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