Log4j and Threadsafeness

["Heupel, Sebastian" <Se...@sdm.de>]

Hallo, 

thought that log4j is thread safe. Now I noticed the following in my Web application (Weblogic Express 6.1) during concurrent access of a Servlet 

* Logfile 

... 
2003-04-14 16:17:48,705, < data to log > 
2003-04-14 16:17:49,705, < data to log > 
2003-04-14 16:17:50,705, < data to log > 
2003-04-14 16:17:51,705, < data to log > 
2003-04-14 16:17:52,705, < data to log > 
> ... and suddenly this piece of text: 
-04-14 16:17:52,705, < data to log > 
... 
2003-04-14 16:17:55,705, < data to log > 
2003-04-14 16:17:56,705, < data to log > 

the same is happening when logging exceptions - only a part of the stack trace is logged. The rest seems to be overwritten ... 

* Log4j Configfile 

log4j.rootLogger=DEBUG, logfile 
log4j.logger.com.bmw.xcaesar.xlogging.XBenchmark=INFO 

log4j.appender.logfile=org.apache.log4j.FileAppender 
log4j.appender.logfile.File=${logFileName} 

log4j.appender.logfile.layout=org.apache.log4j.PatternLayout 
log4j.appender.logfile.layout.ConversionPattern=%d, %m%n 

* and the code 

protected void doGet(HttpServletRequest aRequest, HttpServletResponse aResponse) 
    throws ServletException, java.io.IOException 
    { 
        HttpSession session = aRequest.getSession(true); 
        synchronized (session) 
        { 
           // ... perform the request 
           ... 
       mLogging.debug(logString); 
        } 
    } 

Anybody who knows about this ? All I heard was that log4j is thread-safe. Perhaps this happens because the application runs in a clustered environment ?

Thanks, 
Sebastian




---
Sebastian Heupel          mailto:Sebastian.Heupel@sdm.de <ma...@sdm.de> 
sd&m  AG                    http://www.sdm.de <http://www.sdm.de> 
software design & management
Thomas-Dehler-Str. 27, 81737 Muenchen, Germany
Tel +49 89 63812-265  Fax -490