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From "Hudson (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-5782) BlockListAsLongs should take lists of Replicas rather than concrete classes
Date Thu, 15 Jan 2015 15:10:41 GMT

    [ https://issues.apache.org/jira/browse/HDFS-5782?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14278769#comment-14278769

Hudson commented on HDFS-5782:

FAILURE: Integrated in Hadoop-Mapreduce-trunk-Java8 #75 (See [https://builds.apache.org/job/Hadoop-Mapreduce-trunk-Java8/75/])
HDFS-5782. Change BlockListAsLongs constructor to take Replica as parameter type instead of
concrete classes Block and ReplicaInfo.  Contributed by David Powell and Joe Pallas (szetszwo:
rev 6464a8929a3623e49155febf2f9817253f9a1de3)
* hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
* hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/NNThroughputBenchmark.java
* hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestBlockHasMultipleReplicasOnSameDN.java
* hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/BlockListAsLongs.java
* hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/SimulatedFSDataset.java

> 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
>             Fix For: 3.0.0
>         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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