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https://issues.apache.org/jira/browse/HDFS-9807?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15992494#comment-15992494
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Ewan Higgs commented on HDFS-9807:
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Thanks [~virajith]! This is good stuff.
In your solution using {{BlockPlacementPolicy}} and a static variable to record
the block, I had considered such a solution but was concerned that this will
break when running tests in parallel if we have multiple test cases. As it
stands, we only have the one test so it should be fine; but if someone adds
another test using the same {{BlockPlacementPolicy}} there is a risk that we
introduce some flakiness into the testing infrastructure.
As per your previous question about why I had removed {{final}} from arguments
in a function. This is because checkstyle complained that I had added redundant
{{final}} decls to a function argument, and I figured that if someone deigned
to turn that warning on in checkstyle then I should fix it where I'm touching
the code.
For other people watching along: findbugs is bugged; the issues reported are
not touched/introduced by this patch afaict. Same with the unit tests.
> Add an optional StorageID to writes
> -----------------------------------
>
> Key: HDFS-9807
> URL: https://issues.apache.org/jira/browse/HDFS-9807
> Project: Hadoop HDFS
> Issue Type: Improvement
> Affects Versions: 3.0.0-alpha2
> Reporter: Chris Douglas
> Assignee: Ewan Higgs
> Attachments: HDFS-9807.001.patch, HDFS-9807.002.patch,
> HDFS-9807.003.patch, HDFS-9807.004.patch, HDFS-9807.005.patch,
> HDFS-9807.006.patch, HDFS-9807.007.patch, HDFS-9807.008.patch,
> HDFS-9807.009.patch
>
>
> The {{BlockPlacementPolicy}} considers specific storages, but when the
> replica is written the DN {{VolumeChoosingPolicy}} is unaware of any
> preference or constraints from other policies affecting placement. This
> limits heterogeneity to the declared storage types, which are treated as
> fungible within the target DN. It should be possible to influence or
> constrain the DN policy to select a particular storage.
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