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https://issues.apache.org/jira/browse/HDFS-8647?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14962697#comment-14962697
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Ming Ma commented on HDFS-8647:
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Most of the test failures are due to mismatch between BlockManager and function
definition of {{chooseReplicasToDelete}}; BlockManager should swap
{{addedNode}} and {{delNodeHint}}.
After the fix, the only failed unit test left is
{{TestBalancer#testBalancerWithPinnedBlocks}}. Can you please investigate if it
is related to the patch?
Nits:
* {{public}} can be removed from {{public DatanodeStorageInfo
chooseReplicaToDelete}}.
* {{final List<DatanodeStorageInfo> moreThanOne = new
ArrayList<DatanodeStorageInfo>();}} Given hadoop uses JDK7, you can simplify
this with type inference {{final List<DatanodeStorageInfo> moreThanOne = new
ArrayList<>();}} Same for other places in the patch.
* {{chooseReplicaToDelete}}’s parameter {{Collection<DatanodeStorageInfo>
first}}. How about name it {{moreThanOne}} instead? Similarly for {{second}}.
> Abstract BlockManager's rack policy into BlockPlacementPolicy
> -------------------------------------------------------------
>
> Key: HDFS-8647
> URL: https://issues.apache.org/jira/browse/HDFS-8647
> Project: Hadoop HDFS
> Issue Type: Improvement
> Reporter: Ming Ma
> Assignee: Brahma Reddy Battula
> Attachments: HDFS-8647-001.patch, HDFS-8647-002.patch,
> HDFS-8647-003.patch, HDFS-8647-004.patch, HDFS-8647-004.patch,
> HDFS-8647-005.patch, HDFS-8647-006.patch
>
>
> Sometimes we want to have namenode use alternative block placement policy
> such as upgrade domains in HDFS-7541.
> BlockManager has built-in assumption about rack policy in functions such as
> useDelHint, blockHasEnoughRacks. That means when we have new block placement
> policy, we need to modify BlockManager to account for the new policy. Ideally
> BlockManager should ask BlockPlacementPolicy object instead. That will allow
> us to provide new BlockPlacementPolicy without changing BlockManager.
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