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From "Ralph Goers (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (LOG4J2-479) Use of InheritableThreadLocal in Map ThreadContext is dangerous and unhelpful
Date Fri, 03 Jan 2014 16:43:55 GMT

    [ https://issues.apache.org/jira/browse/LOG4J2-479?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13861649#comment-13861649
] 

Ralph Goers commented on LOG4J2-479:
------------------------------------

Log4j 1.x used an InheritableThreadLocal for the MDC and a Hashtable with the current thread
as the key for the NDC.  Since the NDC is a Stack it doesn't make any sense for multiple threads
to manipulate it.  I believe Logback used to use an InheritableThreadLocal but does something
different now that has the same effect (it copies the data from the parent thread).  Our implementation
is the same is these for compatibility.  This means you will get the same behavior when you
are using the SLF4J API.  However, this issue has been raised a couple of times on the Logback
and there are open Jira issues for it.  The most logical proposal is one to allow a system
property to control whether the child inherits from its parent.

> Use of InheritableThreadLocal in Map ThreadContext is dangerous and unhelpful
> -----------------------------------------------------------------------------
>
>                 Key: LOG4J2-479
>                 URL: https://issues.apache.org/jira/browse/LOG4J2-479
>             Project: Log4j 2
>          Issue Type: Bug
>            Reporter: MK
>
> Described here http://logging.apache.org/log4j/2.x/manual/thread-context.html
> The use of InheritableThreadLocal creates subtle and hard to track bugs while not really
adding much useful.  It is counterintuitive -- I don't see why would anyone expect logging
context to be inherited.  But it breaks down completely when used with Thread Executors.



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