[SPARK-9339] Use of Class.forName(String) should be replaced with version taking classloader

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Duplicate
• Affects Version/s: 1.3.1
• Assignee: Unassigned
• Reporter: Mridul Muralidharan
• Created: 25/Jul/15 10:50
• Updated: 02/Feb/16 16:41
• Resolved: 27/Jul/15 07:49

Description

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.

Issue Links

• duplicates: SPARK-8962 Disallow Class.forName