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https://issues.apache.org/jira/browse/HDFS-9149?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14941243#comment-14941243
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He Xiaoqiao commented on HDFS-9149:
-----------------------------------
hi [~He Tianyi]], thank you for your comments.
{quote}
The only thing is that, I'm not aware why did getWeight designed to be like
this in the first place, i.e. whether there is some particular concern.
{quote}
maybe there is no any particular concerns. From the original implemention of
{{pseudoSortByDistance}} to
[HDFS-6268|https://issues.apache.org/jira/browse/HDFS-6268] which is first time
to restructure by {{SortByDistance}} there is no indication to consider
multi-IDC scenario.
{quote}
One simple idea is generalizes getWeight into a function that calculates
distance between two locations (more like getDistance), regardless of the
meaning of each hierarchy.
{quote}
i think it could be simple and resonable to add if statement based on
{{getWeight}}:
{code:java}
protected int getWeight(Node reader, Node node) {
- // 0 is local, 1 is same rack, 2 is off rack
+ // 0 is local, 1 is same rack, 2 is same IDC, 3 is off IDC
// Start off by initializing to off rack
- int weight = 2;
+ int weight = 3;
if (reader != null) {
if (reader.equals(node)) {
weight = 0;
} else if (isOnSameRack(reader, node)) {
weight = 1;
+ } else {
+ rParent = reader.getParent();
+ nParent = node.getParent();
+ if (null != rParent && null != nParent && isSameParent(rParent,
nParent))
+ weight = 2;
}
}
return weight;
{code}
> Consider multi datacenter when sortByDistance
> ---------------------------------------------
>
> Key: HDFS-9149
> URL: https://issues.apache.org/jira/browse/HDFS-9149
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: namenode
> Reporter: He Xiaoqiao
> Assignee: He Tianyi
>
> {{sortByDistance}} doesn't consider multi-datacenter when read data, so there
> my be reading data via other datacenter when hadoop deployment with multi-IDC.
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