[logback-user] TurboFilter scope

[Don Griffin]

Firstly, as this is my first post, thanks for an overall great library!

Having just read the section on TurboFilters, they are (almost) just 
what I need. I fear that the way they are implemented puts undue penalty 
and difficulty on their performance.

I did scan the past several months in the archive and did not find any 
mention of TurboFilter, even still, this may be something someone else 
has already suggested. If so, I apologize for the noise. In any case, 
here is my suggestion:

Why not put TurboFilters on Loggers instead of the global context? That 
is, the example from the (very helpful and well done) manual:

   <configuration>
     <turboFilter class="chapter6.SampleTurboFilter">
       <Marker>sample</Marker>
     </turboFilter>

     <appender name="STDOUT" class="...">
       ... snip ...
     </appender>

     <root>
       <appender-ref ref="STDOUT" />
     </root>
   </configuration>

Would change to:

   <configuration>
     <appender name="STDOUT" class="...">
       ... snip ...
     </appender>

     <root>
       <turboFilter class="chapter6.SampleTurboFilter">
         <Marker>sample</Marker>
       </turboFilter>
       <appender-ref ref="STDOUT" />
     </root>
   </configuration>

Almost the same, and it would achieve the same result as the original. 
In my case, however, I could apply a TurboFilter to only the loggers 
that need it:

   <configuration>
     <appender name="STDOUT" class="...">
       ... snip ...
     </appender>

     <root>
       <appender-ref ref="STDOUT" />
     </root>

     <logger name="foo">
       <turboFilter class="chapter6.SampleTurboFilter">
         <Marker>sample</Marker>
       </turboFilter>
     </logger>

     <logger name="foo.bar">
     </logger>
   </configuration>

In this case, the "foo.bar" logger would inherit the TurboFilter from 
the "foo" logger. In essence, each Logger object would have its own 
collection of TurboFilter objects that are the concatenation of any 
filters configured on itself, followed by its parent, grand-parent, etc. 
on up to the root of hierarchy.

This approach should greatly reduce the total penalty for using such a 
powerful mechanism and at the same time give finer grained control over 
which filters apply to which loggers.

Any thoughts?

Best regards,
Don