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https://issues.apache.org/jira/browse/HDFS-13811?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16984780#comment-16984780
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Jinglun commented on HDFS-13811:
--------------------------------

Hi [~linyiqun], thanks your comments ! I didn't think about the web UI before, 
thanks your reminding !

I haven't looked into the code, just a guess: is the web UI usage fetched from 
the state store now ? Might be we can display the usage from the local 
cache(RouterQuotaManager) ? 

I had a look of [~dibyendu_hadoop]'s way but not in detail. I'll try to figure 
out how it works and how to fix the web UI this weekend.

> RBF: Race condition between router admin quota update and periodic quota 
> update service
> ---------------------------------------------------------------------------------------
>
>                 Key: HDFS-13811
>                 URL: https://issues.apache.org/jira/browse/HDFS-13811
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>            Reporter: Dibyendu Karmakar
>            Assignee: Jinglun
>            Priority: Major
>         Attachments: HDFS-13811-000.patch, HDFS-13811-HDFS-13891-000.patch, 
> HDFS-13811.001.patch, HDFS-13811.002.patch, HDFS-13811.003.patch
>
>
> If we try to update quota of an existing mount entry and at the same time 
> periodic quota update service is running on the same mount entry, it is 
> leading the mount table to _inconsistent state._
> Here transactions are:
> A - Quota update service is fetching mount table entries.
> B - Quota update service is updating the mount table with current usage.
> A' - User is trying to update quota using admin cmd.
> and the transaction sequence is [ A A' B ]
> quota update service is updating the mount table with old quota value.



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