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https://issues.apache.org/jira/browse/HDFS-15196?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17049928#comment-17049928
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Fengnan Li commented on HDFS-15196:
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[~elgoiri] Without the fix the test will fail. Actually,
https://issues.apache.org/jira/browse/HDFS-14739 introduced a bug that makes ls
goes into an possible infinite loop since Mount table point was added as a
qualified path with parent, making the startAfter always smallest string from
across all children listings.
For example, in my test, with the ls limit as 5 from namenode. it will first
return file-0, file-1, file-2, file-3 and file-4. Without the fix,
/parent/file-7 would be added to the listing, making the next batch listing
with startAfter as `/parent/file-7` which is even smaller than file-0, thus the
query sent to downstream namenode will return file-[0-4] again. With this fix
there won't be such an issue.
I guess there is a reason that the mount point is appended as a dir, but I
haven't dug too much. After this one I will go there.
[~ayushtkn] The result was put into a TreeMap before returning so the order is
preserved.
> RBF: RouterRpcServer getListing cannot list large dirs correctly
> ----------------------------------------------------------------
>
> Key: HDFS-15196
> URL: https://issues.apache.org/jira/browse/HDFS-15196
> Project: Hadoop HDFS
> Issue Type: Bug
> Reporter: Fengnan Li
> Assignee: Fengnan Li
> Priority: Critical
> Attachments: HDFS-15196.001.patch, HDFS-15196.002.patch,
> HDFS-15196.003.patch, HDFS-15196.003.patch, HDFS-15196.004.patch,
> HDFS-15196.005.patch
>
>
> In RouterRpcServer, getListing function is handled as two parts:
> # Union all partial listings from destination ns + paths
> # Append mount points for the dir to be listed
> In the case of large dir which is bigger than DFSConfigKeys.DFS_LIST_LIMIT
> (with default value 1k), the batch listing will be used and the startAfter
> will be used to define the boundary of each batch listing. However, step 2
> here will add existing mount points, which will mess up with the boundary of
> the batch, thus making the next batch startAfter wrong.
> The fix is just to append the mount points when there is no more batch query
> necessary.
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