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https://issues.apache.org/jira/browse/HADOOP-9194?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13597602#comment-13597602
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Luke Lu commented on HADOOP-9194:
---------------------------------
After HADOOP-9380, RPC will look like this:
{code}
request ::= <connection-header> (<request-payload-length-in32>
<request-payload>)+
connection-header ::= 'hrpc' <version-int8> <auth-int8>
<serialization-type-int8>
response ::= (<response-payload-length-int32> <response-payload>)+
{code}
How about we add the service-class byte after the version byte? so the
connection-header length is 8 :)
> RPC Support for QoS
> -------------------
>
> Key: HADOOP-9194
> URL: https://issues.apache.org/jira/browse/HADOOP-9194
> Project: Hadoop Common
> Issue Type: New Feature
> Components: ipc
> Affects Versions: 2.0.2-alpha
> Reporter: Luke Lu
>
> One of the next frontiers of Hadoop performance is QoS (Quality of Service).
> We need QoS support to fight the inevitable "buffer bloat" (including various
> queues, which are probably necessary for throughput) in our software stack.
> This is important for mixed workload with different latency and throughput
> requirements (e.g. OLTP vs OLAP, batch and even compaction I/O) against the
> same DFS.
> Any potential bottleneck will need to be managed by QoS mechanisms, starting
> with RPC.
> How about adding a one byte DS (differentiated services) field (a la the
> 6-bit DS field in IP header) in the RPC header to facilitate the QoS
> mechanisms (in separate JIRAs)? The byte at a fixed offset (how about 0?) of
> the header is helpful for implementing high performance QoS mechanisms in
> switches (software or hardware) and servers with minimum decoding effort.
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