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https://issues.apache.org/jira/browse/LOG4J2-2816?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17082666#comment-17082666
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Remko Popma commented on LOG4J2-2816:
-------------------------------------
Thank you for the info, that is helpful: I cannot find any problems with the
Log4j configuration.
Some more version questions: what version of the LMAX Disruptor are you using,
and what operating system and version?
I don't have a clear "smoking gun" candidate that I suspect could be the cause
of this.
The "purging class loader data graph" log is emitted by
[SafepointSynchronize::do_cleanup_tasks|http://hg.openjdk.java.net/jdk8u/jdk8u-dev/hotspot/file/7384f6a12fc1/src/share/vm/runtime/safepoint.cpp#l544],
so there seems to be some correlation between a safepoint being reached - and
potentially a garbage collection taking place - and this NPE. What GC algorithm
are you using?
Depending on what version of LMAX Disruptor you are currently on, you could try
upgrading to [3.4.2|https://github.com/LMAX-Exchange/disruptor].
Alternatively, you can try reverting to a previous version of Log4j to see if
the problem still occurs.
Specifically, there was some Async Logging work done in Log4j
[2.12.0|http://logging.apache.org/log4j/2.x/changes-report.html#a2.12.0] that
touched this area of the code, you could try if the problem still occurs with a
version prior to that, for example, you could try with Log4j version 2.11.2.
> NullPointerException from AsyncLogger
> -------------------------------------
>
> Key: LOG4J2-2816
> URL: https://issues.apache.org/jira/browse/LOG4J2-2816
> Project: Log4j 2
> Issue Type: Bug
> Components: Core
> Affects Versions: 2.13.0
> Reporter: Denis
> Priority: Minor
>
> We've got several times following NullPointerException (example from our
> stdout.log):
>
> {code:java}
> 84449.232: [purging class loader data graph, 0.0000003 secs]
> AsyncLogger error handling event seq=1037012,
> value='org.apache.logging.log4j.core.async.RingBufferLogEvent@2a7b2d78':
> java.lang.NullPointerException: null
> java.lang.NullPointerException
> at
> org.apache.logging.log4j.core.async.RingBufferLogEvent.execute(RingBufferLogEvent.java:161)
> at
> org.apache.logging.log4j.core.async.RingBufferLogEventHandler.onEvent(RingBufferLogEventHandler.java:46)
> at
> org.apache.logging.log4j.core.async.RingBufferLogEventHandler.onEvent(RingBufferLogEventHandler.java:29)
> at
> com.lmax.disruptor.BatchEventProcessor.processEvents(BatchEventProcessor.java:168)
> at com.lmax.disruptor.BatchEventProcessor.run(BatchEventProcessor.java:125)
> at java.lang.Thread.run(Thread.java:748)
> AsyncLogger error handling event seq=1037022,
> value='org.apache.logging.log4j.core.async.RingBufferLogEvent@d5d330f':
> java.lang.NullPointerException: null
> java.lang.NullPointerException
> at
> org.apache.logging.log4j.core.async.RingBufferLogEvent.execute(RingBufferLogEvent.java:161)
> at
> org.apache.logging.log4j.core.async.RingBufferLogEventHandler.onEvent(RingBufferLogEventHandler.java:46)
> at
> org.apache.logging.log4j.core.async.RingBufferLogEventHandler.onEvent(RingBufferLogEventHandler.java:29)
> at
> com.lmax.disruptor.BatchEventProcessor.processEvents(BatchEventProcessor.java:168)
> at com.lmax.disruptor.BatchEventProcessor.run(BatchEventProcessor.java:125)
> at java.lang.Thread.run(Thread.java:748)
> 84450.232: [deflating idle monitors, 0.0000624 secs]
> {code}
>
> What is interesting this NPEs always preceeded by
> {code}
> 84449.232: [purging class loader data graph, 0.0000003 secs] vm message
> {code}
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