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From "Ralph Goers (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (LOG4J2-585) Markers not as powerful as slf4j
Date Sat, 05 Apr 2014 16:32:15 GMT

    [ https://issues.apache.org/jira/browse/LOG4J2-585?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13961145#comment-13961145
] 

Ralph Goers commented on LOG4J2-585:
------------------------------------

No - I was referring to Bruce's suggestion to use a volatile reference to an array.  I implemented
that last night. 

The more I think about it the more I like the idea that parents added on the constructor cannot
be removed. 



> Markers not as powerful as slf4j
> --------------------------------
>
>                 Key: LOG4J2-585
>                 URL: https://issues.apache.org/jira/browse/LOG4J2-585
>             Project: Log4j 2
>          Issue Type: Improvement
>          Components: API
>    Affects Versions: 2.0-rc1
>            Reporter: Bruce Brouwer
>         Attachments: ConceptMarkerBenchmark.java, CurrentMarkerBenchmark.java, log4j2-585-concept.patch
>
>
> Log4J's markers are not as flexible as markers in SLF4J. 
> First, SLF4J's markers are mutable. By allowing markers to be mutable, I can change the
relationship of markers to each other based upon runtime or business conditions. 
> Second, and more importantly I think, is that essentially SLF4J markers have this parent/child
relationship, much like Log4J, except that in SLF4J, I can essentially have a marker with
multiple parents. For example, I might want this structure:
> * Animal
> ** Bird
> *** Duck
> ** Mammal
> *** Bear
> *** Dolphin
> * Travels by
> ** Water
> *** Duck
> *** Dolphin
> ** Land
> *** Duck
> *** Bear
> ** Air
> *** Duck
> Of course, this is a contrived example, but I wanted to describe the relationships. Now,
if I wanted to filter based on markers that travel by Water for some appenders, and another
appender wants to filter by Mammals, I can't simply use the single marker of Dolphin. 
> Either we need to reverse the marker relationship so that it contains its children, much
like SLF4J, or we allow markers to have multiple parents, which I prefer because it could
make it more succinct to define:
> {code}
> private static final Marker BY_LAND = MarkerManager.getMarker("BY_LAND");
> private static final Marker BY_WATER = MarkerManager.getMarker("BY_WATER");
> private static final Marker DUCK = MarkerManager.getMarker("DUCK", BY_LAND, BY_WATER);
> {code}
> As for the Marker API, we would either need to change getParent to getParents, or get
rid of the getParent method from the API and just rely on the isInstanceOf method to handle
checking multiple parents by looking at private member variables (my preference)



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