Child threads no longer inherit MDC values. In previous versions of logback as well as log4j 1.x, MDC values were inherited by child threads. Several users have argued convincingly that MDC inheritance by child threads was unhelpful and even dangerous. This change fixes LOGBACK-422 and LOGBACK-624
https://logback.qos.ch/news.html
logback从1.1.5版本之后,新的commit将MDC内部维护的InheritThreadLocal修改成了ThreadLocal,MDC不支持线程继承了。