Yongjun Zhang created HDFS-7497:
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Summary: Inconsistent report of decommissioning DataNodes between
dfsadmin and NameNode webui
Key: HDFS-7497
URL: https://issues.apache.org/jira/browse/HDFS-7497
Project: Hadoop HDFS
Issue Type: Bug
Components: datanode, namenode
Reporter: Yongjun Zhang
Assignee: Yongjun Zhang
It's observed that dfsadmin report list DNs in the decomm state while NN UI
list DNs in dead state.
I found what happens is:
NN webui uses two steps to get the result:
* first collect a list of all alive DNs,
* traverse through all live DNs to find decommissioning DNs.
It calls the following method to decide whether a DN is dead or alive:
{code}
/** Is the datanode dead? */
boolean isDatanodeDead(DatanodeDescriptor node) {
return (node.getLastUpdate() <
(Time.now() - heartbeatExpireInterval));
}
{code}
On the other hand, dfsadmin traverse all DNs to find to all decommissioning DNs
(check whether a DN is in {{AdminStates.DECOMMISSION_INPROGRESS}} state),
without checking whether a DN is dead or alive like above.
The problem is, when a DN is determined to be dead, its state may still be
{{AdminStates.DECOMMISSION_INPROGRESS}} .
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