Adding Read Replicas to a Standard HTAP Instance

Scenarios

In read-intensive scenarios, the primary instance may be unable to handle the read pressure and services may be affected. To offload read pressure from the primary node, you can create one or more read replicas. These read replicas can process a large number of read requests and increase application throughput.

After creating a standard HTAP instance, you can add read replicas to it as required.

Deployment Relationships

New read replicas and existing nodes are deployed in the same AZ.

Constraints

• A single cluster instance supports a maximum of 10 FE nodes and 10 BE nodes.
• You cannot add read replicas to a single-node instance.
• Deleted read replicas cannot be recovered. Exercise caution when performing this operation.
• If another operation is being performed on a DB instance, the read replicas of the instance cannot be manually deleted.
• In a single cluster instance, you can only delete a fe-follower node when there is one fe-leader node and two or more available fe-follower nodes.

  For details about the fe-leader and fe-follower nodes, see What Is HTAP Standard Edition?

• Read replicas of a single-node instance cannot be deleted.
• If a standard HTAP instance has been associated with a proxy instance, you need to manually configure read weights for new read replicas.

Billing

Procedure

1. Log in to the management console.
2. Click in the upper left corner and select a region and project.
3. Click in the upper left corner of the page and choose Databases > TaurusDB.
4. On the Instances page, locate a TaurusDB instance and click its name to access the Basic Information page.
5. In the navigation pane, choose HTAP Analysis.
6. Locate an HTAP instance and choose More > Create Read Replica in the Operation column.
7. On the displayed page, set required parameters.
   Figure 1 Creating read replicas
   

   Table 2 Parameter description

   Parameter	Description
   Instance node flavor configuration	Storage Type: By default, the value is the same as that of the current HTAP instance and cannot be changed. Instance Specifications: By default, the value is the same as that of the current HTAP instance and cannot be changed.
   FE node configuration	Frontend Node Specifications: By default, the value is the same as that of the current HTAP instance and cannot be changed. Frontend Node Storage: By default, the value is the same as that of the current HTAP instance and cannot be changed. Frontend Node Role: By default, the value is the same as that of the current HTAP instance and cannot be changed. Frontend Nodes: The value ranges from 0 to 7. You can create up to 7 nodes at once.
   BE node configuration	Backend Node Specifications: By default, the value is the same as that of the current HTAP instance and cannot be changed. Backend Node Storage: By default, the value is the same as that of the current HTAP instance and cannot be changed. Backend Nodes: The value ranges from 0 to 7. You can create up to 7 nodes at once.

8. Click Next.
9. Confirm the information and click Submit.
10. After the read replicas are created, view and manage them on the Basic Information page of the HTAP instance.
    • Pay-per-use instance: To delete a read replica, locate the read replica in the node list and click Delete in the Operation column. In the displayed dialog box, click OK.
    • Yearly/Monthly instance: To delete a read replica, locate the read replica in the node list and click Unsubscribe in the Operation column. On the displayed page, confirm the order to be unsubscribed and select a reason. Then, click Confirm. In the displayed dialog box, click Yes. After the order is successfully unsubscribed, the read replica will be deleted.