Weird behavior for RollingFileAppender

["Alex Qi (yuqi)" <yu...@cisco.com>]

I defined a RollingFileAppender in my log4j config file, it works fine
for simple logging request. But when many loggers writing to the same
log file, it behaves like this:
 
original log file is:  "foo.log", it should roll to "foo.log.1",
"foo.log.2"
 
now, "foo.log" did roll to "foo.log.1", but the new message also write
to "foo.log.1" instead of the newly generated "foo.log"
 
Is this a known bug? Thanks. 
 

Regards,

-- Alex Qi

 

 

Re: Weird behavior for RollingFileAppender

[Curt Arnold <ca...@apache.org>]

On Jan 24, 2008, at 1:13 PM, Alex Qi (yuqi) wrote:

> I defined a RollingFileAppender in my log4j config file, it works fine
> for simple logging request. But when many loggers writing to the same
> log file, it behaves like this:
>
> original log file is:  "foo.log", it should roll to "foo.log.1",
> "foo.log.2"
>
> now, "foo.log" did roll to "foo.log.1", but the new message also write
> to "foo.log.1" instead of the newly generated "foo.log"
>
> Is this a known bug? Thanks.
>
>
> Regards,
>
> -- Alex Qi
>

That is a very common behavior when you have more than one appender  
attempting to use the same file name pattern.  It should not occur if  
you only have one appender.  If the same configuration file is loaded  
by multiple independent instances of log4j (for example, in different  
JVM's or class loaders), there will be multiple independent  
implementations of the appender and there is no attempt (or any good  
mechanism to attempt) to coordinate their behavior.

Writing to "foo.log.1" would occur when one instances of the appender  
has rolled over and renamed the old "foo.log" to "foo.log.1".  That  
appender would have closed its output stream on the old file and  
opened a new one on the new file.  A different appender would not be  
aware of that rollover and would continue to write to the same output  
stream that it always, but the name of the file resource that that  
stream is associated with has changed underneath it.  On a Windows  
box, the rename on the rollover would have likely failed, but Unix  
like OS's allow open files to be renamed.

If you configuration file has multiple instances of RFA with the same  
pattern, you either need to reduce those to one instance or change the  
patterns on the instances.  If you are running under an application  
server (Tomcat, JBOSS, etc), the location of the log4j.jar can  
determine if a common instance is used for all applications or if  
multiple instances are used. 

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