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https://issues.apache.org/jira/browse/HADOOP-8469?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13289713#comment-13289713
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Tsz Wo (Nicholas), SZE commented on HADOOP-8469:
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Hi Junping, thanks a lot for the update. It is much easier to see what have
been changed in InnerNode. Some comments:
- Let's rename net.topology.class.name to net.topology.impl (which is
consistent to other keys like fs.file.impl.)
- NET_TOPOLOGY_WITH_NODEGROUP is not used. What is it for?
- Could you change InnerNode.children to List<Node>? This is a problem on the
existing code.
- Why doGetRack(loc) is needed instead of letting subclasses overriding
getRack(loc) directly?
- Let's rename compareParents(..) to isSameParent(..). You may want to change
the javadoc to "@return true if their parents are equal, ..."
- Please move isOnSameNodeGroup(..) to right after isNodeGroupAware(..) and
change the comment above isOnSameNodeGroup(..) to javadoc.
> Make NetworkTopology class pluggable
> ------------------------------------
>
> Key: HADOOP-8469
> URL: https://issues.apache.org/jira/browse/HADOOP-8469
> Project: Hadoop Common
> Issue Type: Sub-task
> Affects Versions: 1.0.0, 2.0.0-alpha
> Reporter: Junping Du
> Assignee: Junping Du
> Attachments: HADOOP-8469-NetworkTopology-pluggable-v2.patch,
> HADOOP-8469-NetworkTopology-pluggable-v3.patch,
> HADOOP-8469-NetworkTopology-pluggable.patch
>
>
> The class NetworkTopology is where the three-layer hierarchical topology is
> modeled in the current code base and is instantiated directly by the
> DatanodeManager and Balancer.
> To support alternative topologies, changes were make the topology class
> pluggable, that is to support using a user specified topology class specified
> in the Hadoop configuration file core-defaul.xml. The user specified topology
> class is instantiated using reflection in the same manner as other
> customizable classes in Hadoop. If no use specified topology class is found,
> the fallback is to use the NetworkTopology to preserve current behavior. To
> make it possible to reuse code in NetworkTopology several minor changes were
> made to make the class more extensible. The NetworkTopology class is
> currently annotated with @InterfaceAudience.LimitedPrivate({"HDFS",
> "MapReduce"}) and @InterfaceStability.Unstable.
> The proposed changes in NetworkTopology listed below
> 1. Some fields were changes from private to protected
> 2. Added some protected methods so that sub classes could override behavior
> 3. Added a new method,isNodeGroupAware,to NetworkTopology
> 4. The inner class InnerNode was made a package protected class to it would
> be easier to subclass
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