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https://issues.apache.org/jira/browse/HDFS-2181?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13119907#comment-13119907
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Sanjay Radia commented on HDFS-2181:
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Yes Todd, you got it right. However I was struck a little bit by your order and
that you didn't mention the key item A below.
Hence I re-order your items and add (A). Also see my next comment which
explains how I plan to proceed.
* A. Separate all the datatypes used for wire protocol (called R23 at this
time) into package protocolR23Compatible. These data types are not exposed to
DFSClient or to the NN. DFSClient and NN use their native HDFS types (which
currently reside in o.a.h.hdfs.protocol.) This is done as follows:
** [Your item 3:] For each of the current types (eg LocatedBlocks, etc), copy
them into a protocolR23Compatible package. For each of these classes, add a
static method to convert to/from the generic type in the .protocol package
* B. Create 2 translator classes: ClientXXProtocolTranslator and
ClientXXProtocolServerSideTranslator. These translate from to and from wire
types R23 to the builtin types of HDFS. (ie mostly what you label as item 4)
* C. NN and DFSCLient are not exposed to proxies or to R23 data types:
** [Your item 1] Move the construction of RPC proxies and wire objects into a
"client side translator" class.
** [Your item 2] Pass a new ServerSideTranslator implementation to the
RPC.getServer calls. This ServerSideTranslator translates from wire types back
to the generic protocol types.
If we want to add new protocol serialization (such as PB or Avro) we would add
a new package similar to protocolR23Compatible. I have added a placeholder for
PB. We can also support multiple protocols very easily and pick the right one
based on SS (one critical piece is missing for this - I will file the jira).
> Seperate HDFS wire protocol data types
> --------------------------------------
>
> Key: HDFS-2181
> URL: https://issues.apache.org/jira/browse/HDFS-2181
> Project: Hadoop HDFS
> Issue Type: Improvement
> Reporter: Sanjay Radia
> Assignee: Sanjay Radia
> Attachments: separateDataType1.patch, separateDataType10.patch,
> separateDataType11.patch, separateDataType12.patch, separateDataType13.patch,
> separateDataType14.patch, separateDataType2.patch, separateDataType6.patch,
> separateDataType7.patch, separateDataType8.patch, separateDataType9.patch
>
>
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