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https://issues.apache.org/jira/browse/HDFS-13811?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16985378#comment-16985378
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Yiqun Lin commented on HDFS-13811:
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{quote}
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) ?
{quote}
Yes, the usage in web UI fetched from mount table entry stored in state store?
The update service update the quota usage value periodically, so we can see
near real-time usage value. The [~dibyendu_hadoop]'s way is that get usage
value from RouterQuotaManager when querying mount table entries from state
store.
> 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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