[jira] [Commented] (LOG4J2-2903) Cannot log to HDFS with a custom appender?

["Volkan Yazici (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/LOG4J2-2903?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17470574#comment-17470574 ] 

Volkan Yazici commented on LOG4J2-2903:
---------------------------------------

Hello [~TheDevManager], a skimmed through the sources, and below are my findings:

* Mind providing a minimal self-sufficient (preferably Maven) project reproducing the issue, please?
* I see that {{HDFSAppender}} extend from {{org.apache.log4j.AppenderSkeleton}}, which has the following Javadoc: _"The base class for Appenders in Log4j 1. Appenders constructed using this are ignored in Log4j 2."_ Mind using {{org.apache.logging.log4j.core.appender.AbstractAppender}} instead?

> Cannot log to HDFS with a custom appender?
> ------------------------------------------
>
>                 Key: LOG4J2-2903
>                 URL: https://issues.apache.org/jira/browse/LOG4J2-2903
>             Project: Log4j 2
>          Issue Type: Bug
>          Components: Appenders, JMX, Scala API
>    Affects Versions: 2.12.1
>         Environment: Spark 2.4.6, Scala 2.1.2, Hadoop 3.2.1
> Unit tests: Windows 10, maven Eclipse 4.7 (Scala IDE) Junit 4
> Runtime tests:   Ubuntu 16.04,18.04, (test/staging), Spark cluster, HDFS cluster
>            Reporter: Thomas Humphries
>            Priority: Minor
>         Attachments: HDFSAppender.scala, LoggingTest.scala, MavenDependencies.txt, log4j.properties
>
>
> *Overview*
>  [(x-post from public StackOverflow question)|https://stackoverflow.com/questions/63276838/scala-how-to-create-logs-on-hdfs-with-a-log4j-custom-appender]
> We want to log our Spark job activity using log4j to write log files to HDFS.
>  - Java 8, Spark 2.4.6, Scala 2.1.2, Hadoop 3.2.1
> We were Unable to find a native apache log4j appenders to write to HDFS (Apache Flume in not an option), so set out to write our own.
> We constructed a simple custom log4j appender  (Spark-submit with our java.jar writes to HDFS).
> *does not work*
> Scala logic matched Java; however, logging to HDFS fails consistently with a Stack overflow or OOM error.
> We cannot find anything obviously wrong?
> *The implementation:*
> Here is a simple hello-world project to reproduce the issue:
>  - Scala project (Maven build), containing a simple main class, and:
>  - HDFSAppender class (extends log4j AppenderSkeleton)
>  - LoggingTest unit test class
>  - log4j configuration file for testing
> **The error**
> Any logging event causes the program to crash with a stack overflow error:
> {code:bash}
>    java.util.concurrent.ExecutionException: java.lang.StackOverflowError
> 	at java.util.concurrent.FutureTask.report(FutureTask.java:122)
> 	at java.util.concurrent.FutureTask.get(FutureTask.java:206)
> 	at org.apache.hadoop.util.ShutdownHookManager.executeShutdown(ShutdownHookManager.java:124)
> 	at org.apache.hadoop.util.ShutdownHookManager$1.run(ShutdownHookManager.java:95)
> Caused by: java.lang.StackOverflowError
> 	at org.apache.log4j.PatternLayout.format(PatternLayout.java:506)
> 	at org.apache.log4j.WriterAppender.subAppend(WriterAppender.java:310)
> 	at org.apache.log4j.WriterAppender.append(WriterAppender.java:162)
> {code}
> Then the following messages appear, implying some kind of loop/race condition:
> {code:bash}
> at org.apache.log4j.AppenderSkeleton.doAppend(AppenderSkeleton.java:251)
> 	at org.apache.log4j.helpers.AppenderAttachableImpl.appendLoopOnAppenders(AppenderAttachableImpl.java:66)
> 	at org.apache.log4j.Category.callAppenders(Category.java:206)
> 	at org.apache.log4j.Category.forcedLog(Category.java:391)
> 	at org.apache.log4j.Category.log(Category.java:856)
> 	at org.slf4j.impl.Log4jLoggerAdapter.warn(Log4jLoggerAdapter.java:401)
> 	at org.apache.spark.internal.Logging.logWarning(Logging.scala:66)
> 	at org.apache.spark.internal.Logging.logWarning$(Logging.scala:65)
> 	at org.apache.spark.SparkContext$.logWarning(SparkContext.scala:2442)
> 	at org.apache.spark.SparkContext$.$anonfun$assertNoOtherContextIsRunning$5(SparkContext.scala:2500)
> 	at org.apache.spark.SparkContext$.$anonfun$assertNoOtherContextIsRunning$5$adapted(SparkContext.scala:2491)
> 	at scala.Option.foreach(Option.scala:274)
> 	at org.apache.spark.SparkContext$.assertNoOtherContextIsRunning(SparkContext.scala:2491)
> 	at org.apache.spark.SparkContext$.markPartiallyConstructed(SparkContext.scala:2568)
> 	at org.apache.spark.SparkContext.<init>(SparkContext.scala:85)
> 	at org.apache.spark.SparkContext$.getOrCreate(SparkContext.scala:2520)
> 	at org.apache.spark.sql.SparkSession$Builder.$anonfun$getOrCreate$5(SparkSession.scala:935)
> 	at scala.Option.getOrElse(Option.scala:138)
> 	at org.apache.spark.sql.SparkSession$Builder.getOrCreate(SparkSession.scala:926)
> 	at com.obfuscated.test.spark.log4j.HDFSLogWriter.write(HDFSLogWriter.scala:23)
> 	at com.obfuscated.test.spark.log4j.HDFSAppender.append(HDFSAppender.scala:63)
> (repeats 48 times...)
> {code}



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