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https://issues.apache.org/jira/browse/HADOOP-985?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12473574
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Hairong Kuang commented on HADOOP-985:
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The patch looks good. I have two comments:
1. ClientProtocolVersionNumber should be bumped since the syntax of the open &
create requests is changed.
2. DatanodeID contains the fields that need to be saved to the disk. Since the
new field hostName does not need to serialized, it might better be put in
DatanodeDescriptor.
> Namenode should identify DataNodes as ip:port instead of hostname:port
> ----------------------------------------------------------------------
>
> Key: HADOOP-985
> URL: https://issues.apache.org/jira/browse/HADOOP-985
> Project: Hadoop
> Issue Type: Improvement
> Components: dfs
> Affects Versions: 0.11.0
> Reporter: Raghu Angadi
> Assigned To: Raghu Angadi
> Fix For: 0.12.0
>
> Attachments: dfshealth.html, HADOOP-985-1.patch, HADOOP-985-2.patch,
> HADOOP-985-3.patch, HADOOP-985-4.patch
>
>
> Right now NameNode keeps track of DataNodes with "hostname:port". One
> proposal is to keep track of datanodes with "ip:port". There are various
> concerns expressed regd hostnames and ip. Please add your experiences here so
> that we have better idea on what we should fix etc.
> How should be calculate datanode ip:
> 1) Just like how we calculate hostname currently with
> "dfs.datanode.dns.interface" and "dfs.datanode.dns.nameserver". So if
> interface specified wrong, it could report ip like 127.0.0.1 which might or
> might not be intended.
> 2) Namenode can use the remove socket address when the datanode
> registers. Not sure how easy it to get this address in RPC or if this is
> desirable.
> 3) Namenode could just resolve the hostname when a datanode
> registers. It could print of a warning if the resolved ip and reported ip
> don't match.
> One advantage of using IPs is that DFSClient does not need to resolve them
> when it connects to datanode. This could save few milliseconds for each
> block. Also, DFSClient should check all its ips to see if a given ip is local
> or not.
> As far I see namenode does not resolve any DNS in normal operations since it
> does not actively contact datanodes. In that sense not sure if this have any
> change in Namenode performance.
> Thoughts?
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