[logback-user] Can I prevent logback's DBAppender from logging specific properties?

[Chris Pruett]

Logback's DBAppender logs all properties in its context and MDC to the
database. I would like to control which properties are logged,
specifically filtering out certain values, but I can't find any
options to do so. The documentation is terse:

> The logging_event_property is used to store the keys and values contained in the MDC or the Context

Is it possible to exclude certain properties from being logged?

Here is an example:

Logback is configured with a `DBAppender` that loads its properties
from `vct.properties`:

	<configuration>
		<property resource="vct.properties" />
		
		<appender name="DB" class="ch.qos.logback.classic.db.DBAppender">
			<connectionSource class="ch.qos.logback.core.db.DataSourceConnectionSource">
				<dataSource class="com.mchange.v2.c3p0.ComboPooledDataSource">
					<driverClass>com.mysql.jdbc.Driver</driverClass>
					<jdbcUrl>jdbc:mysql://${log.db.host}:${log.db.port}/${log.db.schema}</jdbcUrl>
					<user>${log.db.username}</user>
					<password>${log.db.password}</password>
				</dataSource>
			</connectionSource>
		</appender>
	
		<root level="DEBUG">
			<appender-ref ref="DB" />
		</root>
	</configuration>


`vct.properties` has the connection settings:

	log.db.host=localhost
	log.db.port=3306
	log.db.schema=logs_development
	log.db.username=loguser
	log.db.password=logpass

When an event is logged, all of the connection settings are logged:

	mysql> select * from logging_event_property where event_id=1;
	+----------+---------------------+-------------------------------------------+
	| event_id | mapped_key          | mapped_value                              |
	+----------+---------------------+-------------------------------------------+
	|        1 | log.db.host         | localhost                                 |
	|        1 | log.db.password     | logpass                                   |
	|        1 | log.db.port         | 3306                                      |
	|        1 | log.db.schema       | logs_development                          |
	|        1 | log.db.username     | loguser                                   |
	+----------+---------------------+-------------------------------------------+