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From "Bob Hansen (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-9144) Refactor libhdfs into stateful/ephemeral objects
Date Thu, 22 Oct 2015 14:00:35 GMT

    [ https://issues.apache.org/jira/browse/HDFS-9144?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14969191#comment-14969191
] 

Bob Hansen commented on HDFS-9144:
----------------------------------

Thanks for the feedback; [~wheat9]: you are correct, the RpcEngine is owned by the NNConnection.

By "familiar", I mean an easy path for those who are used to POSIX file semantics: open a
file, sequential reads, seeks, close a file.  We will, of course, also support parallel asynchronous
positional reads, but I think we want a nice clean interface for POSIX-y semantics.

Let's break the work down into smaller pieces.  I started with abstracting out the NN connection
in the attached patch.  I will work on abstracting the DN connection next.

> Refactor libhdfs into stateful/ephemeral objects
> ------------------------------------------------
>
>                 Key: HDFS-9144
>                 URL: https://issues.apache.org/jira/browse/HDFS-9144
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: hdfs-client
>    Affects Versions: HDFS-8707
>            Reporter: Bob Hansen
>            Assignee: Bob Hansen
>         Attachments: HDFS-9144.HDFS-8707.001.patch
>
>
> In discussion for other efforts, we decided that we should separate several concerns:
> * A posix-like FileSystem/FileHandle object (stream-based, positional reads)
> * An ephemeral ReadOperation object that holds the state for reads-in-progress, which
consumes
> * An immutable FileInfo object which holds the block map and file size (and other metadata
about the file that we assume will not change over the life of the file)



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