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https://issues.apache.org/jira/browse/HDFS-8688?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14629702#comment-14629702
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Walter Su commented on HDFS-8688:
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Thanks [~mingma] for review!
I checked 《Hadoop: The Definitive Guide》 about
rackawareness/DNSToSwitchMapping. "switch" and "rack" are a little different.
(I didn't fully read the book, what I said may have some error. Following are
my understanding, not from the book)
Suppose our configuration is "typical two-level netowrk architecture", I'll
assume "switch" and "rack" are the same.
"the script name == null implies single rack" ,,,, That's true.
However if scriptName !=null, we can't tell if it's a single switch/rack. So
{{ScriptBasedMapping#isSingleSwitch()}} is flawed. It need a fix.
As I said before, "switch" and "rack" are a little different.
"switch" is a logic in DNSToSwitchMapping
"rack" is a logic in NetworkTopology
We can't assume every user uses "typical two-level netowrk architecture".
That's first reason we had better keep isSingleSwitch() API.
The API is provided by hadoop-common, that's the second reason.
> replace shouldCheckForEnoughRacks with hasClusterEverBeenMultiRack
> ------------------------------------------------------------------
>
> Key: HDFS-8688
> URL: https://issues.apache.org/jira/browse/HDFS-8688
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Reporter: Walter Su
> Assignee: Walter Su
> Attachments: HDFS-8688.01.patch, HDFS-8688.02.patch
>
>
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