Jinglun created HDFS-15809:
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             Summary: DeadNodeDetector doesn't remove live nodes from dead node 
set.
                 Key: HDFS-15809
                 URL: https://issues.apache.org/jira/browse/HDFS-15809
             Project: Hadoop HDFS
          Issue Type: Bug
            Reporter: Jinglun


We found the dead node detector might never remove the alive nodes from the 
dead node set in a big cluster. For example:
 # 200 nodes are added to the dead node set by DeadNodeDetector.
 # DeadNodeDetector#checkDeadNodes() adds 100 nodes to the deadNodesProbeQueue 
because the queue limited length is 100.
 # The probe threads start working and probe 30 nodes.
 # DeadNodeDetector#checkDeadNodes() is scheduled again. It iterates the dead 
node set  and adds 30 nodes to the deadNodesProbeQueue. But the order is the 
same as the last time. So the 30 nodes that has already been probed are added 
to the queue again.
 # Repeat 3 and 4. But we always add the first 30 nodes from the dead set. If 
they are all dead then the live nodes behind them could never be recovered.



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