Scaling Redis Instance Specifications Automatically

Notes and Constraints

• This function is available for DCS Redis 4.0 and later basic edition instances.
• Unavailable for instances with less than 4 GB memory.
• Available only for pay-per-use DCS instances.
• This function only supports automatic scaling to larger specifications. Cluster instances can only be scaled up.
• Automatic policies only apply in scale-out/up. To scale in/down an automatically-scaled instance, change the instance specifications by referring to Modifying DCS Instance Specifications.
• Performing instance specification changes (except for replica quantity changes) overrides the applied automatic scaling policies.

Impacts of Automatic Scaling

• During scaling, an instance is intermittently disconnected once or twice within 30 seconds, and becomes read-only within 1 minute.
• Auto scaling changes the configuration fee. Check your fee changes.

Configuring Automatic Scaling Policies

1. Log in to the DCS console.
2. Click in the upper left corner of the console and select the region where your instance is located.
3. In the navigation pane, choose Cache Manager.
4. Click the name of a DCS instance.
5. On the Basic Information page, click Auto Scaling after Cache Size.
   Figure 1 Automatic scaling
   

6. On the displayed Auto Scaling dialog box, click Add.
7. Set the policy name.

   4 to 64 characters. Start with a letter or digit and use only letters, digits, hyphens (-), underscores (_), and periods (.).

8. Automatic scaling can be triggered by conditions, or scheduled. Set as required.
   • Condition: The instance is automatically scaled out when the memory usage reaches the specified threshold. Set the condition by referring to Table 1.
   • Schedule: The instance will be automatically scaled and restored as scheduled. Set the schedule by referring to Table 2.

     Table 1 Condition parameters

     Parameter	Description
     Avg. Memory Usage ≥	Average memory usage threshold (%). For example, if this parameter is set to 70%, when the memory usage is greater than or equal to 70%, the instance is automatically scaled.
     Max. Specification	Maximum specifications (GB) can be scaled to. Use a value greater than the current. For example, if the instance uses 4 GB memory, and the max. specification is 32 GB, the instance memory will be automatically scaled to 8 GB as triggered, and then to 16 GB as triggered again. As a result, the maximum specification does not exceed 32 GB. Note: Automatically scaled instances triggered by condition cannot be done reversely. Change the instance specification as required by referring to Modifying DCS Instance Specifications.
     Monitoring Period	Monitoring time of the average memory usage, in minutes. The default value is 5. For example, if the monitoring period is set to 5 minutes, the average memory usage is calculated with 5-minute monitoring data.
     Silence	Interval between scaling operations, in seconds. The default value is 0. An automatically scaled instance will not be scaled again during the silence time if the average memory usage exceeds the threshold again. This mechanism prevents consecutive operations.

     Table 2 Schedule parameters

     Parameter	Description
     Operation	The target specification to be adjusted to.
     Effective	The instance specification will be adjusted within a schedule.
     Schedule	The instance specification will be scaled once, daily, weekly, or monthly.
     Start On	If Once or Daily is selected, specify the start time. If Weekly or Monthly is selected, weekdays or days of a month are also required. NOTE: Scheduled triggers work in GMT+8. If your instance is not in GMT+8, convert your timezone first.
     Restore On	If Once or Daily is selected, specify the restore time. If Weekly or Monthly is selected, weekdays or days of a month are also required. If the instance uses more than 70% of its original memory after scale-up/out, scale-in/down will not be automatically triggered.

9. Click Confirm.

   After a policy is submitted, to modify or delete it, click Edit or Delete on the right of the policy.

10. Click Apply after the policy to be executed. Confirm the operation and click OK. The policy will take effect, and be displayed under Applied Policies.

    To cancel a policy, click Cancel next to the policy and click OK. Applying a new policy replaces the old one. Multiple policies cannot be applied at the same time.

Viewing Auto Scaling Records

When automatic scaling is triggered, a specification change record by user auto-system can be viewed on the Background Tasks page on the console, as shown in Figure 2.

Figure 2 Auto scaling record