[
https://issues.apache.org/jira/browse/HDFS-6268?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13985090#comment-13985090
]
Aaron T. Myers commented on HDFS-6268:
--------------------------------------
The latest patch looks good to me. +1 pending answers to Yongjun's questions.
I do have one high-level comment, though feel free to ignore it: I do wonder if
all of {{pseudoSortByDistance}} couldn't be fairly substantially simplified by
first separating the input nodes into separate lists of
local/rack-local/non-rack-local nodes, and then once that's done constructing a
new list by pulling from these separate lists in the appropriate order, and
potentially shuffling the latter two lists as is the goal of this JIRA. I
suspect the code could be made much more readable if we were to do it that way,
and now might be a decent time to do it since this is a fairly substantial
rewrite of this method.
> Better sorting in NetworkTopology#pseudoSortByDistance when no local node is
> found
> ----------------------------------------------------------------------------------
>
> Key: HDFS-6268
> URL: https://issues.apache.org/jira/browse/HDFS-6268
> Project: Hadoop HDFS
> Issue Type: Improvement
> Affects Versions: 2.4.0
> Reporter: Andrew Wang
> Assignee: Andrew Wang
> Priority: Minor
> Attachments: hdfs-6268-1.patch, hdfs-6268-2.patch
>
>
> In NetworkTopology#pseudoSortByDistance, if no local node is found, it will
> always place the first rack local node in the list in front.
> This became an issue when a dataset was loaded from a single datanode. This
> datanode ended up being the first replica for all the blocks in the dataset.
> When running an Impala query, the non-local reads when reading past a block
> boundary were all hitting this node, meaning massive load skew.
--
This message was sent by Atlassian JIRA
(v6.2#6252)
