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https://issues.apache.org/jira/browse/HDFS-11708?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16024087#comment-16024087
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Brahma Reddy Battula commented on HDFS-11708:
---------------------------------------------
Yes, After HDFS-9807, patch will not apply cleanly. I missed this change.
*org.apache.hadoop.hdfs.TestPread#testPreadFailureWithChangedBlockLocations
{color:red}will fail without changes{color}.Following is stacktrace.*
{noformat}
org.apache.hadoop.hdfs.BlockMissingException: Could not obtain block:
BP-586358626-10.18.246.125-1495677968099:blk_1073741825_1001 file=/test
at
org.apache.hadoop.hdfs.DFSInputStream.chooseDataNode(DFSInputStream.java:843)
at
org.apache.hadoop.hdfs.DFSInputStream.fetchBlockByteRange(DFSInputStream.java:962)
at org.apache.hadoop.hdfs.DFSInputStream.pread(DFSInputStream.java:1324)
at org.apache.hadoop.hdfs.DFSInputStream.read(DFSInputStream.java:1283)
at
org.apache.hadoop.hdfs.TestPread.doPreadTestWithChangedLocations(TestPread.java:684)
at
org.apache.hadoop.hdfs.TestPread.testPreadFailureWithChangedBlockLocations(TestPread.java:566)
{noformat}
*org.apache.hadoop.hdfs.TestPread#testPreadHedgedFailureWithChangedBlockLocations*
hedged read would pass even without these changes because there is ignoredNodes
map always maintained without clearing, so there was a chance to connect to
valid node and read the replica.and this addressed in HDFS-11738
[~vinayrpet] already mentioned about this.
can we add HDFS-11738 changes here only Or can you move hedgedread changes to
HDFS-11738 itself..?
> positional read will fail if replicas moved to different DNs after stream is
> opened
> -----------------------------------------------------------------------------------
>
> Key: HDFS-11708
> URL: https://issues.apache.org/jira/browse/HDFS-11708
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: hdfs-client
> Affects Versions: 2.7.3
> Reporter: Vinayakumar B
> Assignee: Vinayakumar B
> Priority: Critical
> Labels: release-blocker
> Attachments: HDFS-11708-01.patch, HDFS-11708-02.patch,
> HDFS-11708-03.patch, HDFS-11708-04.patch
>
>
> Scenario:
> 1. File was written to DN1, DN2 with RF=2
> 2. File stream opened to read and kept. Block Locations are [DN1,DN2]
> 3. One of the replica (DN2) moved to another datanode (DN3) due to datanode
> dead/balancing/etc.
> 4. Latest block locations in NameNode will be DN1 and DN3 in the 'same order'
> 5. DN1 went down, but not yet detected as dead in NameNode.
> 6. Client start reading using positional read api "read(pos, buf[], offset,
> length)"
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