[
https://issues.apache.org/jira/browse/HADOOP-11676?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14359874#comment-14359874
]
Walter Su commented on HADOOP-11676:
------------------------------------
Thanks [~zhz] for thorough review. Good point using ArrayList instead of a
HashSet. Also because racks.add is more often, and racks.remove is less often,
there is no performance issue using ArrayList. And sorry for lack of code
comments.
Thanks [~aw], we should deal with HDFS expansion very carefully. Thanks [~zhz]
again for answering the question.
> Add API to NetworkTopology for getting all racks
> ------------------------------------------------
>
> Key: HADOOP-11676
> URL: https://issues.apache.org/jira/browse/HADOOP-11676
> Project: Hadoop Common
> Issue Type: Sub-task
> Reporter: Walter Su
> Assignee: Walter Su
> Attachments: HADOOP-11676.patch
>
>
> The existing two NetworkTopology.chooseRandom(..) API support choosing node
> from scope and choosing outside scope. BlockPlacementPolicyDefault class use
> these two API to choose node from one rack or choose outside one rack.
> We want to implement a new placement policy called
> BlockPlacementPolicyFaultTolerant which tries its best to place replicas to
> most racks. To achieve this, We need to know how many replicas each rack has.
> And first, we need to get all racks.
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
