ApsaraDB RDS:What are database proxies?

Overview

A database proxy serves as a network proxy that resides between your database system and your application and receives all requests from your application. You can connect to your RDS instance by using a database proxy endpoint to use various capabilities of the database proxy feature. This simplifies the connection management of the RDS instance. For more information, see Use a database proxy endpoint to connect to an ApsaraDB RDS for PostgreSQL instance.

Scenarios

• The primary RDS instance is heavily loaded due to a large number of requests that are encapsulated in transactions.

• The primary RDS instance is heavily loaded due to an excessively large number of connections.

• Read/write splitting is required.

• You need to process read-only workloads and isolate workloads.

  Note

  Assume that your database system consists of one primary RDS instance and four read-only RDS instances, and you have two applications, Application A and Application B. Application A initiates only read requests, and Application B initiates both read and write requests. You want to connect Application A and Application B to the database system. You can bind two read-only RDS instances to Proxy Terminal A that has the Read-only attribute to process the requests from Application A and bind the primary RDS instance and the other two read-only RDS instances to Proxy Terminal B that has the Read/Write attribute to process the requests from Application B. This way, Application A and Application B are physically isolated from each other in your database system.

Terms

• database proxy endpoint (formerly known as proxy terminal)

  Database proxy endpoints are the core of database proxies. You can configure connection settings for a database proxy endpoint based on your business requirements, the prefix of the database proxy endpoint, and the port that is associated with the database proxy endpoint. If you use a database proxy endpoint to connect to an RDS instance, you can use the advanced capabilities of the database proxy feature.

  Each RDS instance with the database proxy feature enabled supports up to seven database proxy endpoints. You can apply for one internal endpoint and one public endpoint for each database proxy endpoint. You can also configure connection settings for each database proxy endpoint to meet different business requirements and improve service flexibility. For more information, see Configure the connection settings for a database proxy endpoint and Use a database proxy endpoint to connect to an ApsaraDB RDS for PostgreSQL instance.

• read/write splitting

  Read/write splitting indicates that database proxy endpoints can be used to automatically forward read and write requests.

  If your database system receives a large number of read requests and a small number of write requests, the primary RDS instance may fail to efficiently process read requests and your workloads may be interrupted. The read/write splitting feature allows the system to forward write requests to the primary RDS instance and read requests to the read-only RDS instances. This reduces the loads on the primary RDS instance. For more information, see What is read/write splitting?

• transaction splitting

  The transaction splitting feature is automatically enabled for a database proxy. This feature allows the system to forward the read requests prior to write operations in a transaction to the read-only RDS instances of your database system. This reduces the loads on the primary RDS instance. For more information, see Transaction splitting.

  Note

  • Explicit transactions cannot be split. These explicit transactions include the transactions that are started by executing the BEGIN or START statement.

  • If the transaction splitting feature is enabled, global consistency cannot be ensured. Before you use this feature, we recommend that you evaluate whether this feature is suitable for your workloads.

  • The transaction splitting feature cannot be disabled.

Types of database proxies

ApsaraDB RDS for PostgreSQL provides general-purpose and dedicated database proxies.

• General-purpose: Database proxies share physical CPU resources and are provided free of charge. This type of database proxy is cost-effective.

• Dedicated: Database proxies exclusively occupy the allocated physical CPU resources and are charged based on the pay-as-you-go billing method. This type of database proxy delivers stable performance.

The following table describes the differences between the two types of database proxies.

Usage notes

For more information, see Usage notes of database proxies.

Billing rules

For more information, see Billing rules for database proxies.

Usage

For more information, see Use the database proxy feature.