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https://issues.apache.org/jira/browse/HDFS-1905?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13032760#comment-13032760
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Sanjay Radia commented on HDFS-1905:
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I think we are mixing the nice name with the original motivation of clusterid:
clusterId ensures that the system automatically
detects misconfigured DNs and NN by the clusterid (as the namespaceid used to
do).
We recently had an operator who did that; the system detected this and told
him that the namespace ids do not match. The operator then did a sshall to all
datanodes to change the namespace id; of course the NN accepted the "wrong
DNs" and promptly started to delete the blocks.
A more descriptive name would have helped. But lets not mix the two.
With Todd's q on rennaming the nice name I realize that a smart operator may
decided that he wants to switch the names of 2 clusters and therefore does a
quick rename on both NNs. If he makes a mistake about which DNs are connected
to which cluster a disaster could occur. A clusterId is a birthmark -- keep it
fixed forever unless you want to merge two clusters. Keep the nice name
separate from the clusterid.
> Improve the usability of namenode -format
> ------------------------------------------
>
> Key: HDFS-1905
> URL: https://issues.apache.org/jira/browse/HDFS-1905
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: name-node
> Affects Versions: 0.23.0
> Reporter: Bharath Mundlapudi
> Assignee: Bharath Mundlapudi
> Priority: Minor
> Fix For: 0.23.0
>
>
> While setting up 0.23 version based cluster, i ran into this issue. When i
> issue a format namenode command, which got changed in 23, it should let the
> user know to how to use this command in case where complete options were not
> specified.
> ./hdfs namenode -format
> I get the following error msg, still its not clear what and how user should
> use this command.
> 11/05/09 15:36:25 ERROR namenode.NameNode:
> java.lang.IllegalArgumentException: Format must be provided with clusterid
> at
> org.apache.hadoop.hdfs.server.namenode.NameNode.format(NameNode.java:1483)
> at
> org.apache.hadoop.hdfs.server.namenode.NameNode.createNameNode(NameNode.java:1623)
> at
> org.apache.hadoop.hdfs.server.namenode.NameNode.main(NameNode.java:1689)
>
> The usability of this command can be improved.
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