Nutch 2, Solr 5 - solrdedup causes ClassCastException:

[Tom Chiverton]

I've tried using both Solr 6 and 5 with the latest Nutch 2, and with 
both I am getting an error from Nutch's bin/crawl.

mnt/nutch/nutch/runtime/local/bin/nutch solrdedup -D 
mapred.reduce.tasks=2 -D mapred.child.java.opts=-Xmx1000m -D 
mapred.reduce.tasks.speculative.execution=false -D 
mapred.map.tasks.speculative.execution=false -D 
mapred.compress.map.output=true http://localhost:8983/solr/nutch
Exception in thread "main" java.lang.RuntimeException: job failed: 
name=apache-nutch-2.3.1.jar, jobid=job_local2123017879_0001
        at 
org.apache.nutch.util.NutchJob.waitForCompletion(NutchJob.java:120)
        at 
org.apache.nutch.indexer.solr.SolrDeleteDuplicates.dedup(SolrDeleteDuplicates.java:383)
        at 
org.apache.nutch.indexer.solr.SolrDeleteDuplicates.run(SolrDeleteDuplicates.java:393)
        at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:70)
        at 
org.apache.nutch.indexer.solr.SolrDeleteDuplicates.main(SolrDeleteDuplicates.java:403)
Error running:
  /mnt/nutch/nutch/runtime/local/bin/nutch solrdedup -D 
mapred.reduce.tasks=2 -D mapred.child.java.opts=-Xmx1000m -D 
mapred.reduce.tasks.speculative.execution=false -D 
mapred.map.tasks.speculative.execution=false -D 
mapred.compress.map.output=true http://localhost:8983/solr/nutch
Failed with exit value 1.
hadoop.log says

java.lang.Exception: java.lang.ClassCastException: java.util.ArrayList 
cannot be cast to java.lang.String
        at 
org.apache.hadoop.mapred.LocalJobRunner$Job.runTasks(LocalJobRunner.java:462)
        at 
org.apache.hadoop.mapred.LocalJobRunner$Job.run(LocalJobRunner.java:522)
Caused by: java.lang.ClassCastException: java.util.ArrayList cannot be 
cast to java.lang.String
        at 
org.apache.nutch.indexer.solr.SolrDeleteDuplicates$SolrRecordReader.nextKeyValue(SolrDeleteDuplicates.java:233)
        at 
org.apache.hadoop.mapred.MapTask$NewTrackingRecordReader.nextKeyValue(MapTask.java:533)
        at 
org.apache.hadoop.mapreduce.task.MapContextImpl.nextKeyValue(MapContextImpl.java:80)
        at 
org.apache.hadoop.mapreduce.lib.map.WrappedMapper$Context.nextKeyValue(WrappedMapper.java:91)
        at org.apache.hadoop.mapreduce.Mapper.run(Mapper.java:144)
        at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:764)
        at org.apache.hadoop.mapred.MapTask.run(MapTask.java:340)
        at 
org.apache.hadoop.mapred.LocalJobRunner$Job$MapTaskRunnable.run(LocalJobRunner.java:243)
        at 
java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
        at java.util.concurrent.FutureTask.run(FutureTask.java:266)
        at 
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
        at 
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
        at java.lang.Thread.run(Thread.java:745)

Which appears to be related to the digest field somehow...

Is this a known bug ? Do I need a particular version of Nutch with a 
particular Solr or something ?
--
*Tom Chiverton*
Lead Developer
e:      t...@extravision.com <mailto:t...@extravision.com>
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