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https://issues.apache.org/jira/browse/NUTCH-2551?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16433705#comment-16433705
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Omkar Reddy commented on NUTCH-2551:
------------------------------------

[~wastl-nagel], [~HansBrende], [~lewi...@apache.org] please let me know your 
thoughts on my explanation above so that I can send a PR with the fix. Thanks. 

> NullPointerException in generator
> ---------------------------------
>
>                 Key: NUTCH-2551
>                 URL: https://issues.apache.org/jira/browse/NUTCH-2551
>             Project: Nutch
>          Issue Type: Bug
>          Components: generator
>    Affects Versions: 1.15
>            Reporter: Hans Brende
>            Priority: Blocker
>             Fix For: 1.15
>
>
> A NullPointerException is thrown during the crawl generate stage when I 
> deploy to a hadoop cluster (but for some reason, it works fine locally).
> It looks like this is caused because the URLPartitioner class still has the 
> old {{configure()}} method in there (which is never called, causing the 
> {{normalizers}} field to remain null), rather than implementing the 
> {{Configurable}} interface as detailed in the newer mapreduce API's 
> Partitioner spec.
> Stack trace:
> {code}
> java.lang.NullPointerException
>  at org.apache.nutch.crawl.URLPartitioner.getPartition(URLPartitioner.java:76)
>  at org.apache.nutch.crawl.URLPartitioner.getPartition(URLPartitioner.java:40)
>  at 
> org.apache.hadoop.mapred.MapTask$NewOutputCollector.write(MapTask.java:716)
>  at 
> org.apache.hadoop.mapreduce.task.TaskInputOutputContextImpl.write(TaskInputOutputContextImpl.java:89)
>  at 
> org.apache.hadoop.mapreduce.lib.map.WrappedMapper$Context.write(WrappedMapper.java:112)
>  at 
> org.apache.nutch.crawl.Generator$SelectorInverseMapper.map(Generator.java:553)
>  at 
> org.apache.nutch.crawl.Generator$SelectorInverseMapper.map(Generator.java:546)
>  at org.apache.hadoop.mapreduce.Mapper.run(Mapper.java:146)
>  at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:787)
>  at org.apache.hadoop.mapred.MapTask.run(MapTask.java:341)
>  at org.apache.hadoop.mapred.YarnChild$2.run(YarnChild.java:175)
>  at java.security.AccessController.doPrivileged(Native Method)
>  at javax.security.auth.Subject.doAs(Subject.java:422)
>  at 
> org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1836)
>  at org.apache.hadoop.mapred.YarnChild.main(YarnChild.java:169)
> {code}
>  
> Oh and it might also be because a *static* URLPartitioner instance is being 
> used in the Generator.Selector class... but it's only initialized in the 
> {{setup()}} method of the Generator.Selector.SelectorMapper class! So that 
> whole setup looks pretty weird...



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