Overview

Although the cloud has certain high availability and automatic fault recovery capabilities, it still may cause short-time faults. An application system needs to handle such short-time faults, mainly by using the retry mechanism.

The following are typical scenarios where retries are required:

1. Connections may be interrupted during switchover of primary/standby instances, for example, DCS or RDS instances. In such a case, clients need to retry to restore connections.
2. If an instance is restarted due to a fault, the communication may be interrupted. For example, if the physical server where an ECS is located is faulty due to hardware reasons, the ECS is restarted or automatically restored on another physical server. During the restoration, the communication with the ECS is interrupted and a retry is required.
3. If an instance is overloaded, it cannot respond in a timely manner and a retry is required.