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From "Yiqun Lin (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-11482) Add storage type demand to into DFSNetworkTopology#chooseRandom
Date Thu, 09 Mar 2017 10:59:37 GMT

    [ https://issues.apache.org/jira/browse/HDFS-11482?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15902875#comment-15902875
] 

Yiqun Lin commented on HDFS-11482:
----------------------------------

Thanks [~vagarychen] for the explanation and thanks for updating the patch. The latest patch
looks almost good now.
Only three minor comments from me:

* Would you use {{RANDOM}} to replace {{r}}?
{code}
 public class DFSNetworkTopology extends NetworkTopology {
+
+  private static final Random r = new Random();
{code}
* This position of the following comment seems not correct in the latest patch, it should
be updated like following:
{code}
+    } else {
        // the children are inner nodes 
+      ArrayList<DFSTopologyNodeImpl> candidates =
+          getEligibleChildren(root, excludeRoot, type);   
+      if (candidates.size() == 0) {
+        return null;
+      }
{code}
* Can you please add one more test case with the scope that start with {{"~"}}? This new test
is used to test the method {{public Node chooseRandomWithStorageType(final String scope, final
Collection<Node> excludedNodes, StorageType type)}}. Now I see this test is missing.

{quote}
I think we can reduce iteration e.g in getSubtreeStorageCount by maintaining more aggregate
state at...
{quote}
BTW, also +1 for this idea.

> Add storage type demand to into DFSNetworkTopology#chooseRandom
> ---------------------------------------------------------------
>
>                 Key: HDFS-11482
>                 URL: https://issues.apache.org/jira/browse/HDFS-11482
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: namenode
>            Reporter: Chen Liang
>            Assignee: Chen Liang
>         Attachments: HDFS-11482.001.patch, HDFS-11482.002.patch, HDFS-11482.003.patch,
HDFS-11482.004.patch, HDFS-11482.005.patch, HDFS-11482.006.patch
>
>
> HDFS-11450 adds storage type info into network topology, with on this info we may change
chooseRandom to take storage type requirement as parameter, only checking subtrees required
storage type available. This way we avoid blindly picking up nodes that are not applicable.



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