FYI:
you can do the same with Info and Warn (or any other level)
if (log.isInfoEnabled())
{
...
}
and
if (log.isEnabledFor(org.apache.log4j.Level.WARN))
{
...
}
These checks are a good idea if you would conceivably disable a certain logging level,
and the method arguments take runtime effort to construct.
Depending on how often it occurs, JVM specifics, and the size of the strings involved,
string concatenation can be a big deal for both memory and performance.
If you want to eliminate this as a possible cause for sure, try writing a test.
Create a small program that logs a concatenated string a large number of times. Try
it with logging enabled/disabled, and your config. Then modify the test to perform
the appropriate check and retry with logging enabled/disabled. The data should tell
you if the change is significant.
Sean
-----Original Message-----
From: James Gallogly [mailto:[EMAIL PROTECTED]]
Sent: Wednesday, December 18, 2002 3:24 PM
To: Log4J Developers List
Subject: RE: Large Memory usage while using log4j
That is true for our debug level logging, however we also have info level
and warn levels that utilize string concatenation. We do understand we are
paying for the string concatenation of the function call and thus creating
several transient string objects that will be destroyed after the function
call returns. This however should cause performance implications with a
small memory cost. The concern is we are seeing a tremendous memory cost
even though our log4j settings are configured to log nothing.
We use this logging scheme because we have several levels of deployment.
During development test cases are run with debug level, during Official
Testing we run at a level of Info or Warn, and crank it up to debug if
needed (by category), during Release we set our logging to error (which for
us is the same as none). In general our ideology has been one of robustness
and maintainability come before performance however an order of magnitude
memory increase/decrease is something that captures our attention.
Jim
-----Original Message-----
From: Sean Reilly [mailto:[EMAIL PROTECTED]]
Sent: Wednesday, December 18, 2002 4:00 PM
To: Log4J Developers List
Subject: RE: Large Memory usage while using log4j
Just to sanity check....
if you log a message that performs string concatenation, you do it like
this, right?
(assumes an org.apache.log4j.Logger instance log)
if (log.isDebugEnabled())
{
log.debug("Test Log Message: " + foo + " = " + bar + ".");
}
Sean
Sean Reilly
Programmer, Point2 Technologies, Inc.
(306) 955-1855
[EMAIL PROTECTED]
-----Original Message-----
From: James Gallogly [mailto:[EMAIL PROTECTED]]
Sent: Wednesday, December 18, 2002 2:55 PM
To: Log4J Developers List
Subject: RE: Large Memory usage while using log4j
Thanks!! That is a good thread, what concerns me the most however is that
nothing is being logged.
Our logging was set to error (we do no error level logging). This means
that nothing is logged in either case.... does this mean that the Conversion
Pattern is applied before the decision to log or not occurs? In other words
why is log4j using up so much memory to do what should be nothing?
Thanks,
Jim
-----Original Message-----
From: Ceki Gulcu [mailto:[EMAIL PROTECTED]]
Sent: Wednesday, December 18, 2002 3:42 PM
To: Log4J Developers List
Subject: Re: Large Memory usage while using log4j
The following thread might be relevant:
http://marc.theaimsgroup.com/?l=log4j-dev&m=103366188809758&w=2
At 15:35 18.12.2002 -0500, you wrote:
> On my project we have been heavily utilizing log4j as our logging
> solution.
>Recently we ran our code under very heavy load so as part of our
>optimization we wrote code to extract the log4j logging calls from our
>source. We did this in hopes of reducing some of the overhead of
>concatenation strings together thus squeezing out some performance gain.
>
> Much to our surprise the greatest impact was in memory usage, our
> memory
>usage went from 1 gig to 100 meg. This order of magnitude decrease in
>resource usage caught our attention to say the least. How might we be miss
>using the log4j tool to cause such large memory consumption?
>
> We are performing small scale experiments trying to duplicate the
> essence
>of the problem but have had little success so far. Any help or direction
>will be much appreciated.
>
>Thanks,
>Jim
--
Ceki
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