencent Cloud account has sufficient balance.
The underlying machine supports scale-out. If scale-out is not supported for the underlying machine, the operation of setting automatic scale-out will fail.
Billing Instructions
Enabling Automatic Scaling
Note：
After automatic scale-out is enabled, there is a very low probability that the feature will fail to be triggered. The backend will retry multiple times until the operation is successful.
1. Log in to the TencentDB for MySQL console. In the instance list, click an Instance ID or Manage in the Operations column to go to the instance details page.
2. On Instance Details > CPU Auto Scaling, click Enable.
3. In the Elastic CPU Expansion window, complete the following settings, and after confirming the scaling fee, click Expand Now.
Parameter | Description |
Scale-Out Method | Automatic expansion and custom scale-out are supported. Select automatic expansion here. Automatic expansion: Perform quick elastic scale-out according to performance to handle traffic peaks, and perform scale-in when traffic drops. Custom scale-out: You can select a period for scale-out and decide whether to enable automatic scale-out within other periods. |
Number of Cores for Scale-Out | The default value is consistent with the number of CPU cores of the current instance specification. For example, if the current instance specification is 6-core and 24,000 MB of memory, the number of cores for scale-out will also be 6 cores. After scale-out is successfully triggered, the CPU of the instance will be 12 cores. |
Increased IOPS | By default, the IOPS increases by 1000 for each core scaled out. |
Scale-Out Rule | Set the observation period and threshold for triggering scale-out. Observation period: Supported options include 15 seconds, 30 seconds, 45 seconds, 1 minute, 3 minutes, 5 minutes, 10 minutes, 15 minutes, and 30 minutes. Threshold: Supported options include 40%, 50%, 60%, 70%, 80%, and 90%. |
Scale-In Rule | Set the observation period and threshold for triggering scale-in. Observation period: Supported options include 5 minutes, 10 minutes, 15 minutes, and 30 minutes. Threshold: Supported options include 10%, 20%, and 30%. |
4. After automatic scale-out is triggered successfully, the interface will display as the following:
Modifying the Elastic Scale-out Policy for CPU
After automatic scale-out is enabled, only scaling rules can be modified under the feature. You may go to Instance Details > Elastic Scaling and click Modify for reconfiguration.
After automatic scale-out is enabled, it is not supported to directly change the scale-out method (from automatic scale-out to custom scale-out) through modification operation. If changes are needed, disable automatic scale-out first, and then adjust the method while re-enabling CPU elastic scale-out.
Disabling Automatic Scaling
Note：
After automatic scale-out is disabled, the CPU cores after scale-out will be immediately scaled in to the number before instance scale-out. After scale-in, scale-out will not be performed based on the scale-out threshold.
1. Log in to the TencentDB for MySQL console. In the instance list, click an instance ID or Manage in the operations column to go to the instance details page.
2. Navigate to Instance Details > Auto Scaling and then click Disable.
3. In the pop-up window End CPU Scaling, click OK.
FAQs
How to Determine If Auto-Scaling Is Effective After the Auto-Scaling Feature Is Enabled for CPU Elastic Scaling?
When the average CPU utilization of an instance reaches the set threshold for automatic elastic scale-out, the instance will be scaled out automatically. You can check whether the scale-out has taken effect by viewing the instance configuration on the instance details page. If the (actual number of cores) is also displayed after the number of CPU cores, it indicates that scale-out has taken effect. For example, if an instance is configured with 4 cores and 8,000 MB of memory, when the configuration displays as 4 cores and 8,000 MB, it indicates that automatic scale-out has not been triggered. When the configuration displays as 4 (8) cores and 8,000 MB, it indicates that the number has been scaled out to 8 cores.
Related APIs
API | Description |
This API is used to enable the CPU elastic scale-out feature for instances. | |
This API is used to disable the CPU elastic scale-out feature for instances. |
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