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https://issues.apache.org/jira/browse/HDFS-13811?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16694887#comment-16694887
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Yiqun Lin edited comment on HDFS-13811 at 11/21/18 4:08 PM:
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Take a quick look for the patch, looks like we change a lot. Thinking again for
the corner case mentioned, can we use a more easier way:
1) When prepare to update mount tables in
RouterQuotaUpdateService#updateMountTableEntries, get the latest mount table
entries in quota update service.
2) When latest quota value is not matched with fetched before, then generate a
new quota value(use latest quota and latest quota usage).
I mean we can just take an additional check when updating the quota usage in
update service. At least one thing we should promise: admin cmd be respected
and making sense..
If this way is okay, I'm not sure other change is really needed.
Please let me know your thought, [~dibyendu_hadoop]. I think this way can
address your case.
was (Author: linyiqun):
Take a quick look for the patch, looks like we change a lot. Thinking again for
the corner case mentioned, can we use a more easier way:
1) When prepare to update mount tables in
RouterQuotaUpdateService#updateMountTableEntries, get the latest mount table
entries in quota update service.
2) When latest quota value is not matched with fetched before, then generate a
new quota value.
I mean we can just take an additional check when updating the quota usage in
update service. At least one thing we should promise: admin cmd be respected
and making sense..
If this way is okay, I'm not sure other change is really needed.
Please let me know your thought, [~dibyendu_hadoop]. I think this way can
address your case.
> 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: Dibyendu Karmakar
> Priority: Major
> Attachments: HDFS-13811-000.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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