How are my connections handled when I reboot my Amazon for RDS instance with or without a failover?

Resolution

You might need to reboot your DB instance, usually for maintenance reasons. For example, if you make certain modifications or change the DB parameter group associated with the DB instance, then you must reboot the instance for the changes to take effect. Rebooting a DB instance restarts the database engine service. Rebooting results in a momentary outage of the instance, during which the instance status is set to rebooting. For more information, see Rebooting a DB instance.

When you reboot your Amazon RDS instance, you see the following events in the Logs & Events section on the Amazon RDS console:

Rebooting a Single-AZ Amazon RDS instance:
October 05, 2021, 4:31:22 AM UTC                          DB instance restarted

Reboot a Multi-AZ RDS instance without a failover:
October 18, 2021, 8:12:03 PM UTC                          DB instance restarted
October 18, 2021, 8:11:52 PM UTC                          DB instance shutdown

Rebooting a Multi-AZ RDS instance with a failover:
October 05, 2021, 2:15:33 PM UTC                          DB instance restarted
October 05, 2021, 2:15:18 PM UTC                          The user requested a failover of the DB instance
October 05, 2021, 2:15:18 PM UTC                          Multi-AZ instance failover completed
October 05, 2021, 2:13:18 PM UTC                          Multi-AZ instance failover started

Rebooting a Single-AZ Amazon RDS for Microsoft SQL Server instance:
October 05, 2021, 4:31:22 AM UTC                         DB instance restarted

Rebooting a Multi-AZ RDS for Microsoft SQL Server instance without a failover:
October 05, 2021, 4:32:22 AM UTC                         DB instance restarted
October 05, 2021, 4:32:20 AM UTC                         DB instance restarted

Rebooting a Multi-AZ RDS for Microsoft SQL Server instance with a failover:
October 05, 2021, 2:49:18 PM UTC                         Multi-AZ failover to standby complete - DNS propagation may take a few minutes
October 05, 2021, 2:49:11 PM UTC                         Multi-AZ instance failover completed
October 05, 2021, 2:48:42 PM UTC                         Multi-AZ instance failover started
October 05, 2021, 2:48:33 PM UTC                         DB instance restarted

When you reboot your DB instance either with or without a failover, the instance is shut down. Therefore, you must clean up and re-establish any existing connections to your DB instance. It's a best practice to implement database connection retry at the application layer. Rebooting with a failover is beneficial for simulating the failure of a DB instance for testing purposes or for restoring operations to the original Availability Zone after the failover.