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https://issues.apache.org/jira/browse/HADOOP-16161?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16840523#comment-16840523
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He Xiaoqiao commented on HADOOP-16161:
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Thanks [~elgoiri] for the review and commit.
> NetworkTopology#getWeightUsingNetworkLocation return unexpected result
> ----------------------------------------------------------------------
>
> Key: HADOOP-16161
> URL: https://issues.apache.org/jira/browse/HADOOP-16161
> Project: Hadoop Common
> Issue Type: Bug
> Components: net
> Reporter: He Xiaoqiao
> Assignee: He Xiaoqiao
> Priority: Major
> Fix For: 3.3.0
>
> Attachments: HADOOP-16161.001.patch, HADOOP-16161.002.patch,
> HADOOP-16161.003.patch, HADOOP-16161.004.patch, HADOOP-16161.005.patch,
> HADOOP-16161.006.patch, HADOOP-16161.007.patch, HADOOP-16161.008.patch,
> HADOOP-16161.009.patch
>
>
> Consider the following scenario:
> 1. there are 4 slaves and topology like:
> Rack: /IDC/RACK1
> hostname1
> hostname2
> Rack: /IDC/RACK2
> hostname3
> hostname4
> 2. Reader from hostname1, and calculate weight between reader and [hostname1,
> hostname3, hostname4] by #getWeight, and their corresponding values are
> [0,4,4]
> 3. Reader from client which is not in the topology, and in the same IDC but
> in none rack of the topology, and calculate weight between reader and
> [hostname1, hostname3, hostname4] by #getWeightUsingNetworkLocation, and
> their corresponding values are [2,2,2]
> 4. Other different Reader can get the similar results.
> The weight result for case #3 is obviously not the expected value, the truth
> is [4,4,4]. this issue may cause reader not really following arrange: local
> -> local rack -> remote rack.
> After dig the detailed implement, the root cause is
> #getWeightUsingNetworkLocation only calculate distance between Racks rather
> than hosts.
> I think we should add constant 2 to correct the weight of
> #getWeightUsingNetworkLocation.
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