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https://issues.apache.org/jira/browse/NUTCH-2551?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16435271#comment-16435271
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Sebastian Nagel commented on NUTCH-2551:
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I was able to reproduce the problem in pseudo-distributed mode (Hadoop 2.8.3 on
Ubuntu 16.04) by running generate from a CrawlDb containing 100k URLs (from
diverse hosts). [~HansBrende]: I'll verify your solution. [~omkar20895]: which
Hadoop version did you test? I'll also share my setup scripts resp. will update
[NutchHadoopSingleNodeTutorial|https://wiki.apache.org/nutch/NutchHadoopSingleNodeTutorial].
> 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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