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https://issues.apache.org/jira/browse/HDFS-9144?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15003043#comment-15003043
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Haohui Mai commented on HDFS-9144:
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A pretty large patch. Can you explain what you're trying to achieve here? Some
more questions:
* What is the purpose of having multiple inheritances on {{FileHanlde}},
{{FileHandleImpl}}, {{CancelHandle}}, {{CancelHandleImpl}}?
* Why having multi-inheritance?
* What is the principle of life cycle management here? Why changing pointers to
shared_ptr in {{RemoteBlockReader}}? It's deliberately left as normal pointer
as continuations do not own the stream, but the {{State}} object own it. What
is the purpose of copying the callback handlers?
* What is cancelable? Is a request cancelable or a stream cancelable? Why
{{AsyncStream}} inherits {{Cancelable}}.
The patch contains many unnecessary changes and can be separated into several
patches. There are refactors in NN, DN, various changes from here and there. It
needs to be separated, reviewed and applied independently.
> 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,
> HDFS-9144.HDFS-8707.002.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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