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From AJ Chen <ajc...@web2express.org>
Subject Re: hadoop or nutch problem?
Date Sat, 02 Oct 2010 17:28:29 GMT
More observations: during hadoop job running, this "filesystem closed" error
happens consistently.
2010-10-02 05:29:58,951 WARN  mapred.TaskTracker - Error running child
java.io.IOException: Filesystem closed
        at org.apache.hadoop.hdfs.DFSClient.checkOpen(DFSClient.java:226)
        at org.apache.hadoop.hdfs.DFSClient.access$600(DFSClient.java:67)
        at
org.apache.hadoop.hdfs.DFSClient$DFSInputStream.close(DFSClient.java:1678)
        at java.io.FilterInputStream.close(FilterInputStream.java:155)
        at
org.apache.hadoop.io.SequenceFile$Reader.close(SequenceFile.java:1584)
        at
org.apache.hadoop.mapred.SequenceFileRecordReader.close(SequenceFileRecordReader.java:125)
        at
org.apache.hadoop.mapred.MapTask$TrackedRecordReader.close(MapTask.java:198)
        at org.apache.hadoop.mapred.MapTask.runOldMapper(MapTask.java:362)
        at org.apache.hadoop.mapred.MapTask.run(MapTask.java:307)
        at org.apache.hadoop.mapred.Child.main(Child.java:170)
2010-10-02 05:29:58,979 WARN  mapred.TaskRunner - Parent died.  Exiting
attempt_201009301134_0006_m_000074_1

Could this error turns on the safemode in hadoop? I suspect this because the
next hadoop job is supposed to create a segment directory and write out
segment results, but it does not create the directory.  Anything else could
happen to hdfs?

thanks,
-aj

On Tue, Sep 28, 2010 at 4:40 PM, AJ Chen <ajchen@web2express.org> wrote:

> I'm doing web crawling using nutch, which runs on hadoop in distributed
> mode. When the crawldb has tens of millions of urls, I have started to see
> strange failure in generating new segment and updating crawldb.
> For generating segment, the hadoop job for select is completed successfully
> and generate-temp-1285641291765 is created. but it does not start the
> partition job and the segment is not created in segments directory. I try to
> understand where it fails. There is no error message except for a few WARN
> messages about connection reset by peer. Hadoop fsck and dfsadmin show the
> nodes and directories are healthy. Is this a hadoop problem or nutch
> problem? I'll appreciate any suggestion for how to debug this fatal
> problem.
>
> Similar problem is seen for updatedb step, which creates the temp dir but
> never actually update the crawldb.
>
> thanks,
> aj
> --
> AJ Chen, PhD
> Chair, Semantic Web SIG, sdforum.org
> web2express.org
> twitter: @web2express
> Palo Alto, CA, USA
>

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