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From Marco Zanghì (JIRA) <j...@apache.org>
Subject [jira] [Updated] (SPARK-9339) Use of Class.forName(String) should be replaced with version taking classloader
Date Tue, 02 Feb 2016 16:37:39 GMT

     [ https://issues.apache.org/jira/browse/SPARK-9339?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Marco Zanghì updated SPARK-9339:
--------------------------------
    Attachment: screenshot-1yarn-cluster error.png

> Use of Class.forName(String) should be replaced with version taking classloader
> -------------------------------------------------------------------------------
>
>                 Key: SPARK-9339
>                 URL: https://issues.apache.org/jira/browse/SPARK-9339
>             Project: Spark
>          Issue Type: Bug
>    Affects Versions: 1.3.1
>            Reporter: Mridul Muralidharan
>         Attachments: screenshot-1yarn-cluster error.png
>
>
> In spark, multiple places have ability to take external class as input - example: listener.
> Other than in specific cases (like SparkEnv), the code typically calls Class.forName(clazzName)
> This works when the class is from within spark - but when the referenced class is from
external jar (user provided), it tends to fail.
> For example, in 1.3 we get this when using custom listener:
> ERROR ApplicationMaster: User class threw exception: Exception when registering SparkListener
> org.apache.spark.SparkException: Exception when registering SparkListener
> 	at org.apache.spark.SparkContext.setupAndStartListenerBus(SparkContext.scala:1726)
> 	at org.apache.spark.SparkContext.<init>(SparkContext.scala:429)
> 	at org.apache.spark.SparkContext.<init>(SparkContext.scala:134)
> 	at com.yahoo.corp.yst.webmap.spark.PageRankDataGenerator$.main(PageRankDataGenerator.scala:170)
> 	at com.yahoo.corp.yst.webmap.spark.PageRankDataGenerator.main(PageRankDataGenerator.scala)
> 	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
> 	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
> 	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
> 	at java.lang.reflect.Method.invoke(Method.java:606)
> 	at org.apache.spark.deploy.yarn.ApplicationMaster$$anon$2.run(ApplicationMaster.scala:480)
> Caused by: java.lang.ClassNotFoundException: <MySparkListener>
> 	at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
> 	at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
> 	at java.security.AccessController.doPrivileged(Native Method)
> 	at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
> 	at java.lang.ClassLoader.loadClass(ClassLoader.java:425)
> 	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
> 	at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
> 	at java.lang.Class.forName0(Native Method)
> 	at java.lang.Class.forName(Class.java:190)
> 	at org.apache.spark.SparkContext$$anonfun$setupAndStartListenerBus$1.apply(SparkContext.scala:1694)
> 	at org.apache.spark.SparkContext$$anonfun$setupAndStartListenerBus$1.apply(SparkContext.scala:1691)
> 	at scala.collection.IndexedSeqOptimized$class.foreach(IndexedSeqOptimized.scala:33)
> 	at scala.collection.mutable.WrappedArray.foreach(WrappedArray.scala:34)
> 	at org.apache.spark.SparkContext.setupAndStartListenerBus(SparkContext.scala:1691)
> 	... 9 more
> Instead of
> "val listenerClass = Class.forName(className)" in SparkContext.setupAndStartListenerBus,
we should use 
> "val listenerClass = Class.forName(className, true, Thread.currentThread().getContextClassLoader)"
> Note - this is a common pattern in spark, and might be relevant elsewhere too.



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