[HADOOP-4975] CompositeRecordReader: ClassLoader set in JobConf is not passed onto WrappedRecordReaders

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.19.0
• Fix Version/s: 0.21.0
• Hadoop Flags: Reviewed
• Assignee: Jingkei Ly
• Reporter: Jingkei Ly
• Created: 02/Jan/09 12:13
• Updated: 24/Aug/10 20:34
• Resolved: 23/Jan/09 22:35

Description

I am using a custom ClassLoader which I set in my JobConf via setClassLoader(). The ClassLoader is loaded key and value classes which are required to read records from SequenceFiles that were written out in a previous MapReduce job.

However, I am getting a ClassNotFoundException when using the CompositeInputFormat to create a RecordReader to read these SequenceFiles from HDFS. It occurs when the SequenceFile.Reader tries to create an instance of the Key/Value classes, presumably because the class loader SequenceFile.Reader is using is not the one I set with JobConf.setClassLoader. Below is an example of the stack trace I get:

Caused by: java.io.IOException: WritableName can't load class
	at org.apache.hadoop.io.WritableName.getClass(WritableName.java:73)
	at org.apache.hadoop.io.SequenceFile$Reader.getKeyClass(SequenceFile.java:1596)
	... 33 more
Caused by: java.lang.ClassNotFoundException: org.apache.hadoop.MyWritableClass
	at java.net.URLClassLoader$1.run(URLClassLoader.java:200)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:252)
	at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320)
	at java.lang.Class.forName0(Native Method)
	at java.lang.Class.forName(Class.java:247)
	at org.apache.hadoop.conf.Configuration.getClassByName(Configuration.java:673)
	at org.apache.hadoop.io.WritableName.getClass(WritableName.java:71)
	... 34 more

I'll attach a unit test that can demonstrate this more clearly....

Issue Links

• relates to: HADOOP-6103 Configuration clone constructor does not clone all the members.