Well, the behavior of setLevel() in Log4j 1 in conjunction with logger 
hierarchies ... is unexpected, yes. ;-)

So there is no public(ly supported) way to change a Logger's level in Log4j 2 - 
okay, I'll just miss it.

We've got an API here offering some public documented our.own.Logger instances 
- including a setLevel() method at the public interface, Log4j 1 is one of the 
logging implementations supported.
I think we could implement a work around for our setLevel() method, when we 
want or have to support Log4j 2 - behind the scenes we could create multiple 
Logger instances for the same logical name but the appropriate Logger level and 
redirect to the correct one then. Not perfect but could work.

Just found, the creation of Logger instances seems not to support specifying 
the level directly/programmatically ... aha, there seems to be a way via an own 
LoggerConfig implementation. :-)

Thank you, Ralph!
   Merten

-----Original Message-----
From: Ralph Goers [mailto:[email protected]] 
Sent: Wednesday, July 23, 2014 5:26 PM
To: Log4J Users List
Subject: Re: Logger.setLevel() not supported in 2.0?

In Log4j 2 Logger.setLevel() might now work the way you would expect.  It would 
change the level of the specific logger, but it would not affect child loggers. 
 So if you had a Logger(com.foo) and Logger(com.foo.bar), which both had 
effective levels of "error" and then you called setLevel on Logger(com.foo) 
with "debug", events logged to Logger(com.foo.bar) would still be at "error".  
To change the level in a manner similar to Log4j 1 you would want to obtain the 
appropriate LoggerConfig, change its Level and then call the LoggerContext's 
updateLoggers() method.  Needless to say, this is not something that is exposed 
at the API layer and ties you to the specifics of how Log4j 2 is implemented.

FWIW, changing the Level of the LoggerConfig is supported via JMX, so you can 
create tooling that interacts with that.

Ralph

On Jul 22, 2014, at 11:32 PM, Merten Schumann <[email protected]> wrote:

> Hello,
> 
> from "Converting to the Log4j 2 API":
> Calls to org.apache.log4j.Logger.setLevel() or similar methods are not 
> supported in the API.
> Applications should remove these.
> 
> Could imagine the reason, checking getLevel() is final, so it's quick.
> But, when you have in your program your good old fixed static Logger log, 
> it's often helpful to toggle its logger level at runtime, when the method 
> that should be investigated is reached in the code or in the debugger ... 
> enable DEBUG output and disable it again ...
> 
> Am I missing something? Nobody else missing this feature? :-)
> 
> Thanx
>   Merten


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