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https://issues.apache.org/jira/browse/HDFS-11530?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15971764#comment-15971764
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Arpit Agarwal commented on HDFS-11530:
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Thanks for updating the patch [~linyiqun]. A few more comments:
# BlockPlacementPolicyDefault#chooseRandom, the continuation in the {{for}}
loop at line 719 looks unnecessary. If we fail to place a block for the first
storage type then the function is guaranteed to fail later, correct?
# DatanodeManager.java: DFSNetworkTopology.getInstance - can this method be
simplified? We shouldn't use different initialization paths with reflection.
Why not just define a method that returns the node factory for NetworkTopology
and override it in DfsNetworkTopology? Then you can just call
{{nt.init(nt.getNodeFactory())}} or something similar. Also the getInstance
method should not reside in DFSNetworkTopology. We should avoid
reflection/class hierarchy knowledge whenever possible.
# DatanodeDescriptor.java: The reflection checks at lines 503 and 901 also make
me sad. However, I can't think of a better solution that works for branch-2 as
Java 7 interfaces lack default methods...
> Use HDFS specific network topology to choose datanode in
> BlockPlacementPolicyDefault
> ------------------------------------------------------------------------------------
>
> Key: HDFS-11530
> URL: https://issues.apache.org/jira/browse/HDFS-11530
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: namenode
> Affects Versions: 3.0.0-alpha2
> Reporter: Yiqun Lin
> Assignee: Yiqun Lin
> Attachments: HDFS-11530.001.patch, HDFS-11530.002.patch,
> HDFS-11530.003.patch, HDFS-11530.004.patch, HDFS-11530.005.patch,
> HDFS-11530.006.patch, HDFS-11530.007.patch, HDFS-11530.008.patch,
> HDFS-11530.009.patch, HDFS-11530.010.patch, HDFS-11530.011.patch
>
>
> The work for {{chooseRandomWithStorageType}} has been merged in HDFS-11482.
> But this method is contained in new topology {{DFSNetworkTopology}} which is
> specified for HDFS. We should update this and let
> {{BlockPlacementPolicyDefault}} use the new way since the original way is
> inefficient.
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