Re: JCL vs SLF4J

[Doug Cutting <cu...@apache.org>]

Eric Baldeschwieler wrote:
> I find our current use of apache commons while depending on specific 
> features of log4j awkward.

Yes, this isn't ideal, but an advantage is that, should we switch to a 
different backend, we only need change the few log4j-specific bits, and 
not every line that logs something.  That's significant.

I have used the JVM's built-in logging and found it lacking.  That's 
what the Hadoop code used initially, and we switched to Commons so that 
we could access log4j's features, and also retain the possibility of 
switching again without having to edit every file.

Torsten Curdt wrote:
> IMHO logging facades are better suited for frameworks ...less useful for applications.

Hadoop is in large part a framework.  We'd like applications that use 
different logging frameworks to be able to use Hadoop.  Ideally the 
log4j-specific bits in Hadoop would be isolated to things like startup 
scripts and main() routines, and not directly used in daemon classes, so 
that one could start a Hadoop cluster using a different logging system 
by, e.g., using different startup scripts and main() routines.  We've 
not maintained that sanctity, but if a contributor does arrive who is 
invested in a different logging framework, it would currently not be too 
hard to repair things to support multiple logging mechanisms.  We should 
think twice before losing that possibility.

As things like KFS arrive on the scene it is all the more important to 
keep Hadoop modular.  Mapreduce and HDFS should be kept independent. 
For example, if a site wishes to use mapreduce on top of KFS, and if KFS 
supports a different logging mechanism, then it will be convenient if 
the mapred code does not presume a specific logging implementation.

Doug

Re: JCL vs SLF4J

[Lukas Vlcek <lu...@gmail.com>]

Hi,

I didn't follow the whole debate in Hadoop mail list about SLF4J vs JCL so
my comment may be irrelevant. However, apart of class loader issues in JCL,
did anybody considered performance benefits of SLF4J over JCL?
I have switched to SLF4J recently and I found it very handy. Especially the
syntaxt: log.debug("This must have {} performance then {}", "better",
"JCL");

Regards,
Lukas

On 10/1/07, Doug Cutting <cu...@apache.org> wrote:
>
> Michael Stack wrote:
> > Doug Cutting wrote:
> >> I have used the JVM's built-in logging and found it lacking.
> > Do you remember what the holes in JUL were?
>
> Sorry, I don't remember all the details.
>
> I note that Hadoop uses log4j's DailyRollingFileAppender, and nothing
> like that is present in JUL.  And log4j's formatting options are much
> more sophisticated than JUL's SimpleFormatter.  Also, with log4j, it's
> easy to configure debug logging for a subset of code, based on package
> wildcards.  Such things can be accomplished with JUL, but through the
> addition of code, while log4j moves most of that to the config.
>
> Doug
>



-- 
http://blog.lukas-vlcek.com/

Re: JCL vs SLF4J

[Doug Cutting <cu...@apache.org>]

Michael Stack wrote:
> Doug Cutting wrote:
>> I have used the JVM's built-in logging and found it lacking.
> Do you remember what the holes in JUL were?

Sorry, I don't remember all the details.

I note that Hadoop uses log4j's DailyRollingFileAppender, and nothing 
like that is present in JUL.  And log4j's formatting options are much 
more sophisticated than JUL's SimpleFormatter.  Also, with log4j, it's 
easy to configure debug logging for a subset of code, based on package 
wildcards.  Such things can be accomplished with JUL, but through the 
addition of code, while log4j moves most of that to the config.

Doug

Re: JCL vs SLF4J

[Michael Stack <st...@duboce.net>]

Doug Cutting wrote:
> I have used the JVM's built-in logging and found it lacking.
Do you remember what the holes in JUL were?  Hadoop needed the extra 
facility provided by log4j's PatternLayout or it needed some of the more 
exotic appenders?  Or was it something else? (I don't see anything in 
archives -- maybe I'm searching on wrong thing).

Otherwise, the rest of your mail answers my original question as to why 
hadoop suffers the commons-logging pain.

St.Ack