[logback-user] Different Log Levels For Different Appenders?

Eric Faden eric at techeminence.com
Thu Aug 28 18:21:36 CEST 2008

Seems reasonable.  I was just double checking that it was the correct 
way to do it.  Thanks.


Ceki Gulcu wrote:
> Contrary to log4j, logback appenders do not automatically inherit a threshold 
> filter. You probably don't care but this has to do with the fact that the 
> functionality offered by log4j is assumed by two separate modules, logback-core 
> and logback-classic. Logback-core, where several appenders (e.g. FileAppender) 
> are defined, does not really know about logging. Both the Logger and Level 
> classes are defined in logback-classic and not in logback-core. In order to 
> avoid duplicated code, FileAppender is defined only in logback-core and not in 
> logback-classic. It's LoggingEvent specific layouts and filters defined in 
> logback-classic that give a FileAppender instance its "logging-aware" behavior.
> Anyway, to cut a long story short, it could have been possible to redefine 
> FileAppender in logback-classic in order to add a threshold-filter. But as it is 
> possible to accomplish the same by setting a "c.q.l.clas.filter.ThresholdFilter"
> in a configuration file, we traded shorter configuration syntax in favor of not 
> not duplicating code.
> Anyway, see logback-examples/src/main/java/chapter6/ThresholdFilterConfig.xml 
> for an example. It really has the same effect as the threshold keyword in log4j.
> Rob Ross wrote:
>> I also wanted to do exactly what you are trying to do. I discovered  
>> the only way to do this is with a filter on the appender, instead of  
>> being able to set the Level on the appender as you could do with log4j.
>> I don't know yet which method is "better", but the ability to set a  
>> filter on the appender does give me the same end-result as with  
>> log4j, so I am satisfied with this method.
>> Rob Ross, Lead Software Engineer
>> E! Networks
>> ---------------------------------------------------
>> "Beware of he who would deny you access to information, for in his  
>> heart he dreams himself your master." -- Commissioner Pravin Lal
>> On Aug 28, 2008, at 7:01 AM, Eric Faden wrote:
>>> That doesn't exactly solve what I am trying to do.  The problem isn't
>>> that I can't get the correct level on a specific logger, the  
>>> problem is
>>> more that I want to have a specific logger go to two different  
>>> appenders
>>> and log at different levels based on the appender.  For example I want
>>> to have the root logger log at level INFO to the Console.  I then want
>>> to have the logger for some class Blah log to the appender for root
>>> (Console) at the level of root (INFO), but also log to a file  
>>> Foo.txt at
>>> level Debug.  So far as I can tell the only way to do this is to  
>>> set the
>>> level of Blah to debug, have a file appender, and also put a filter on
>>> the console appender to filter out things below INFO.  Does that make
>>> sense what I am trying to do?  Basically I want a single logger to log
>>> to different levels to different appenders.
>>> -Eric
>>> Ceki Gulcu wrote:
>>>> Hello Eric,
>>>> I think this is described in chapter 3 of the manual. See "Example  
>>>> 3.9: Logger
>>>> level sample (logback-examples/src/main/java/chapter3/ 
>>>> sample4.xml)". The list
>>>> numbering in that chapter only works with Firefox. So on other  
>>>> browsers you
>>>> might see all examples numbered as "3.". See also the next section  
>>>> in the same
>>>> chapter, on "Configuring Appenders", in particular, the cumulative  
>>>> addition of
>>>> appenders. It might be the other "cleaner" way, you are looking for.
>>>> HTH,
>>>> Eric Faden wrote:
>>>>> So suppose I set my root logger to error, but I want to have another
>>>>> logger operate at debug level.  When I do that it makes that loggers
>>>>> level debug for all appenders.  For example take the following
>>>>> <configuration>
>>>>>   <appender name="*FILE*"
>>>>>      ....
>>>>>   </appender>
>>>>>   <appender name="*STDOUT*"
>>>>>      ...
>>>>>   </appender>
>>>>>   <logger name="mylogger">
>>>>>     <level value="debug" />
>>>>> **    <appender-ref ref="FILE" />**
>>>>>   </logger>
>>>>>   <root>
>>>>>     <level value="error" />*
>>>>>     <appender-ref ref="STDOUT" />*
>>>>>   </root>
>>>>> </configuration>
>>>>> In this example mylogger would output at debug level to BOTH STDOUT
>>>>> and FILE.  Is it possible to only get mylogger to output at debug
>>>>> level to FILE and error to STDOUT?  I realize that I can add a  
>>>>> filter
>>>>> to the STDOUT appender to filter anything below ERROR, but I was
>>>>> curious if there was another way to do this, possibly cleaner?
>>>>> -Eric
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