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https://issues.apache.org/jira/browse/HDFS-12151?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16100787#comment-16100787
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Aaron Fabbri commented on HDFS-12151:
-------------------------------------
Looks straightforward. +1 (non-binding).
Confirmed by inspection that the null you may pass in is handled correctly in
{{Sender#writeBlock()}} via {{PBHelperClient.convert()}} which returns an empty
list.
For upstream regression testing, where would be a good place to add a test for
this? I don't think a test is a must-have for this small improvement, but it
does highlight our need for better compatibility testing here. Do we have an
upstream HDFS protocol compatibility testing JIRA we could add this case to?
> Hadoop 2 clients cannot writeBlock to Hadoop 3 DataNodes
> --------------------------------------------------------
>
> Key: HDFS-12151
> URL: https://issues.apache.org/jira/browse/HDFS-12151
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: rolling upgrades
> Affects Versions: 3.0.0-alpha4
> Reporter: Sean Mackrory
> Assignee: Sean Mackrory
> Attachments: HDFS-12151.001.patch
>
>
> Trying to write to a Hadoop 3 DataNode with a Hadoop 2 client currently
> fails. On the client side it looks like this:
> {code}
> 17/07/14 13:31:58 INFO hdfs.DFSClient: Exception in
> createBlockOutputStream
> java.io.EOFException: Premature EOF: no length prefix available
> at
> org.apache.hadoop.hdfs.protocolPB.PBHelper.vintPrefixed(PBHelper.java:2280)
> at
> org.apache.hadoop.hdfs.DFSOutputStream$DataStreamer.createBlockOutputStream(DFSOutputStream.java:1318)
> at
> org.apache.hadoop.hdfs.DFSOutputStream$DataStreamer.nextBlockOutputStream(DFSOutputStream.java:1237)
> at
> org.apache.hadoop.hdfs.DFSOutputStream$DataStreamer.run(DFSOutputStream.java:449){code}
> But on the DataNode side there's an ArrayOutOfBoundsException because there
> aren't any targetStorageIds:
> {code}
> java.lang.ArrayIndexOutOfBoundsException: 0
> at
> org.apache.hadoop.hdfs.server.datanode.DataXceiver.writeBlock(DataXceiver.java:815)
> at
> org.apache.hadoop.hdfs.protocol.datatransfer.Receiver.opWriteBlock(Receiver.java:173)
> at
> org.apache.hadoop.hdfs.protocol.datatransfer.Receiver.processOp(Receiver.java:107)
> at
> org.apache.hadoop.hdfs.server.datanode.DataXceiver.run(DataXceiver.java:290)
> at java.lang.Thread.run(Thread.java:745){code}
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