On Feb 11, 2008 9:40 AM, Maarten Bosteels <[EMAIL PROTECTED]> wrote:
> Hello Nathan,
>
> I guess this is what is happening:
> * one thread is writing a loggingEvent to the log file,
> => the PatternParser calls toString() on all MDC values and hence iterates
> over the elements in your TreeMap
> * at the same time another thread updates the TreeMap
> causing a java.util.ConcurrentModificationException in the first thread.
>
> To avoid this type of problems, I would advise to only put String objects
> in the MDC.
>
> MDC.put("map", myTreeMap.toString());
> instead of
> MDC.put("map", myTreeMap);
>
I just realized that this could cause an ConcurrentModificationException
just as well :-)
Bottom line: when you access a mutable object from multiple threads you need
some kind of synchronization.
Maarten
> Maarten
>
>
> On Feb 11, 2008 12:38 AM, Nathan Clement <[EMAIL PROTECTED]>
> wrote:
>
> > Hi,
> >
> > I've examined this exception further, and it seems to be caused by the
> > fact that I'm using a non-synchronized TreeMap in the MDC. I don't
> > understand why this would cause an issue seeing as the MDC uses a
> > ThreadLocalMap, so synchronization should be unnecessary. However, I've
> > replaced the TreeMap with a synchronized map and will hope that the error
> > doesn't occur any more.
> >
> > Regards,
> >
> > Nathan
> >
> > ----- Original Message ----
> > From: Nathan Clement <[EMAIL PROTECTED]>
> > To: [email protected]
> > Sent: Friday, 8 February, 2008 2:17:57 PM
> > Subject: Uncaught Exception in Log4J 1.2.15
> >
> > Hi,
> >
> > I got this uncaught exception in our production system and am sending it
> > to this list as per the FAQ. Do you need any more information to locate the
> > problem?
> >
> > Thanks,
> >
> > Nathan
> >
> > java.util.ConcurrentModificationException
> > at java.util.TreeMap$PrivateEntryIterator.nextEntry(TreeMap.java:1031)
> > at java.util.TreeMap$EntryIterator.next(TreeMap.java:1052)
> > at java.util.TreeMap$EntryIterator.next(TreeMap.java:1050)
> > at java.util.AbstractMap.toString(AbstractMap.java:587)
> > at org.apache.log4j.helpers.PatternParser$MDCPatternConverter.convert(
> > PatternParser.java:467)
> > at org.apache.log4j.helpers.PatternConverter.format(
> > PatternConverter.java:65)
> > at org.apache.log4j.PatternLayout.format(PatternLayout.java:502)
> > at org.apache.log4j.WriterAppender.subAppend(WriterAppender.java:302)
> > at com.metiom.system.DailyFileAppender.subAppend(DailyFileAppender.java
> > :321)
> > at org.apache.log4j.WriterAppender.append(WriterAppender.java:160)
> > at org.apache.log4j.AppenderSkeleton.doAppend(AppenderSkeleton.java:251)
> > at org.apache.log4j.helpers.AppenderAttachableImpl.appendLoopOnAppenders
> > (AppenderAttachableImpl.java:66)
> > at org.apache.log4j.Category.callAppenders(Category.java:206)
> > at org.apache.log4j.Category.forcedLog(Category.java:391)
> > at org.apache.log4j.Category.debug(Category.java:260)
> >
> >
> > Get the name you always wanted with the new y7mail email address.
> > www.yahoo7.com.au/y7mail
> >
> >
> > Get the name you always wanted with the new y7mail email address.
> > www.yahoo7.com.au/y7mail
> >
> >
>
