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https://issues.apache.org/jira/browse/HADOOP-6949?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12999245#comment-12999245
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Konstantin Shvachko commented on HADOOP-6949:
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- I recommend looking for subclasses of VersionedProtocol rather than search.
You can see that most of the protocols you listed implement VersionedProtocol,
except for two AvroRpcEngine and WritableRpcEngine, which implement RpcEngine.
Avro has its own serialization object, afaiu, so we don't need to change
version for the latter two.
- I think it is fine to change only ipc.Server#CURRENT_VERSION, as Hairong
sugested, which is the VersionedProtocol version, rather than all subclasses,
as it will provide incompatibility for all of them at once.
- As I said in my
[comment|https://issues.apache.org/jira/browse/HDFS-1583?focusedCommentId=12981404&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-12981404]
in HDFS-1583, Java does not support heterogeneous arrays, see
[ArrayStoreException|http://download.oracle.com/javase/6/docs/api/java/lang/ArrayStoreException.html]
for the reference. So we don't need to support such generic semantic. We can
assume the array is strictly homogeneous.
- Yes we need to support only arrays of Writables (and of primitive types).
- NULL values should be supported.
- My opinion this is important optimization to be included in 0.22. If people
have doubts I can start a vote on general. Lmk.
> Reduces RPC packet size for primitive arrays, especially long[], which is
> used at block reporting
> -------------------------------------------------------------------------------------------------
>
> Key: HADOOP-6949
> URL: https://issues.apache.org/jira/browse/HADOOP-6949
> Project: Hadoop Common
> Issue Type: Improvement
> Components: io
> Reporter: Navis
> Assignee: Matt Foley
> Fix For: 0.23.0
>
> Attachments: ObjectWritable.diff, arrayprim.patch, arrayprim_v4.patch
>
> Original Estimate: 10m
> Remaining Estimate: 10m
>
> Current implementation of oah.io.ObjectWritable marshals primitive array
> types as general object array ; array type string + array length + (element
> type string + value)*n
> It would not be needed to specify each element types for primitive arrays.
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