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From "Jingkei Ly (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-4975) CompositeRecordReader: ClassLoader set in JobConf is not passed onto WrappedRecordReaders
Date Fri, 02 Jan 2009 12:49:44 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-4975?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12660310#action_12660310
] 

Jingkei Ly commented on HADOOP-4975:
------------------------------------

I believe the test above fails because in Parser.java [line: 313] calls Parser.getConf() to
create a copy of the JobConf. Parser.getConf() which in turn uses the JobConf(JobConf) [JobConf.java
line:138] constructor to create a copied instance. I think problem is that that particular
JobConf constructor doesn't copy the reference to the classLoader to the new JobConf instance.

Should the JobConf/Configuration constructor copy the classLoader reference, or should it
be set in Parser.getConf()?

> CompositeRecordReader: ClassLoader set in JobConf is not passed onto WrappedRecordReaders
> -----------------------------------------------------------------------------------------
>
>                 Key: HADOOP-4975
>                 URL: https://issues.apache.org/jira/browse/HADOOP-4975
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: mapred
>    Affects Versions: 0.19.0
>            Reporter: Jingkei Ly
>         Attachments: break-wrapped-rr-test.patch
>
>
> 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:
> {code}
> 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
> {code}
> I'll attach a unit test that can demonstrate this more clearly....

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