[HDFS-14372] NPE while DN is shutting down

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 3.3.0
• Assignee: lujie
• Reporter: lujie
• Created: 14/Mar/19 12:09
• Updated: 05/May/19 11:24
• Resolved: 05/May/19 11:11

Description

Take the code BPServiceActor#register:

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);

if DN is shutdown, then above code will skip the loop, and bpRegistration  == null, the null value will be used  in DataNode#bpRegistrationSucceeded:

if(!storage.getDatanodeUuid().equals(bpRegistration.getDatanodeUuid()))

hence NPE happens

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)