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From Dain Sundstrom <>
Subject Logging problems
Date Fri, 05 Nov 2004 19:29:07 GMT
After working with geronimo for a while, I am convinced our current 
logging solution was a bad idea (on my part :).  There are several 
problems, so I'll try to categorize them.

Log4j GBeans

Our current log4j gbeans attempt to control the creation of log 
objects, priories... basically the log4j configuration.  The problem I 
have found is any application can come along and "reset" the current 
log4j configuration and reinitialize the system.  I do not believe 
there is any way to prevent this.  It is on of those problems that 
everyone had control which in effect gives no one control.

I propose that we drop all of our gbeans that try to control Log4j and 
instead go to a single gbean that exposes the operations of LogManager, 
and a log4j.xml file (as a big string).  The big string would be a 
persisted to somewhere like var/log4.xml.

Commons LogFactory

Currently all of our code uses commons logging.  The problem is how we 
obtain org.apache.commons.logging.Log implementation.  This is most 
common code in to obtain a Log:

     private static Log log = LogFactory.getLog(MyGBean.class);

The problem is the static LogFactory.  As with log4j above anyone can 
come along an kick out our log factory.  Also, the code we use to setup 
the LogFactory on geronimo boot is very very ugly and error prone.

I propose we make "Log log" a GBean magic attributes, which means that 
is automatically available to all gbeans (just like class loader and 
kernel).  If a gbean declares that it wants a log we will create and 
initialize a log.  This will also let the kernel add additional 
information to log events such as gbean object name.

Commons Log

If we make the above changes, we will only be using the 
org.apache.commons.logging.Log class from commons logging.  The problem 
is to get this class we include a commons-logging jar into geronimo and 
this jar will carry a specific version number.  This means that all 
applications are restricted to use the version of commons logging that 
we ship.

I can think of two solutions this problem: ship only the 
org.apache.commons.logging.Log class with geronimo or repackage Log 
into a geronimo package (say org.apache.geronimo.logging.Log or 
org.apache.geronimo.logging.GLog).  I don't have much of a preference 
for either of these solutions, but I feel we must address this problem.

I'm going to start working on the first proposal above, Log4j, as I 
think it is the least controversial. If you have any concerns about 
that one, please respond sooner rather then later.



Dain Sundstrom
Chief Architect
Gluecode Software
310.536.8355, ext. 26

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