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From "Xiaoyu Yao (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-11939) Ozone : add read/write random access to Chunks of a key
Date Fri, 16 Jun 2017 15:44:00 GMT

    [ https://issues.apache.org/jira/browse/HDFS-11939?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16052051#comment-16052051

Xiaoyu Yao commented on HDFS-11939:

[~vagarychen], thanks for working on this. I have a generic question about implementing FileChannel
for ChunkInputStream/ChunkOutputStream. Have we consider implementing a simpler interface
like org.apache.hadoop.fs.Seekable/PositionedRead from FSInputStream/FSOutputStream on top
of existing ChunkInputStream/ChunkOutputStream? This way, we can avoid many duplicate code
between  ChunkInputStream/ChunkOutputStream and the new ChunkInputChannel/ChunkOutputChannel.

> Ozone : add read/write random access to Chunks of a key
> -------------------------------------------------------
>                 Key: HDFS-11939
>                 URL: https://issues.apache.org/jira/browse/HDFS-11939
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>            Reporter: Chen Liang
>            Assignee: Chen Liang
>         Attachments: HDFS-11939-HDFS-7240.001.patch, HDFS-11939-HDFS-7240.002.patch,
HDFS-11939-HDFS-7240.003.patch, HDFS-11939-HDFS-7240.004.patch
> In Ozone, the value of a key is a sequence of container chunks. Currently, the only way
to read/write the chunks is by using ChunkInputStream and ChunkOutputStream. However, by the
nature of streams, these classes are currently implemented to only allow sequential read/write.

> Ideally we would like to support random access of the chunks. For example, we want to
be able to seek to a specific offset and read/write some data. This will be critical for key
range read/write feature, and potentially important for supporting parallel read/write.
> This JIRA tracks adding support by implementing FileChannel class on top Chunks.

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