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https://issues.apache.org/jira/browse/HDFS-7966?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14588688#comment-14588688
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stack commented on HDFS-7966:
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bq. The code path is completely separated so it should be few risks in terms of
destabilizing the trunk.
My concern is not so much destabilization. My concern is a bunch of new code
that may never get used.
Reviewing the patches so far, it seems like you fellas are working it out as
you go. Nothing wrong with that. It just seems like something better done in a
branch than in mainline.
The justification for this work is a little nebulous. It has it that "[DTP on
HTTP/2] ...should simplify the implementation of both HDFS clients and
servers." Apart from the fact that DTP is but a severe subset, the 'easy' part,
of what an alternative client/server would have to implement, what if HTTP/2
complicates rather than simplifies new clients and servers? Better to figure
this, and 'fit criteria' that prove it simplifies, on a branch I'd say.
Also, why would folks move to using this new transport? Will it be more
performant than current DTP? (I'd guess not... given HTTP/2 does a bunch of
'extras' and going by the PoC done over in HBase) When complete, we might have
a bunch of new code that is slower than what is currently there and that folks
are wary to try given it is 'new'. This state of affairs could go on such that
the code is never exercised.
I am suggesting a branch because there you work out implementation, perf
characteristics, and answers to any questions such as the sample posed above
and come merge time, you will have a more solid story to tell.
> New Data Transfer Protocol via HTTP/2
> -------------------------------------
>
> Key: HDFS-7966
> URL: https://issues.apache.org/jira/browse/HDFS-7966
> Project: Hadoop HDFS
> Issue Type: New Feature
> Reporter: Haohui Mai
> Assignee: Qianqian Shi
> Labels: gsoc, gsoc2015, mentor
> Attachments: GSoC2015_Proposal.pdf
>
>
> The current Data Transfer Protocol (DTP) implements a rich set of features
> that span across multiple layers, including:
> * Connection pooling and authentication (session layer)
> * Encryption (presentation layer)
> * Data writing pipeline (application layer)
> All these features are HDFS-specific and defined by implementation. As a
> result it requires non-trivial amount of work to implement HDFS clients and
> servers.
> This jira explores to delegate the responsibilities of the session and
> presentation layers to the HTTP/2 protocol. Particularly, HTTP/2 handles
> connection multiplexing, QoS, authentication and encryption, reducing the
> scope of DTP to the application layer only. By leveraging the existing HTTP/2
> library, it should simplify the implementation of both HDFS clients and
> servers.
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