Logback DBAppender sometimes gives error on AWS Aurora: IllegalStateException: DBAppender cannot function if the JDBC driver does not support getGeneratedKeys method *and* without a specific SQL dialect

LOGBack DBAppender IllegalStateException

Sometimes when starting a Spring Boot application with Logback DBAppender configured for PostgreSQL or AWS Aurora in logback-spring.xml, it gives this error:

java.lang.IllegalStateException: Logback configuration error detected: ERROR in ch.qos.logback.core.joran.spi.Interpreter@22:16 - RuntimeException in Action for tag [appender] java.lang.IllegalStateException: DBAppender cannot function if the JDBC driver does not support getGeneratedKeys method *and* without a specific SQL dialect

The error can be quite confusing. From the documentation it says that Logback should be able to detect the dialect from the driver class.

But apparently it doesn't. Sometimes. After investigating, it turns out that this error is also given when the driver can't connect correctly to the database. Because it will then not be able to find the metadata either, which it uses to detect the dialect. And thus you get this error too in that case!
A confusing error message indeed.

A suggestion in some post was to specify the <sqlDialect> tag, but that is not needed anymore in recent Logback versions. Indeed, it now gives these errors when putting it in logback-spring.xml file either below <password> or below <connectionSource>:

ERROR in ch.qos.logback.core.joran.spi.Interpreter@25:87 - no applicable action for [sqlDialect], current ElementPath  is [[configuration][appender][connectionSource][dataSource][sqlDialect]]
or
ERROR in ch.qos.logback.core.joran.spi.Interpreter@27:79 - no applicable action for [sqlDialect], current ElementPath  is [[configuration][appender][sqlDialect]]
To get a better error message it's better to implement the setup of the LogBack DBAppender in code, instead of in the logback-spring.xml. See for examples here and here.