Multiple RPC Servers using same object instance
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Key: HADOOP-6469
URL: https://issues.apache.org/jira/browse/HADOOP-6469
Project: Hadoop Common
Issue Type: New Feature
Reporter: Dmytro Molkov
In HDFS-599 we want to be able to run multiple RPC servers on the namenode. One
for DataNodes another for the rest of the protocols.
The problem right now is that checking if the protocol is exposed is done on
the handler side (the NameNode in our case).
In our usecase we want to be able to tell if the request is coming on the
"datanode port" or "the rest port" and based on that throw an exception when
datanodes are accessing the client port and vice versa. Since the JobTracker
has the same abstraction of Clients and Slaves those might later also be split
on to different servers. So creating a solution just inside of the NameNode is
not really an options, especially since we could not come up with one that
would be clean and safe.
The proposal is to have RPC servers have "tags" associated with them in these
cases. Then in the NameNode 2 servers created will have tags "DataNodeServer"
and "ClientAdminServer". Another change is instead of using VersionedProtocol
to check the version and the protocol in the getProtocolVersion method, Classes
that can be used in multiple contexts should implement another interface
(MultiServer?) that will have a checkProtocol? method that receives the name of
the protocol and the Tag associated with the Server that received the request.
This way in the checkProtocol we can specify which Protocols are allowed for
servers tagged with Tag.
What do people think?
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