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https://issues.apache.org/jira/browse/HDFS-3224?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13472817#comment-13472817
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Suresh Srinivas commented on HDFS-3224:
---------------------------------------
There are three elements in DN identity - Storage ID, host address and transfer
port. When storage ID does not change and other two elements change, it is
correctly handled by the namenode.
When storage ID changes:
# Old behavior: remove any DN with matching host address (no transfer address)
## In case of single DN on the same host, correct DN is removed
## In case of multiple DNs on the same host, {color:red}a random DN is
removed{color}
# Current behavior: remove any DN with matching host address + transfer address
## In case of single DN on the same host, {color:red} no DN is removed{color}
## In case of multiple DNs on the same host, {color:red}no DN is removed{color}
# Behavior with this patch: remove any DN with matching host address + transfer
address
## In case of single DN on the same host, correct DN is removed
## In case of multiple DNs on the same host, correct DN is removed
When Storage ID changes with IP address and/or transfer address, we will end up
having two entries. I do not think this can be avoided.
I have seen cases in many setups where multiple DNs are being run on the same
machine. Given this, I prefer the new behavior with this patch.
> Bug in check for DN re-registration with different storage ID
> -------------------------------------------------------------
>
> Key: HDFS-3224
> URL: https://issues.apache.org/jira/browse/HDFS-3224
> Project: Hadoop HDFS
> Issue Type: Bug
> Reporter: Eli Collins
> Assignee: Jason Lowe
> Priority: Minor
> Attachments: HDFS-3224.patch, HDFS-3224.patch, HDFS-3224.patch
>
>
> DatanodeManager#registerDatanode checks the host to node map using an IP:port
> key, however the map is keyed on IP, so this check will always fail. It's
> performing the check to determine if a DN with the same IP and storage ID has
> already registered, and if so to remove this DN from the map and indicate
> that eg it's no longer hosting these blocks. This bug has been here forever.
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