The first thing that I wanted to look at is why 2.13.2 is not being used. We
are using apache-storm, through which our project has the maven dependency
storm-core with a provided scope. Storm-core has dependencies on log4j-api,
log4j-core, and log4j-slf4j-impl. It seems like these have provided scope as
well, since explicitly declaring a dependency on these log4j dependencies does
not result in the version being different than the transitive version included
with storm-core (which is 2.8.2, not 2.13.2). Not sure if this is the right
place for this issue
From: log4j-user@logging.apache.org At: 05/23/20 20:27:18To: Mitchell Rathbun
(BLOOMBERG/ 731 LEX ) , log4j-user@logging.apache.org
Subject: Re: ConcurrentModificationException when using AsyncLogger
This stack trace is not from Log4j 2.13.2. The line numbers don’t match. This
error indicates that one of the parameters being passed on the logging method
is a Collection. The Layout is iterating over the Collection in an attempt to
format it. However, some other thread is modifying the Collection while the
Async Logger thread is trying to iterate through it. Log4j has no way to
prevent this as it is an object owned by the application.
1. See above.
2. It would be expected that the stack trace would be coming from the
StatusLogger, which appears to be the case. I don’t see any reason logging
would continue to fail. The AppenderControl should catch the error. However, if
you have configured the Appender to not ignore exceptions then it is possible
that that AsyncLoggerConfig is not handling the error. We will have to look
further to see if that is the case.
Ralph
> On May 23, 2020, at 3:46 PM, Mitchell Rathbun (BLOOMBERG/ 731 LEX)
<mrathb...@bloomberg.net> wrote:
>
> We recently started occasionally getting the following error:
>
> 2020-05-22 05:54:07,995 INFO STDERR [Thread-2] {} 2020-05-22 05:54:07,994
Log4j2-TF-2-AsyncLoggerConfig-1 ERROR An exception occurred processing Appender
WINGMAN java.util.ConcurrentModificationException
> 2020-05-22 05:54:07,996 INFO STDERR [Thread-2] {} at
java.util.HashMap$HashIterator.nextNode(HashMap.java:1442)
> 2020-05-22 05:54:07,996 INFO STDERR [Thread-2] {} at
java.util.HashMap$KeyIterator.next(HashMap.java:1466)
> 2020-05-22 05:54:07,996 INFO STDERR [Thread-2] {} at
org.apache.logging.log4j.message.ParameterFormatter.appendCollection(ParameterFo
rmatter.java:599)
> 2020-05-22 05:54:07,996 INFO STDERR [Thread-2] {} at
org.apache.logging.log4j.message.ParameterFormatter.appendPotentiallyRecursiveVa
lue(ParameterFormatter.java:507)
> 2020-05-22 05:54:07,996 INFO STDERR [Thread-2] {} at
org.apache.logging.log4j.message.ParameterFormatter.recursiveDeepToString(Parame
terFormatter.java:432)
> 2020-05-22 05:54:07,996 INFO STDERR [Thread-2] {} at
org.apache.logging.log4j.message.ParameterFormatter.formatMessage2(ParameterForm
atter.java:189)
> 2020-05-22 05:54:07,996 INFO STDERR [Thread-2] {} at
org.apache.logging.log4j.message.ParameterizedMessage.formatTo(ParameterizedMess
age.java:225)
> 2020-05-22 05:54:07,996 INFO STDERR [Thread-2] {} at
org.apache.logging.log4j.core.pattern.MessagePatternConverter.format(MessagePatt
ernConverter.java:119)
> 2020-05-22 05:54:07,996 INFO STDERR [Thread-2] {} at
org.apache.logging.log4j.core.pattern.PatternFormatter.format(PatternFormatter.j
ava:38)
> 2020-05-22 05:54:07,996 INFO STDERR [Thread-2] {} at
org.apache.logging.log4j.core.layout.PatternLayout$PatternSerializer.toSerializa
ble(PatternLayout.java:333)
> 2020-05-22 05:54:07,996 INFO STDERR [Thread-2] {} at
org.apache.logging.log4j.core.layout.PatternLayout.toText(PatternLayout.java:232
)
> 2020-05-22 05:54:07,996 INFO STDERR [Thread-2] {} at
org.apache.logging.log4j.core.layout.PatternLayout.encode(PatternLayout.java:217
)
> 2020-05-22 05:54:07,996 INFO STDERR [Thread-2] {} at
org.apache.logging.log4j.core.layout.PatternLayout.encode(PatternLayout.java:57)
> 2020-05-22 05:54:07,996 INFO STDERR [Thread-2] {} at
org.apache.logging.log4j.core.appender.AbstractOutputStreamAppender.directEncode
Event(AbstractOutputStreamAppender.java:177)
> 2020-05-22 05:54:07,996 INFO STDERR [Thread-2] {} at
org.apache.logging.log4j.core.appender.AbstractOutputStreamAppender.tryAppend(Ab
stractOutputStreamAppender.java:170)
> 2020-05-22 05:54:07,996 INFO STDERR [Thread-2] {} at
org.apache.logging.log4j.core.appender.AbstractOutputStreamAppender.append(Abstr
actOutputStreamAppender.java:161)
> 2020-05-22 05:54:07,996 INFO STDERR [Thread-2] {} at
org.apache.logging.log4j.core.appender.RollingRandomAccessFileAppender.append(Ro
llingRandomAccessFileAppender.java:218)
> 2020-05-22 05:54:07,996 INFO STDERR [Thread-2] {} at
org.apache.logging.log4j.core.config.AppenderControl.tryCallAppender(AppenderCon
trol.java:156)
> 2020-05-22 05:54:07,996 INFO STDERR [Thread-2] {} at
org.apache.logging.log4j.core.config.AppenderControl.callAppender0(AppenderContr
ol.java:129)
> 2020-05-22 05:54:07,996 INFO STDERR [Thread-2] {} at
org.apache.logging.log4j.core.config.AppenderControl.callAppenderPreventRecursio
n(AppenderControl.java:120)
> 2020-05-22 05:54:07,996 INFO STDERR [Thread-2] {} at
org.apache.logging.log4j.core.config.AppenderControl.callAppender(AppenderContro
l.java:84)
> 2020-05-22 05:54:07,996 INFO STDERR [Thread-2] {} at
org.apache.logging.log4j.core.config.LoggerConfig.callAppenders(LoggerConfig.jav
a:448)
> 2020-05-22 05:54:07,996 INFO STDERR [Thread-2] {} at
org.apache.logging.log4j.core.async.AsyncLoggerConfig.asyncCallAppenders(AsyncLo
ggerConfig.java:115)
> 2020-05-22 05:54:07,996 INFO STDERR [Thread-2] {} at
org.apache.logging.log4j.core.async.AsyncLoggerConfigDisruptor$Log4jEventWrapper
Handler.onEvent(AsyncLoggerConfigDisruptor.java:112)
> 2020-05-22 05:54:07,996 INFO STDERR [Thread-2] {} at
org.apache.logging.log4j.core.async.AsyncLoggerConfigDisruptor$Log4jEventWrapper
Handler.onEvent(AsyncLoggerConfigDisruptor.java:98)
> 2020-05-22 05:54:07,996 INFO STDERR [Thread-2] {} at
com.lmax.disruptor.BatchEventProcessor.processEvents(BatchEventProcessor.java:16
9)
> 2020-05-22 05:54:07,996 INFO STDERR [Thread-2] {} at
com.lmax.disruptor.BatchEventProcessor.run(BatchEventProcessor.java:126)
> 2020-05-22 05:54:07,996 INFO STDERR [Thread-2] {} at
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
> 2020-05-22 05:54:07,996 INFO STDERR [Thread-2] {} at
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
> 2020-05-22 05:54:07,996 INFO STDERR [Thread-2] {} at
java.lang.Thread.run(Thread.java:748)
> 2020-05-22 05:54:07,996 INFO STDERR [Thread-2] {}
>
> We are using a RollingRandomAccessFileAppeneder with an AsyncLogger, and
recently upgraded our log4j2 version to 2.13.2. The system property
Log4jContextSelector is set to
org.apache.logging.log4j.core.selector.BasicContextSelector. It seems from the
few posts I have seen online that this shouldn't happen if async logging is
being used. So I have two questions:
>
> 1. Why are we seeing this/what generally could cause this?
>
> 2. When this error occurs, the file that logs were being written to gets
overwritten completely with the stack trace posted above. The process continues
to run after this but no new logs ever get written to the file. This makes this
a critical error and also makes it very difficult to debug why this error is
happening to begin with. Is there a way to prevent this from happening so that
the error just gets appended to the file instead of overwriting everything that
is there?
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