Thanks Jean-Baptiste, https://issues.apache.org/jira/browse/KARAF-6219 Routing appender works fine.
Just in case others needed: log4j2.rootLogger.appenderRef.Sift.ref = Routing # Sift - MDC routing log4j2.appender.routing.type = Routing log4j2.appender.routing.name = Routing log4j2.appender.routing.routes.type = Routes log4j2.appender.routing.routes.pattern = \$\$\\\{ctx:bundle.name\} log4j2.appender.routing.routes.bundle.type = Route log4j2.appender.routing.routes.bundle.appender.type = RollingRandomAccessFile log4j2.appender.routing.routes.bundle.appender.name = Bundle-\$\\\{ctx:bundle.name\} log4j2.appender.routing.routes.bundle.appender.fileName = ${karaf.log}/bundle-\$\\\{ctx:bundle.name\}.log log4j2.appender.routing.routes.bundle.appender.filePattern = ${karaf.log}/bundle-\$\\\{ctx:bundle.name\}-%d{yyyy-MM-dd}-%i.log.gz log4j2.appender.routing.routes.bundle.appender.append = true log4j2.appender.routing.routes.bundle.appender.layout.type = PatternLayout log4j2.appender.routing.routes.bundle.appender.layout.pattern = ${log4j2.pattern} log4j2.appender.routing.routes.bundle.appender.policies.type = Policies log4j2.appender.routing.routes.bundle.appender.policies.size.type = SizeBasedTriggeringPolicy log4j2.appender.routing.routes.bundle.appender.policies.size.size = 8MB -- Sent from: http://karaf.922171.n3.nabble.com/Karaf-Dev-f930721.html