Starting August 1, 2024, ApsaraDB RDS for MySQL instances running database proxy version 2.9.1 support persistent connections during a failover. This reduces connection interruptions and improves connection reliability.
Background
When a primary RDS instance fails, the system automatically promotes a secondary instance as the new primary and switches workloads over. Because this switchover is unplanned, it is called a failover — and it typically interrupts active client connections.
How it works
The database proxy caches SQL statements that are being executed or queued for forwarding. When an RDS instance fails, the backend connections between the database proxy and databases on the RDS instance are interrupted. When the proxy detects a failover, it does not immediately drop client connections. Instead, it forwards failed read requests to an available RDS instance and restores the connection automatically. For details, see Configure persistent connection settings.
Limitations
Write requests are not guaranteed. The database proxy cannot ensure that write requests succeed during a failover, so connections handling write requests are interrupted.
Proxy type matters. General-purpose database proxies support persistent connections only during planned switchovers. Dedicated database proxies support persistent connections during both switchovers and failovers.
Billing
Persistent connections are free. For details, see Billing rules for database proxies.
Prerequisites
Before you begin, ensure that you have:
An RDS instance running MySQL 5.6, MySQL 5.7, or MySQL 8.0
An RDS instance running RDS High-availability Edition or RDS Cluster Edition
An RDS instance using cloud disks or local disks
An RDS instance using dedicated database proxies
The database proxy feature enabled and the database proxy version set to 2.9.1. For details, see Enable the database proxy feature
If Persistent Connections does not appear in the console, the instance does not meet the prerequisites above.
Enable or disable persistent connections
Log on to the ApsaraDB RDS console. In the top navigation bar, select the region where your RDS instance resides, find the instance, and click the instance ID.
In the left-side navigation pane, click Database Proxy.
In the Basic Information section, click Enabled to the right of Persistent Connections to enable the feature, or click Disabled to disable it.
If you do not find Persistent Connections, your RDS instance does not meet the prerequisites.