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From "Hadoop QA (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HDFS-127) DFSClient block read failures cause open DFSInputStream to become unusable
Date Tue, 20 Oct 2009 05:40:59 GMT

    [ https://issues.apache.org/jira/browse/HDFS-127?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12767701#action_12767701
] 

Hadoop QA commented on HDFS-127:
--------------------------------

-1 overall.  Here are the results of testing the latest attachment 
  http://issues.apache.org/jira/secure/attachment/12422638/h127_20091019b.patch
  against trunk revision 826905.

    +1 @author.  The patch does not contain any @author tags.

    -1 tests included.  The patch doesn't appear to include any new or modified tests.
                        Please justify why no new tests are needed for this patch.
                        Also please list what manual steps were performed to verify this patch.

    +1 javadoc.  The javadoc tool did not generate any warning messages.

    +1 javac.  The applied patch does not increase the total number of javac compiler warnings.

    +1 findbugs.  The patch does not introduce any new Findbugs warnings.

    +1 release audit.  The applied patch does not increase the total number of release audit
warnings.

    -1 core tests.  The patch failed core unit tests.

    +1 contrib tests.  The patch passed contrib unit tests.

Test results: http://hudson.zones.apache.org/hudson/job/Hdfs-Patch-h2.grid.sp2.yahoo.net/41/testReport/
Findbugs warnings: http://hudson.zones.apache.org/hudson/job/Hdfs-Patch-h2.grid.sp2.yahoo.net/41/artifact/trunk/build/test/findbugs/newPatchFindbugsWarnings.html
Checkstyle results: http://hudson.zones.apache.org/hudson/job/Hdfs-Patch-h2.grid.sp2.yahoo.net/41/artifact/trunk/build/test/checkstyle-errors.html
Console output: http://hudson.zones.apache.org/hudson/job/Hdfs-Patch-h2.grid.sp2.yahoo.net/41/console

This message is automatically generated.

> DFSClient block read failures cause open DFSInputStream to become unusable
> --------------------------------------------------------------------------
>
>                 Key: HDFS-127
>                 URL: https://issues.apache.org/jira/browse/HDFS-127
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: hdfs client
>            Reporter: Igor Bolotin
>            Assignee: Tsz Wo (Nicholas), SZE
>         Attachments: 4681.patch, h127_20091016.patch, h127_20091019.patch, h127_20091019b.patch
>
>
> We are using some Lucene indexes directly from HDFS and for quite long time we were using
Hadoop version 0.15.3.
> When tried to upgrade to Hadoop 0.19 - index searches started to fail with exceptions
like:
> 2008-11-13 16:50:20,314 WARN [Listener-4] [] DFSClient : DFS Read: java.io.IOException:
Could not obtain block: blk_5604690829708125511_15489 file=/usr/collarity/data/urls-new/part-00000/20081110-163426/_0.tis
> at org.apache.hadoop.hdfs.DFSClient$DFSInputStream.chooseDataNode(DFSClient.java:1708)
> at org.apache.hadoop.hdfs.DFSClient$DFSInputStream.blockSeekTo(DFSClient.java:1536)
> at org.apache.hadoop.hdfs.DFSClient$DFSInputStream.read(DFSClient.java:1663)
> at java.io.DataInputStream.read(DataInputStream.java:132)
> at org.apache.nutch.indexer.FsDirectory$DfsIndexInput.readInternal(FsDirectory.java:174)
> at org.apache.lucene.store.BufferedIndexInput.refill(BufferedIndexInput.java:152)
> at org.apache.lucene.store.BufferedIndexInput.readByte(BufferedIndexInput.java:38)
> at org.apache.lucene.store.IndexInput.readVInt(IndexInput.java:76)
> at org.apache.lucene.index.TermBuffer.read(TermBuffer.java:63)
> at org.apache.lucene.index.SegmentTermEnum.next(SegmentTermEnum.java:131)
> at org.apache.lucene.index.SegmentTermEnum.scanTo(SegmentTermEnum.java:162)
> at org.apache.lucene.index.TermInfosReader.scanEnum(TermInfosReader.java:223)
> at org.apache.lucene.index.TermInfosReader.get(TermInfosReader.java:217)
> at org.apache.lucene.index.SegmentTermDocs.seek(SegmentTermDocs.java:54) 
> ...
> The investigation showed that the root of this issue is that we exceeded # of xcievers
in the data nodes and that was fixed by changing configuration settings to 2k.
> However - one thing that bothered me was that even after datanodes recovered from overload
and most of client servers had been shut down - we still observed errors in the logs of running
servers.
> Further investigation showed that fix for HADOOP-1911 introduced another problem - the
DFSInputStream instance might become unusable once number of failures over lifetime of this
instance exceeds configured threshold.
> The fix for this specific issue seems to be trivial - just reset failure counter before
reading next block (patch will be attached shortly).
> This seems to be also related to HADOOP-3185, but I'm not sure I really understand necessity
of keeping track of failed block accesses in the DFS client.

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