Junping Du created HADOOP-8469:
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Summary: Make NetworkTopology class pluggable and support user
specified topology class
Key: HADOOP-8469
URL: https://issues.apache.org/jira/browse/HADOOP-8469
Project: Hadoop Common
Issue Type: Sub-task
Affects Versions: 2.0.0-alpha, 1.0.0
Reporter: Junping Du
Assignee: Junping Du
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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