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https://issues.apache.org/jira/browse/HDFS-15366?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17112409#comment-17112409
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Stephen O'Donnell commented on HDFS-15366:
------------------------------------------
Looking at the code where the NPE occurred (in the version this cluster was
running), it is:
{code}
/** @return the parent directory */
public final INodeDirectory getParent() {
return parent == null? null
: parent.isReference()? getParentReference().getParent():
parent.asDirectory(); // NPE on this line
}
/**
* @return the parent as a reference if this is a referred inode;
* otherwise, return null.
*/
public INodeReference getParentReference() {
return parent == null || !parent.isReference()? null:
(INodeReference)parent;
}
{code}
If parent is null the code handles it, which suggest getParentReference() must
be returning null. Looking at the code, I don't see how it can return null.
We suspect some sort of race condition here. This problem does not occur
frequently, but there is clearly a problem somewhere.
> Active NameNode went down with NPE
> ----------------------------------
>
> Key: HDFS-15366
> URL: https://issues.apache.org/jira/browse/HDFS-15366
> Project: Hadoop HDFS
> Issue Type: Bug
> Affects Versions: 2.7.3
> Reporter: sarun singla
> Priority: Major
>
> {code:java}
> 2020-05-12 00:31:54,565 ERROR blockmanagement.BlockManager
> (BlockManager.java:run(3816)) - ReplicationMonitor thread received Runtime
> exception.
> java.lang.NullPointerException
> at org.apache.hadoop.hdfs.server.namenode.INode.getParent(INode.java:629)
> at
> org.apache.hadoop.hdfs.server.namenode.FSDirectory.getRelativePathINodes(FSDirectory.java:1009)
> at
> org.apache.hadoop.hdfs.server.namenode.FSDirectory.getFullPathINodes(FSDirectory.java:1015)
> at
> org.apache.hadoop.hdfs.server.namenode.FSDirectory.getFullPathName(FSDirectory.java:1020)
> at
> org.apache.hadoop.hdfs.server.namenode.INode.getFullPathName(INode.java:591)
> at
> org.apache.hadoop.hdfs.server.namenode.INodeFile.getName(INodeFile.java:550)
> at
> org.apache.hadoop.hdfs.server.blockmanagement.BlockManager$ReplicationWork.chooseTargets(BlockManager.java:3912)
> at
> org.apache.hadoop.hdfs.server.blockmanagement.BlockManager$ReplicationWork.access$200(BlockManager.java:3875)
> at
> org.apache.hadoop.hdfs.server.blockmanagement.BlockManager.computeReplicationWorkForBlocks(BlockManager.java:1560)
> at
> org.apache.hadoop.hdfs.server.blockmanagement.BlockManager.computeReplicationWork(BlockManager.java:1452)
> at
> org.apache.hadoop.hdfs.server.blockmanagement.BlockManager.computeDatanodeWork(BlockManager.java:3847)
> at
> org.apache.hadoop.hdfs.server.blockmanagement.BlockManager$ReplicationMonitor.run(BlockManager.java:3799)
> at java.lang.Thread.run(Thread.java:748)
> 2020-05-12 00:31:54,567 INFO util.ExitUtil (ExitUtil.java:terminate(124)) -
> Exiting with status 1
> 2020-05-12 00:31:54,621 INFO namenode.NameNode (LogAdapter.java:info(47)) -
> SHUTDOWN_MSG:
> /************************************************************
> SHUTDOWN_MSG: Shutting down NameNode at xyz.com/xxx
> ************************************************************/{code}
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