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https://issues.apache.org/jira/browse/HDFS-127?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Tsz Wo (Nicholas), SZE updated HDFS-127:
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Component/s: hdfs client
> ... Any reason for making the bestNode static? You've changed what bestNode
> returns. It now returns null rather than throw an IOE with "no live nodes
> contain current block". Us over in hbase are not going to miss that message.
It is because bestNode(..) is a simple utility method. It does not use any
DFSClient fields/methods.
In the original codes, bestNode(..) is invoked only in chooseDataNode(..),
which basically use a try-catch to deal with the IOException thrown by
bestNode(..).
{code}
//original codes in chooseDataNode(..)
try {
DatanodeInfo chosenNode = bestNode(nodes, deadNodes);
...
} catch (IOException ie) {
...
LOG.info("Could not obtain block " + block.getBlock()
+ " from any node: " + ie
+ ". Will get new block locations from namenode and retry...");
...
}
{code}
As shown above, the IOException ie is used only for a log message. I think "No
live nodes contain current block" is a kind of redundant in the log message.
Do you think that "Could not obtain block " + block.getBlock() + " from any
node" is clear enough? No? We may change the log message if necessary.
> 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
> Attachments: 4681.patch, h127_20091016.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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