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From chandra.swaminat...@kodak.com
Subject Re: automatic trace insertion
Date Wed, 19 Dec 2001 22:03:45 GMT

From: Chandra Swaminathan

Tom,

Can you provide some more detail (possibly an example) on the java Proxy
class that you are talking about and how exactly it helps to get the
performance loss to 0.  I was interested in your suggestion but don't know
how this can be implemented.  Is it possible to do it without re-compiling
the application?

Chandra.





"Tom Eugelink" <tom_eugelink@hotmail.com> on 12/19/2001 12:37:59 AM

Please respond to "Log4J Developers List" <log4j-dev@jakarta.apache.org>

To:   log4j-dev@jakarta.apache.org
cc:
Subject:  Re: automatic trace insertion


As a "I just stumbled into the Log4J developer list because maybe..."
reader
of these emails, but still a seasoned developer (15+ years), I do feel
inclined to make a few comments on logging:

1. You never know (when writing code) what you want to log, because you do
not know what problem you will be solving.
2. Adding logging code ALWAYS has a performance penalty (even if it is only
an IF statement). Most ideally logging code can be deactivated completely
until it is needed.

Based on the first statement you would want to add as many Log4J lines as
possible, of course with good categories, so you can figure out what is
going on. This is INCLUDING setters and getters, just to make sure data has
gotten where it should be going.

And this is of course in conflict with the second statement. That is why I
often use the Proxy class in java (this class automatically wraps around an
interface and provides a hook for all methods, from where I call Log4J).
The
wrapper is only created when logging is enabled, thus resulting in 0
performance loss when debugging is off.

Now, it seems to me that the Jylog does something similar: if not logging,
no listener is present, so no performance penalty (the logging feature is
always present in the JVM). And since Log4J suggest using categories that
resemble the package structure, filtering log data on package structure
should come very close to this approach.

In other words: I am charmed by the Jylog idea. Not new (because all IDE
use
it) but interesting because it focuses on logging.

Tom



>From: Benson Chen <benson@porivo.com>
>Reply-To: "Log4J Developers List" <log4j-dev@jakarta.apache.org>
>To: Log4J Developers List <log4j-dev@jakarta.apache.org>
>Subject: Re: automatic trace insertion
>Date: Tue, 18 Dec 2001 13:38:50 -0500
>
>Vincent,
>
>Yup, I don't doubt that that's the way to do it.... nice clean separation
>of
>logic and data.  In order to make sense of the trace, everyone has to make
>sure that the toString() method is implemented for each data object.
>Actually
>this leads to another question (which might need another thread)... does
>anyone know of some code that automatically creates toString() methods?
>Possibly using reflection to get instance variables and fills in the
>toString() method for you.  As you can see, I'm a proponent of any form of
>automation... maybe because I'm lazy.  :-)  -Benson
>
>Vincent Massol wrote:
>
> > In our case, the data objects are just that ... data objects. These
> > objects are manipulated by business methods (they are passed as
> > parameters or returned). As you can seem, the AspectJ code I have
> > provided does log all the parameters using the toString()
representation
> > of an object. So each of our object has a printable toString method.
> >
> > -Vincent
> >
> > > -----Original Message-----
> > > From: bchen@porivo.com [mailto:bchen@porivo.com] On Behalf Of Benson
> > Chen
> > > Sent: 18 December 2001 17:15
> > > To: Log4J Developers List
> > > Subject: Re: automatic trace insertion
> > >
> > > Well sometimes logging those setter methods are just as important
> > because
> > > you
> > > want to know as you trace through your code that some object's state
> > has
> > > been
> > > modified.  As to solve the volume problem, I wouldn't enable logging
> > to
> > > your
> > > whole system all at once unless of course you are doing system
> > testing.
> > > The
> > > beauty of log4j is that you can have all sorts of categories (one for
> > each
> > > class) to allow you to enable or disable traces depending on what you
> > are
> > > interested in and the amount of volume you want to deal with.
> > > Actually, one thing I was thinking about was having some sort of
> > > intelligent
> > > trace enablement where all traces are disabled by default but if a
> > > RuntimeException is thrown, you have code that goes through the stack
> > > trace
> > > and enables trace logs for classes/methods leading up to the
> > exception.
> > > This
> > > way when you run your system again, you'll have logs tailored to
> > watching
> > > exactly what events occurred before your system blew up.
> > > Again, I'm not dictating how you should use log4j, but I would think
> > that
> > > being able to easily get at more information is always best.  But
> > using
> > > log4j
> > > in any capacity is better than none at all.  :-)  -Benson
> > >
> > > Vincent Massol wrote:
> > >
> > > > You are right, Paul, it is important not to log everything, as logs
> > tend
> > > > to grow big very quickly and performance suffer a lot. In my
project
> > we
> > > > use AspectJ to log entries and exits with the following rules :
> > > >
> > > > - public methods that accept at least one parameter (static and
> > > > non-static),
> > > > - exclude the data object packages (we have all our data objects -
> > > > setter/getter objects - located in a package)
> > > >
> > > > These rules seem to strike a good balance (at least for us). Then,
> > we
> > > > use the log4j configuration to turn on/off logging for specific
> > > > categories.
> > > >
> > > > -Vincent
> > > >
> > > > > -----Original Message-----
> > > > > From: Paul Glezen [mailto:pglezen@us.ibm.com]
> > > > > Sent: 18 December 2001 15:07
> > > > > To: Log4J Developers List
> > > > > Subject: RE: automatic trace insertion
> > > > >
> > > > > Scott brings up an important point.  Do you really want to trace
> > every
> > > > > method?  Even simple getters/setters?  Not only will there be a
> > > > > performance
> > > > > penalty (acceptable in some circumstances), it would also create
> > more
> > > > > volume than you might want.
> > > > >
> > > > > Paul Glezen
> > > > > Consulting IT Specialist
> > > > > IBM Software Services for WebSphere
> > > > > 818 539 3321
> > > > >
> > > > >
> > > > > Scott Coleman <scott.coleman@soltima.com> on 12/18/2001 06:57:50
> > AM
> > > > >
> > > > > Please respond to "Log4J Developers List"
> > > > <log4j-dev@jakarta.apache.org>
> > > > >
> > > > > To:   "'Log4J Developers List'" <log4j-dev@jakarta.apache.org>
> > > > > cc:
> > > > > Subject:  RE: automatic trace insertion
> > > > >
> > > > >
> > > > >
> > > > > Hi,
> > > > >
> > > > > I have not read the whole article yet, but I think you will get a
> > > > heavy
> > > > > performance penalty if you use JPDA.
> > > > > Can someone please explain to me why you would want to log both
> > entry
> > > > and
> > > > > exit calls, for such a thin layer in the code. I thought that it
> > was
> > > > meant
> > > > > to be very fast. So why would you want to add the performance
> > overhead
> > > > of
> > > > > logging entry and exit information. If you were to go down this
> > path
> > > > would
> > > > > it not be better to use jdk 1.4's new assert feature ?
> > > > >
> > > > > Regards
> > > > > Scott
> > > > >
> > > > > -----Original Message-----
> > > > > From: Cakalic, James [mailto:James.Cakalic@heybridge.com]
> > > > > Sent: Monday, December 17, 2001 11:37 PM
> > > > > To: 'Log4J Developers List'
> > > > > Subject: RE: automatic trace insertion
> > > > >
> > > > >
> > > > > This article about Jylog -- a JPDA based logging generator --
just
> > > > > appeared
> > > > > on JavaWorld. Perhaps it relevant?
> > > > >
> > http://www.javaworld.com/javaworld/jw-12-2001/jw-1214-jylog.html
> > > > >
> > > > > Jim
> > > > >
> > > > > > -----Original Message-----
> > > > > > From: Paul Glezen [mailto:pglezen@us.ibm.com]
> > > > > > Sent: Monday, December 17, 2001 4:25 PM
> > > > > > To: Log4J Developers List
> > > > > > Subject: Re: automatic trace insertion
> > > > > >
> > > > > >
> > > > > > Hi Benson,
> > > > > >
> > > > > > It's not as easy as it looks to do "intelligently".  While it
is
> > > > often
> > > > > > taught that methods should have a single entry point and exit
> > > > > > point, not
> > > > > > many programmers adhear to this.  It is not at all uncommon
> > > > > > to find return
> > > > > > statements in if-blocks and try-catch blocks.  Sometimes the
> > > > > > exit logic can
> > > > > > get very convoluted.
> > > > > >
> > > > > > I've always been partial to single exit logic.  I didn't
> > > > > > become a fan until
> > > > > > trying to insert trace statements, just as you describe, in
> > > > > > other people's
> > > > > > code.  It can be a nightmare.
> > > > > >
> > > > > > - Paul
> > > > > >
> > > > > > Paul Glezen
> > > > > > Consulting IT Specialist
> > > > > > IBM Software Services for WebSphere
> > > > > > 818 539 3321
> > > > > >
> > > > > >
> > > > > > Benson Chen <benson@porivo.com>@porivo.com on 12/17/2001
> > 01:57:15 PM
> > > > > >
> > > > > > Please respond to "Log4J Developers List"
> > > > > > <log4j-dev@jakarta.apache.org>
> > > > > >
> > > > > > Sent by:  bchen@porivo.com
> > > > > >
> > > > > >
> > > > > > To:   log4j-dev@jakarta.apache.org
> > > > > > cc:
> > > > > > Subject:  automatic trace insertion
> > > > > >
> > > > > >
> > > > > >
> > > > > > Hi all,
> > > > > >
> > > > > > I'm interested in automatically inserting log4j trace
> > > > > > statements at the
> > > > > > beginning of all methods and right before the end of a method
> > > > (return
> > > > > > statement or thrown exception).  I'm presuming most people have
> > > > worked
> > > > > > on projects with extensive class libraries and it would be
great
> > if
> > > > > > there was a class parser that could intelligently insert log4j
> > > > > > statements automatically.  If there isn't anything out there
> > > > > > like that,
> > > > > > does anyone know of a java class parser that can be used to
> > > > > > do this sort
> > > > > > of thing?  Thoughts or ideas?  Thanks!
> > > > > >
> > > > > > --
> > > > > > Benson Chen
> > > > > > Director of Software Engineering
> > > > > > Porivo Technologies, Inc.
> > > > > > Phone: (919)806-0566x12
> > > > > > E-Mail: benson@porivo.com
> > > > > > "Measuring end-to-end Web performance"
> > > > > >
> > > > > >
> > > > > >
> > > > > >
> > > > > > --
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> > > > > >
> > > > > >
> > > > > >
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> > > --
> > > Benson Chen
> > > Director of Software Engineering
> > > Porivo Technologies, Inc.
> > > Phone: (919)806-0566x12
> > > E-Mail: benson@porivo.com
> > > "Measuring end-to-end Web performance"
> > >
> > >
> > >
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>
>--
>Benson Chen
>Director of Software Engineering
>Porivo Technologies, Inc.
>Phone: (919)806-0566x12
>E-Mail: benson@porivo.com
>"Measuring end-to-end Web performance"
>
>
>
>
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>
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>
>


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