He Xiaoqiao created HDFS-8992:
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Summary: Balancer throws NPE
Key: HDFS-8992
URL: https://issues.apache.org/jira/browse/HDFS-8992
Project: Hadoop HDFS
Issue Type: Bug
Components: balancer & mover
Affects Versions: 2.4.1
Reporter: He Xiaoqiao
Balancer may throw NPE because the following {{if Statements}}
{code:java|firstline=705}
synchronized (block) {
// update locations
for (String datanodeUuid : blk.getDatanodeUuids()) {
final BalancerDatanode d = datanodeMap.get(datanodeUuid);
if (datanode != null) { // not an unknown datanode
block.addLocation(d);
}
}
}
{code}
Before moving block, Balancer divides into two step to get all DNs info & some
blocks of DN from NN. Regarding one DN commission after {{getDatanodeReport}}
then {{getBlockList}} and one block's target is above DN just right, It will
throw NPE when dispatcher.
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