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https://issues.apache.org/jira/browse/HDFS-7884?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14352591#comment-14352591
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Vinayakumar B commented on HDFS-7884:
-------------------------------------
I think, its just a race between client-read and delete of the block.
Safe option is to null-check and throw ReplicaNotFoundException
{code} // Obtain a reference before reading data
FsVolumeSpi volume = datanode.data.getVolume(block);
if (volume == null) {
// This is race b/n delete and read
throw new ReplicaNotFoundException(block);
}
this.volumeRef = volume.obtainReference();{code}
> NullPointerException in BlockSender
> -----------------------------------
>
> Key: HDFS-7884
> URL: https://issues.apache.org/jira/browse/HDFS-7884
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: datanode
> Reporter: Tsz Wo Nicholas Sze
> Assignee: Brahma Reddy Battula
> Priority: Blocker
> Attachments:
> org.apache.hadoop.hdfs.TestAppendSnapshotTruncate-output.txt
>
>
> {noformat}
> java.lang.NullPointerException
> at
> org.apache.hadoop.hdfs.server.datanode.BlockSender.<init>(BlockSender.java:264)
> at
> org.apache.hadoop.hdfs.server.datanode.DataXceiver.readBlock(DataXceiver.java:506)
> at
> org.apache.hadoop.hdfs.protocol.datatransfer.Receiver.opReadBlock(Receiver.java:116)
> at
> org.apache.hadoop.hdfs.protocol.datatransfer.Receiver.processOp(Receiver.java:71)
> at
> org.apache.hadoop.hdfs.server.datanode.DataXceiver.run(DataXceiver.java:249)
> at java.lang.Thread.run(Thread.java:745)
> {noformat}
> BlockSender.java:264 is shown below
> {code}
> this.volumeRef = datanode.data.getVolume(block).obtainReference();
> {code}
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