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https://issues.apache.org/jira/browse/HDFS-5574?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13852068#comment-13852068
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Colin Patrick McCabe commented on HDFS-5574:
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If it's easy, then I would say do {{RemoteBlockReader}} as well, just to avoid
divergence. There are still some people who have to use the old block reader--
for example, if they are using SOCKS sockets.
The main point of the old block reader is that it can operate on sockets that
don't have channels. In the long term, I feel like we could probably wrap
those sockets in something that would provide a channel, or just integrate that
functionality into {{RemoteBlockReader2}}.
Your test doesn't really test what you think. {{DFSInputStream#skip}} is not
necessarily going to call {{BlockReader#skip}}. If you want to play with a
remote block reader directly, you should call the test
{{TestRemoteBlockReader}} or something like that. There is an example in
{{TestBlockTokenWithDFS}}. Also, you should set
{{DFSInputStream#tcpReadsDisabledForTesting}} if you want to make sure you're
really getting a local block reader.
Finally, {{BlockReaderLocal}} lets you skip past the end of the file without
complaining. This behavior is consistent with how
{{FileInputChannel#position}} works. Since the {{DFSInputStream}} knows the
length of the block (reader), it never tries to skip past the end.
> Remove buffer copy in BlockReader.skip
> --------------------------------------
>
> Key: HDFS-5574
> URL: https://issues.apache.org/jira/browse/HDFS-5574
> Project: Hadoop HDFS
> Issue Type: Improvement
> Reporter: Binglin Chang
> Assignee: Binglin Chang
> Priority: Trivial
> Attachments: HDFS-5574.v1.patch, HDFS-5574.v2.patch,
> HDFS-5574.v3.patch
>
>
> BlockReaderLocal.skip and RemoteBlockReader.skip uses a temp buffer to read
> data to this buffer, it is not necessary.
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