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https://issues.apache.org/jira/browse/HDFS-14372?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16806085#comment-16806085
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Ayush Saxena commented on HDFS-14372:
-------------------------------------
Thanx [~xiaoheipangzi] for the patch.
I guess in the UT there is no need to catch the NPE and for the IOE you may
assert the expected Exception message, rather than just logging it.
> 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, HDFS-14372_1.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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