[logback-user] Separating the logging-output of libraries in tomcat/shared

Ceki Gulcu ceki at qos.ch
Fri Feb 26 11:05:06 CET 2010

Hello Achim,

Thank you for your message.

The only way to solve this issue transparently and perfectly would be
to introduce another level of indirection inside loggers so that each
logger-shell somehow delegate work to an inner logger attached to the
appropriate context. This is quite a difficult problem technically and
would generate significant computational overhead. I don't see the
problem fixed via such indirection any time soon. Read, as a logback
user, don't expect this problem to be solved without a little work on
your side.

As far as I can see, you have two options:

1) move shared classes whose loggers you care about to the web-app
(unshare them)

If 1) is not an option, there is:

2) Use a single shared logback.xml file with separation done by
SiftingAppender [1] using the context as separation criteria [2]. In
conjunction with prudent mode of FileAppender, you will be able to
separate logging by context.

Let me know if the above does not make sense.

[1] http://logback.qos.ch/manual/appenders.html#SiftingAppender

On 26.02.2010 08:21, Achim Wiedemann wrote:
> Hey everybody,
> just wanted to port our application from commons-logging / log4j to
> slf4j / logback. Unfortunately I stumbled upon some problems when
> separating the logging-output from different webapps (using the
> JNDIContextSelector). As long as you only use logging from classes
> inside the webapp, everything works fine. But as soon as you've got
> classes in tomcat/shared which use logging, you run into trouble: All
> logging output of the shared classes (e.g. Spring) are directed to the
> logger-context of the webapp which first loads the (shared) class.
> Example: Let's say you've got webbapp [A], webbapp [B], and Spring in
> tomcat/shared. Now both webapps use Spring. If webapp [B] first accesses
> any classes of Spring, all output of Spring will be directed to the
> log-file of [B], no matter from which webapp Spring is used. This is
> because static Logger references are used in Spring (which is
> commonplace) and are initialized with the context of webapp [B].
> The issue is already described very well in the logback JIRA:
> http://jira.qos.ch/browse/LBCLASSIC-166
> I wondered if anyone can make a suggestion how to deal with this. Any
> advice, tricks or magic is welcome. ;)
> Thanks a lot,
> Achim

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