This topic describes how to create an RDS for PostgreSQL read-only instance. You can create read-only instances to handle a large number of read requests and increase the application throughput. A read-only instance is a read-only copy of the master instance. Changes to the master instance are also automatically synchronized to all relevant read-only instances.

For more information, see Introduction to RDS for PostgreSQL read-only instances.

Prerequisites

  • The master instance is an RDS for PostgreSQL 10.0 High-Availability Edition instance.
  • The configuration of the master instance must be at least 8-core 32 GB (dedicated or dedicated-host instance).

Precautions

  • You can create read-only instances only from a master instance and cannot switch an existing instance to a read-only instance.
  • Creating a read-only instance does not affect the master instance because the read-only instance copies data from the corresponding slave instance.
  • Read-only instances do not inherit the parameter settings of the master instance, but use the default parameter settings. You can modify the parameter settings in the console.
  • The specifications and storage capacity of a read-only instance cannot be lower than those of the master instance.
  • Each master instance can have up to five read-only instances.
  • Read-only instances use the Pay-As-You-Go billing method. They are charged once every hour.

Create a read-only instance

  1. Log on to the RDS console.
  2. Select the target region.选择地域
  3. Find the target RDS instance and click the instance ID.
  4. Click Add Read-only instance.添加只读实例
  5. On the purchase page, select instance configurations and click Buy Now. 购买界面
    Note
    • We recommend that you deploy read-only instances in the same VPC as the master instance .
    • The configuration (specifications and storage capacity) of each read-only instance must be greater than or equal to those of the master instance.
    • You can deploy up to five read-only instances to improve availability.
  6. On the Order Confirmation page, select Terms of Service, Service Level Agreement, and Terms of Use, and click Pay Now to complete the payment.

The instance creation takes a few minutes.

View a read-only instance

To view a read-only instance in the instance list, follow these steps:
  1. Log on to the RDS console.
  2. Select the region where the read-only instance is located.
  3. Find the read-only instance and click the instance ID.

To view a read-only instance on the Basic Information page for the corresponding master instance, follow these steps:

  1. Log on to the RDS console.
  2. Select the target region.
  3. Find the master instance and click the instance ID.
  4. On the Basic Information page, move the pointer over the number of read-only instances and click the ID of the read-only instance.主实例内跳转只读实例

View the delay of a read-only instance

When a read-only instance synchronizes data from the master instance, the read-only instance may lag behind the master instance by a small amount of time. You can view the delay on the Basic Information page of the read-only instance.

只读实例延迟

APIs

API Description
CreateReadOnlyDBInstance Used to create an RDS read-only instance.