If you see the following connection errors, this applies to your case.
MariaDB Error Log
[Warning] Aborted connection 46019374 to db: 'unconnected' user: 'unauthenticated' host: 'xx.xxx.xx.xx' (This connection closed normally without authentication)
PostgreSQL Log
[unknown]@[unknown]:[20437]:LOG: incomplete startup packet
Cause and Resolution
The Private IP of Cloud Z DB in the AWS environment uses AWS Network Load Balancer (NLB).
The AWS NLB (Network Load Balancer) service performs its own health checks using TCP ping.
Due to this, connection errors are recorded in the DB, but these are harmless and can be ignored.
In the case of MariaDB, you can prevent this error from being logged by configuring the parameter log_warning=1.
(Reference : https://mariadb.com/kb/en/error-log/#configuring-the-error-log-verbosity )
Procedure to configure log_warning=1 parameter
1. Edit Configuration
Go to the Configuration tab in the ZDB Console, select the desired Target, and add the line log_warning=1.
Click the 'Update' button at the bottom right to save the changes.
(If you want to apply this to both Primary and Secondary, you must set the Target individually for each.)
2. Apply the updated Configuration
A service restart is required to apply the updated Configuration.
If you wish to apply it without restarting the service, connect to the DB and execute the following command:
(Run this separately for Primary and Secondary)
SET GLOBAL log_warnings=1;
In this case, the Console may detect that the updated Configuration has not been applied and trigger a 'Configuration not apply' event.
(This event will no longer occur once the service is restarted, so it can be ignored.)