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http://jira.qos.ch/browse/LBCLASSIC-87?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Ceki Gulcu closed LBCLASSIC-87.
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> LoggerContextFilter is useless (org.slf4j.Loggerfactory bug ++)
> ---------------------------------------------------------------
>
> Key: LBCLASSIC-87
> URL: http://jira.qos.ch/browse/LBCLASSIC-87
> Project: logback-classic
> Issue Type: Bug
> Components: Other
> Affects Versions: unspecified
> Environment: Operating System: All
> Platform: All
> Reporter: Jens Elkner
> Assignee: Logback dev list
>
> Since LoggerFactory obtains the LoggerContext to use in its static init
> stage, using a LoggerContextFilter as described in Chapter 8 is completely
> useless, since the JNDI selector is never consulted again.
> Digging deeper on that issue reveals, that using a ContextJNDISelector (even
> if it would work) rarely leads to the intended behavior (e.g. webapp related
> logging), and is probably not thread safe wrt. common practice and intended
> logging. E.g. in tomcat we have two different cases:
> a) each webapp provides its own slfj4*.jar as well as *logback*.jar
> b) slfj4*.jar as well as *logback*.jar are shared via tomcat/common/lib or
> tomcat/share/lib
> c) a und b mixed
> Well, to get things right, one can say case c) is unsupported ;-).
> In case a) logback has its own playground, so using JNDI doesn't make sense
> at all, since the webapp/logback has its own playground - doesn't interfere
> with
> other web apps since loaded via its dedicated classloader.
> However case b) is a little bit more challenging. Here the LoggerFactory and
> other classes are !shared! between several webapps, since loading is
> delegated from the dedicated webapp classloader to the shared webapp
> classloader, which picks up everything in share/lib , common/lib. So right
> now in 0.9.7, even if one uses JNDISelector a per webapp logging is
> impossible: The first webapp, which asks for a LoggerFactory always wins! All
> other webapps, which ask later for a LoggerFactory.getLogger() will get a
> Logger from the LoggerContext associated with the first webapp, since the
> context is "cached", i.e. the JNDI selector gets never consulted again.
> Assuming the LoggerFactory problem gets fixed by using e.g.
> public static Logger getLogger(* *) {
> return StaticLoggerBinder.SINGLETON.getLoggerFactory().getLogger(**);
> }
> there is still a problem wrt. common practice aka log* usage pattern and
> webapp shared classes, which can not be resolved by JNDI: Today most
> developer use something like:
> public class XY {
> private static [final] Logger log = LoggerFactory.getLogger(XY.class);
> ...
> }
> That implies the same problem, as with the current LoggerFactory bug: The
> class gets the Logger from the context associated with the first webapp,
> which needs the shared class. And that's why all other webapps, which later
> need this class will use the the logger context of the first webapp. So e.g.
> if webapp A is configured to log to /var/log/a.log and another webapp B is
> configured to log to /var/log/b.log the loging output of shared classes will
> always go to /var/log/a.log if webapp used the classes in question first, no
> matter on which thread aka in which webapp the shared classes are used.
> So even if LoggerFactory gets fixed, JNDI selector is of little use, if one
> wants to have a webapp dedicated log as soon as shared classes are involved.
> The only way to solve the didcated webapp log problem a can think of, to
> introduce another level of indirection in the Logger.log* etc. method, which
> takes care of thread local settings and the settings of its parent threads
> (e.g. an application may start other threads, which do not inherit the thread
> local settings from the current thread ...). But this would probably
> influence the performance of logback in a rather negative way.
> Another idea might be an architecture re-design: sharing Loggers would be no
> problem because of thread local AppenderContext soft ref, which points to an
> Appender in the global AppenderStore singleton ...
> RFE: These problems should be reflected chapter 8 of the logback manual to
> avoid further confusion ...
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