Provide built-in utility appender that silently stores last few logging messages and dumps them (forwards to a target appender) only when an error occurs. Older logging events are replaced with new ones. This is a configuration example:

<configuration>
<appender name="REC" class="ch.qos.logback.classic.RecordingAppender">
<appender-ref ref="STDOUT"/>

<maxEvents>1000</maxEvents>
<dumpThreshold>WARN</dumpThreshold>
<expiryTimeMs>15000</expiryTimeMs>
</appender>

<appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
<encoder>
<pattern>%-4relative [%thread] %-5level - %msg%n</pattern>
</encoder>
</appender>

<root level="DEBUG">
<appender-ref ref="REC"/>
</root>
</configuration>

Such an appender is crafted manually by several users, it would be nice to provide it out of the box. I already implemented this feature (100% test coverage):

https://github.com/nurkiewicz/logback/tree/recording-appender