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https://issues.apache.org/jira/browse/HDFS-14372?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16796766#comment-16796766
 ] 

lujie commented on HDFS-14372:
------------------------------

ping---->

cloud anyone help me review this bug?

thansk!

> NPE while DN is shutting down
> -----------------------------
>
>                 Key: HDFS-14372
>                 URL: https://issues.apache.org/jira/browse/HDFS-14372
>             Project: Hadoop HDFS
>          Issue Type: Bug
>            Reporter: lujie
>            Assignee: lujie
>            Priority: Major
>         Attachments: HDFS-14372_0.patch
>
>
> Take the code BPServiceActor#register:
> {code:java}
> while (shouldRun()) {
> try {
>    // Use returned registration from namenode with updated fields
>     newBpRegistration = bpNamenode.registerDatanode(newBpRegistration);
>     newBpRegistration.setNamespaceInfo(nsInfo);
>     bpRegistration = newBpRegistration;
>     break;
> } catch(EOFException e) { // namenode might have just restarted
>     ....
> }
> LOG.info("Block pool " + this + " successfully registered with NN");
> bpos.registrationSucceeded(this, bpRegistration);
> {code}
> if DN is shutdown, then above code will skip the loop, and bpRegistration  == 
> null, the null value will be used  in DataNode#bpRegistrationSucceeded:
> {code:java}
> if(!storage.getDatanodeUuid().equals(bpRegistration.getDatanodeUuid()))
> {code}
> hence NPE happens
> {code:java}
> java.lang.NullPointerException
> at 
> org.apache.hadoop.hdfs.server.datanode.DataNode.bpRegistrationSucceeded(DataNode.java:1583)
> at 
> org.apache.hadoop.hdfs.server.datanode.BPOfferService.registrationSucceeded(BPOfferService.java:425)
> at 
> org.apache.hadoop.hdfs.server.datanode.BPServiceActor.register(BPServiceActor.java:807)
> at 
> org.apache.hadoop.hdfs.server.datanode.BPServiceActor.connectToNNAndHandshake(BPServiceActor.java:294)
> at 
> org.apache.hadoop.hdfs.server.datanode.BPServiceActor.run(BPServiceActor.java:840)
> at java.lang.Thread.run(Thread.java:745)
> {code}



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