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https://issues.apache.org/jira/browse/HDFS-5782?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Joe Pallas reassigned HDFS-5782:
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Assignee: Joe Pallas (was: David Powell)
> BlockListAsLongs should take lists of Replicas rather than concrete classes
> ---------------------------------------------------------------------------
>
> Key: HDFS-5782
> URL: https://issues.apache.org/jira/browse/HDFS-5782
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: datanode
> Affects Versions: 3.0.0
> Reporter: David Powell
> Assignee: Joe Pallas
> Priority: Minor
> Attachments: HDFS-5782.patch, HDFS-5782.patch
>
>
> From HDFS-5194:
> {quote}
> BlockListAsLongs's constructor takes a list of Blocks and a list of
> ReplicaInfos. On the surface, the former is mildly irritating because it is
> a concrete class, while the latter is a greater concern due to being a
> File-based implementation of Replica.
> On deeper inspection, BlockListAsLongs passes members of both to an internal
> method that accepts just Blocks, which conditionally casts them *back* to
> ReplicaInfos (this cast only happens to the latter, though this isn't
> immediately obvious to the reader).
> Conveniently, all methods called on these objects are found in the Replica
> interface, and all functional (i.e. non-test) consumers of this interface
> pass in Replica subclasses. If this constructor took Lists of Replicas
> instead, it would be more generally useful and its implementation would be
> cleaner as well.
> {quote}
> Fixing this indeed makes the business end of BlockListAsLongs cleaner while
> requiring no changes to FsDatasetImpl. As suggested by the above
> description, though, the HDFS tests use BlockListAsLongs differently from the
> production code -- they pretty much universally provide a list of actual
> Blocks. To handle this:
> - In the case of SimulatedFSDataset, providing a list of Replicas is actually
> less work.
> - In the case of NNThroughputBenchmark, rewriting to use Replicas is fairly
> invasive. Instead, the patch creates a second constructor in
> BlockListOfLongs specifically for the use of NNThrougputBenchmark. It turns
> the stomach a little, but is clearer and requires less code than the
> alternatives (and isn't without precedent).
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