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Posted to issues@spark.apache.org by "Sean Owen (JIRA)" <ji...@apache.org> on 2015/07/25 12:59:04 UTC
[jira] [Commented] (SPARK-9339) Use of Class.forName(String) should
be replaced with version taking classloader
[ https://issues.apache.org/jira/browse/SPARK-9339?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14641537#comment-14641537 ]
Sean Owen commented on SPARK-9339:
----------------------------------
In fact, it is disallowed altogether now: https://issues.apache.org/jira/browse/SPARK-8962
> 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
> Reporter: Mridul Muralidharan
>
> 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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