ApsaraDB RDS:Configure the read and write attributes and the read weight of a database proxy endpoint

Prerequisites

Before you begin, make sure that you have:

• The database proxy feature enabled for your RDS instance. See Enable the database proxy feature

• At least one read-only instance attached to your RDS instance, required for read/write splitting. See Create a read-only ApsaraDB RDS for PostgreSQL instance

Read/write attributes

A proxy endpoint operates in one of two modes:

Behavior by attribute and weight

The following table describes how traffic is handled under each combination of read/write attribute and weight settings.

Notes on table terms:

• No traffic to primary: The primary instance is excluded from read-only request forwarding.

• Connection error: Occurs when a Read-only proxy endpoint has no available read-only instances to handle requests.

• Read/Write mode with primary weight = 0: Read requests are not forwarded to the primary instance under normal conditions. If all read-only instances are faulty, a forceful hint is specified, or transaction splitting is enabled, the proxy forwards read requests to the primary instance as a fallback.

Configure read/write attributes and read weight

1. Go to the Instances page. In the top navigation bar, select the region where your RDS instance resides, then click the instance ID.

2. In the left-side navigation pane, click Database Proxy.

3. In the Connection Information section, find the endpoint to modify in the Proxy Endpoint (Terminal) ID column, then click Modify Configuration in the Actions column.

4. Set Read/Write Attributes to one of the following:

   • Read/Write (Read/Write Splitting)

   • Read-only (Primary Instance Not Connected to Receive Write Requests)

5. Set Read Weight Allocation to Automatic or Custom:

   • Automatic: The system assigns a read weight to each instance based on its specifications. When you add a read-only instance, the system automatically includes it in read/write splitting with an appropriate weight — no manual update needed. For the weight values the system assigns, see Default read weights.

   • Custom: Specify a read weight for each read-only instance. Valid values: 0–10000. When you create a new read-only instance, its initial weight is 0 — update the weight to include it in traffic distribution.

   Note A higher weight means the instance receives proportionally more read requests. For example, if three read-only instances have weights 100, 200, and 200 and the primary instance weight is 0, the primary handles only writes and the read-only instances receive traffic in a 1:2:2 ratio.

   Weight changes take effect immediately with no connection drops. Existing connections are unaffected; only new connections use the updated weights.

Route requests with SQL hints

To override the proxy's routing decision for a specific query, add a routing hint to the SQL statement:

• Force the query to the primary instance:

  /*FORCE_MASTER*/ SELECT * FROM table_name;

• Force the query to a read-only instance:

  /*FORCE_SLAVE*/ SELECT * FROM table_name;

API reference