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https://issues.apache.org/jira/browse/HDFS-8647?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14803246#comment-14803246
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Brahma Reddy Battula commented on HDFS-8647:
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{{TestBlocksWithNotEnoughRacks}} are failing due to following cases.
*Before change*
if cluster was multi rack first and then later became single rack, then those
blocks were getting added in {{NeededReplications}}, and the same value was
expected in tests.
a. But this was only till the namenode was alive. If NN was restarted after
making into single rack, this {{NeededReplications}} will not have the block.
b. And before NN restart, another rack was added, then auto replication
happens to new rack. But Once NN restarted, and new rack added, then auto
replication to new rack (if single rack have already enough replicas == RF) to
new rack happens only if RF changes on those blocks.
*After change*
it will not add to {{NeededReplications}} immediately cluster became the single
rack.
a. After change, auto replication (if single rack have already enough
replicas == RF) will not happen when the cluster is added with one more rack.
Only this will be triggered only if RF changes on those blocks.
If new change is Okay, then test case can be updated, else patch can be updated.
> 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
>
>
> 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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