Improve the rack-aware replica placement performance
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Key: HADOOP-972
URL: https://issues.apache.org/jira/browse/HADOOP-972
Project: Hadoop
Issue Type: Improvement
Components: dfs
Affects Versions: 0.11.0
Reporter: Hairong Kuang
Assigned To: Hairong Kuang
Fix For: 0.12.0
This issue aims to improve the rack-aware replica placement performance. A
major idea is to avoid constructing lists of possible targets for random
selection in chooseTarget, which currently needs interating all
DatanodeDescriptors. I plan to change the NetworkTopology data structure as
follow:
1. each InnerNode stores its childrens as a list;
2. each InnerNode adds a new field numberOfLeaves the total number of leaves
(i.e. data nodes) in its subtree.
NetworkTopology will support two new methods:
1. DatanodeDescriptor chooseRandom( String scope): it randomly choose one leave
from scope.
2. DatanodeDescriptor chooseRandomExclude(String excludedScope): it randomly
choose one leave from ~scope
In addition, Issue 971 will also help improve the performance of the rack-aware
DFS patch.
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