Good writeup, Jimmy (was away for a few days due to an event in my family)
 
Some quick questions - Has there been any thoughts on the plan to use 
HBASE-5394. Are we going to make the hbase protocols (like HRegionInterface) 
protobuf aware?

In Hadoop, I have seen the following:
1. In HDFS, the protocol definitions are not changed (like 
org.apache.hadoop.hdfs.protocol.ClientProtocol). Instead there are translators 
that are defined that implement the mapping of protobuf datastructures to 
application-level datastructures and vice versa (for example, have a look at 
ClientNamenodeProtocolTranslatorPB and 
ClientNamenodeProtocolServerSideTranslatorPB in the package 
org.apache.hadoop.hdfs.protocolPB).
2. In Yarn (MRV2), all protocol definitions are written in PB
 
Since the base RPC still uses writables for payload encoding, a translation 
happens when the protobuf objects are sent/received (as an example look at 
org.apache.hadoop.ipc.ProtobufRpcEngine; classes RpcRequestWritable and 
RpcResponseWritable).
 
What does the HBase community think about the above?


On Feb 13, 2012, at 1:02 PM, Jimmy Xiang wrote:

> I posted the proposal on wiki:
> 
> http://wiki.apache.org/hadoop/Hbase/HBaseWireCompatibility
> 
> Thanks,
> Jimmy
> 
> On Mon, Feb 13, 2012 at 11:03 AM, Ted Yu <[email protected]> wrote:
> 
>> Can you post on wiki ?
>> 
>> Attachment stripped.
>> 
>> On Mon, Feb 13, 2012 at 11:01 AM, Jimmy Xiang <[email protected]> wrote:
>> 
>>> Hello,
>>> 
>>> As HBase installation base is getting bigger, we are ready to work on the
>>> wire compatibility issue.
>>> The goal is to make HBase easier for operators to upgrade, while it is
>>> also easier for developers to
>>> enhance, re-architect if necessary.
>>> 
>>> The attached is a proposal we came up.  We'd like to start with two
>> phases:
>>> 
>>> Phase 1: Compatibility between client applications and HBase clusters
>>> Phase 2: HBase cluster rolling upgrade within same major version
>>> 
>>> Could you please review?
>>> 
>>> Thanks,
>>> Jimmy
>>> 
>> 

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