Changing Read Weights of Nodes

After a proxy instance is created, you can change the read weights of its associated nodes. Read requests are forwarded to each node based on the read weights you specify, enabling read/write splitting and reducing the load of the primary node.

Constraints

This function is only available for proxy instances that use the weighted routing policy.
You can configure read weights for both the primary node and read replicas.
The default read weight of the primary node is 0. The higher read weight the primary node is assigned, the more read requests it can process.
When the read weights of all nodes are 0, services are not affected. In this case, the primary node processes all read and write requests by default.
The weight of a read replica ranges from 0 to 1000.

After Associate New Nodes is enabled, new read replicas will be automatically associated with the current proxy instance. The default read weight of any new node is 100.
After a read replica is deleted, its weight is automatically removed while the weights of other read replicas remain unchanged.

Procedure

Log in to the management console.
Click in the upper left corner and select a region and project.
Click in the upper left corner of the page and choose Databases > TaurusDB.
On the Instances page, click the instance name to go to the Basic Information page.
In the navigation pane, choose Database Proxy. Then click the name of a proxy instance.
On the Basic Information page, click Configure under Routing Policy.
In the displayed dialog box, select the nodes that you want to associate with the current proxy instance or deselect the nodes that you want to remove from the current proxy instance in the Database Nodes area, and configure read weights in the Read Weight column.

Figure 1 Configuring read weights

Example:

As shown in Figure 2, one TaurusDB instance has one primary node and three read replicas. Two proxy instances have been created and they both use the weighted routing policy.
- Proxy instance 1 is in the read/write mode. The primary node and read replica 1 are associated with proxy instance 1 and assigned with a read weight of 100 and 200, respectively. They process read requests in the ratio of 1:2, that is, the primary node processes 1/3 read requests and read replica 1 processes 2/3 read requests. Write requests are automatically routed to the primary node.
- Proxy instance 2 is in the read-only mode. Read replica 2 and read replica 3 are associated with proxy instance 2 and assigned with a read weight of 100 and 200, respectively. Read replica 2 and read replica 3 process read requests in the ratio of 1:2, that is, read replica 2 processes 1/3 read requests, and read replica 3 processes 2/3 read requests.
Figure 2 Read/Write splitting in multi-proxy scenarios (weighted routing policy)
Click OK. The proxy instance status changes to Configure routing policy.
After several minutes, check that the proxy instance status becomes Available and the read weights are updated.