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From "Shapira, Yoav" <>
Subject RE: [general] logging
Date Fri, 27 Aug 2004 17:04:15 GMT

If you do convert anything, I for one would be interested in performance
benchmarks of this monitor approach compared to C-L and to direct
logging e.g. log4j.  Logging has to be a low-to-negligible performance
cost component.

Yoav Shapira
Millennium Research Informatics

>-----Original Message-----
>From: Alex Karasulu []
>Sent: Friday, August 27, 2004 1:04 PM
>To: Jakarta Commons Developers List
>Subject: Re: [general] logging
>BTW before I begin I wanted to say that C-L is simple and costs
>relatively little.  It does not tie a library to a logging
>implementation and IMHO it gets far too much criticism for the
>convenience it affords us.  Its really an **adapter** for other logging
>implementations and that's it (as Craig pointed out below).  Perhaps
>the fact that this is a dependency on another jar that causes this
>to come up repeatedly as opposed to logging itself.  In the end I don't
>know exactly why it is such a hot topic of debate.
>However I think this issue is one we can resolve if we generalize the
>problem using monitors and event notification.  Logging is just a
>specific application for a monitor. Paul Hammant described this in the
>NoLogging wiki here:
>I think I brought this up before and forgive me for doing it again.  If
>this is annoying anyone I will not discuss it again.  Perhaps I need
>cons against it once more.  However I still do believe that this is the
>best solution for now.
>All a library needs to do is expose a monitor interface to publish the
>notible events that may occur while the library is doing its thang.
>the monitor responds to events by logging them or otherwise is a matter
>of implementation.  A default do-nothing monitor adapter may be
>with the library instead of the dependency on C-L.  Other monitor
>interface implementations, not packaged with the core, can have a C-L
>based logging monitor implementation (hence C-L dependency) that can be
>used out of the box if desired.  Dependencies are minimized, ugly
>logging code is isolated away and all the parties concerned are happy.
>Is this too idealistic a viewpoint?  Perhaps.  I guess I'm offering up
>this approach yet again for others to correct me.
>On Thu, 2004-08-26 at 17:17, Craig McClanahan wrote:
>> You are asking two separate but related quesitons here, so they
>> be addressed separately.
>> (1) Should libraries depend on *any* logging library?
>I believe there should be no dependency at all although I'm comfortable
>with a dep on C-L.  People just get too passionate about dependencies
>now adays.  So why not get rid of the argument by solving all these
>concerns.  The use of a callback monitor interface exposed by these
>libraries would solve the need for any C-L or other dependencies.  Plus
>by generalizing the problem we open the door for many more use cases.
>> (2) If so, what logging library should be used?
>I don't think (1) has to be the case but if it were C-L IMO would be
>absolute best choice for the reasons you've stated below:
>> * Log4J -- but this would force all downstream users of the
>>   library to use Log4J, even if the applications themseves
>>   use something else.
>> * JDK 1.4 -- but this would force all downstream users of
>>   the library to run on JDK 1.4, and also doesn't obey the
>>   "single logging configuration" desire if they are using
>>   something like Log4J
>> * The same basic issue will apply to any other individual
>>   logging implementation you might like -- the selection
>>   of a particular logging API by a commonly reused library
>>   *forces* applications using that library to support that
>>   logging API, even if the app is using something different.
>> Indeed, this issue was the motivation for creating Commons Logging in
>> the first place -- instead of being a logging *implementation* it was
>> deliberately designed as an *adapter* to whatever underlying
>> implementation you want to use.
>Yes this has been said over and over again and I don't understand why
>the debate re-emerges.  Again I can only suspect that its the required
>jar dependecy that is causing most of the concern out there.
>> So, what is it that you are suggesting?
>I would like to add to this.  Is the root of our concerns really the
>fact that we have a dependency on another library or is the issue here
>about a dependency on a logging implemenation?
>If the answer to this Q is yes, the concern is the additional
>and not on a logging adapter or implementation, then using monitors is
>the way to go.  It will do away with the dependency.  Meanwhile it will
>still allow for these libraries to notify users of significant events
>occuring in the library.  If users choose they can then wire up the
>library to a specific logging monitor.  The user still gets to decide
>the end.
>To help demonstrate the application of this NoLogging approach I'm
>volunteering myself to any commons project to convert their C-L
>dependency into a monitor with an associated adapter and other logging
>implementations.  We can make the changes in a branch.  When complete
>can take a step back to look and see if this approach is worth it.  If
>not we can scratch the idea.
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