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https://issues.apache.org/jira/browse/HDFS-15196?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17050523#comment-17050523
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Fengnan Li commented on HDFS-15196:
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Agree the order should be preserved. Just to be clear, I list out cases below.
*Expected*: the order was lexicographical order of children names, including
all namenode listing and mount points, even with batch listings.
*Before this patch*: the order was lexicographical of children names plus mount
points, with some namenode listings skipped or infinite loop.
*After this patch*: before the last batch, the order is lexicographical. For
the last batch, mount points is added into the structure which is a TreeMap
indexed by the children names, thus the order is kept in this batch but not
across batches. I think there are two ways this can be solved.
# Clients call router once and all of the batch listing is controlled between
router and namenode, thus with a global TreeMap the order is kept before
sending back to clients.
# Client side needs a change, ex. DistributedFileSystem.java to use a treemap
instead of list to maintain the order.
I think 1 is the way since we don't want to change the client logic
What are your thoughts? [~elgoiri] [~ayushtkn]
{quote}We may want to also test the limit in the Router side.
{quote}
What is the limit to test?
> 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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