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https://issues.apache.org/jira/browse/NUTCH-1084?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13104103#comment-13104103
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Steven Bedrick commented on NUTCH-1084:
---------------------------------------
Oddly enough, I'm seeing exactly the same thing. I'm still getting the hang of
Nutch, and so am writing a little tool to dump the contents of a crawldb
(similar to the built-in readdb command) as a way to become familiar with some
of the Nutch classes. In my case, all I'm doing is iterating over the crawldb
MapFile, and just printing keys and values. It works just fine until it gets to
the first CrawlDatum that has metadata, at which point it chokes and dies with
an identical stack trace. Interestingly, just running "bin/nutch readdb ...
-dump ..." works flawlessly.
> ReadDB url throws exception
> ---------------------------
>
> Key: NUTCH-1084
> URL: https://issues.apache.org/jira/browse/NUTCH-1084
> Project: Nutch
> Issue Type: Bug
> Affects Versions: 1.4
> Reporter: Markus Jelsma
> Fix For: 1.4
>
>
> Readdb -url suffers from two problems:
> 1. it trips over the _SUCCESS file generated by newer Hadoop version
> 2. throws can't find class: org.apache.nutch.protocol.ProtocolStatus (???)
> The first problem can be remedied by not allowing the injector or updater to
> write the _SUCCESS file. Until now that's the solution implemented for
> similar issues. I've not been successful as to make the Hadoop readers simply
> skip the file.
> The second issue seems a bit strange and did not happen on a local check out.
> I'm not yet sure whether this is a Hadoop issue or something being corrupt in
> the CrawlDB. Here's the stack trace:
> {code}
> Exception in thread "main" java.io.IOException: can't find class:
> org.apache.nutch.protocol.ProtocolStatus because
> org.apache.nutch.protocol.ProtocolStatus
> at
> org.apache.hadoop.io.AbstractMapWritable.readFields(AbstractMapWritable.java:204)
> at org.apache.hadoop.io.MapWritable.readFields(MapWritable.java:146)
> at org.apache.nutch.crawl.CrawlDatum.readFields(CrawlDatum.java:278)
> at
> org.apache.hadoop.io.SequenceFile$Reader.getCurrentValue(SequenceFile.java:1751)
> at org.apache.hadoop.io.MapFile$Reader.get(MapFile.java:524)
> at
> org.apache.hadoop.mapred.MapFileOutputFormat.getEntry(MapFileOutputFormat.java:105)
> at org.apache.nutch.crawl.CrawlDbReader.get(CrawlDbReader.java:383)
> at
> org.apache.nutch.crawl.CrawlDbReader.readUrl(CrawlDbReader.java:389)
> at org.apache.nutch.crawl.CrawlDbReader.main(CrawlDbReader.java:514)
> at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
> at
> sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
> at
> sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
> at java.lang.reflect.Method.invoke(Method.java:597)
> at org.apache.hadoop.util.RunJar.main(RunJar.java:156)
> {code}
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