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https://issues.apache.org/jira/browse/HDFS-3222?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13249800#comment-13249800
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Uma Maheswara Rao G commented on HDFS-3222:
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@Todd,
I think our proposal won't work here, because by the time of hsync, DN will
not report to NN anyway. So, NN can not know the length and will persist that
length as 0 only. So, even if we retun block size when we find the locations 0,
will not help to solve the problem. am i missing?
I updated the patch for simulating the issue. Even if we fix in our proposed
way, test will fail.
So, we may have to think alternative approach for this issue.
> DFSInputStream#openInfo should not silently get the length as 0 when
> locations length is zero for last partial block.
> ---------------------------------------------------------------------------------------------------------------------
>
> Key: HDFS-3222
> URL: https://issues.apache.org/jira/browse/HDFS-3222
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: hdfs client
> Affects Versions: 1.0.3, 2.0.0, 3.0.0
> Reporter: Uma Maheswara Rao G
> Assignee: Uma Maheswara Rao G
> Attachments: HDFS-3222-Test.patch
>
>
> I have seen one situation with Hbase cluster.
> Scenario is as follows:
> 1)1.5 blocks has been written and synced.
> 2)Suddenly cluster has been restarted.
> Reader opened the file and trying to get the length., By this time partial
> block contained DNs are not reported to NN. So, locations for this partial
> block would be 0. In this case, DFSInputStream assumes that, 1 block size as
> final size.
> But reader also assuming that, 1 block size is the final length and setting
> his end marker. Finally reader ending up reading only partial data. Due to
> this, HMaster could not replay the complete edits.
> Actually this happend with 20 version. Looking at the code, same should
> present in trunk as well.
> {code}
> int replicaNotFoundCount = locatedblock.getLocations().length;
>
> for(DatanodeInfo datanode : locatedblock.getLocations()) {
> ..........
> ..........
> // Namenode told us about these locations, but none know about the replica
> // means that we hit the race between pipeline creation start and end.
> // we require all 3 because some other exception could have happened
> // on a DN that has it. we want to report that error
> if (replicaNotFoundCount == 0) {
> return 0;
> }
> {code}
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