Move unsupported ClientProtocol methods to new class

[shvachko]

Original issue 95 created by shvachko on 2015-04-15T18:33:38.000Z:

We should create an abstract class, UnsupportedClientProtocol, as a placeholder for all of the client methods we don't support. This will make NamespaceProcessor and NamespaceAgent more compact, and it will be easier to add the dozens of additional methods introduced in later Hadoop versions.

[shvachko]

Comment #2 originally posted by shvachko on 2015-04-15T18:36:10.000Z:

Attaching patch.

[shvachko]

I reviewed Milan's patch. The idea is good, but we cannot uniformly through IOException for all operations. Some operations are currently implemented as no-op in NamespaceAgent, which allows to run MR jobs. With your implementation jobs will fail. We should keep the dummy implementation for those in NamespaceAgent, but add a log message that says nothing was done. Here is the list of ops that should not throw. Check other operations as well.

• getDelegationToken()
• renewDelegationToken()
• cancelDelegationToken()
• updateBlockForPipeline()
• updatePipeline()
• setSafeMode() is called by mini cluster, check if this make tests fail.

On the server side though, that is in NamespaceProcessor, we want these operations to throw, because we don't want them be called by mistake. And let's make sure the jobs can run after this change.

Formatting: looks like your IDE adds CR/LF. Could you change it to the Linux style, please.

[shvachko]

Also need Apache license in the new file header.

[shvachko]

I think we should drop #95. It is a refactoring, which is merging client and sever logic for unsupported ClientProtocol methods. And I think we should keep them separate. And eventually support everything. Discussed with Milan. Closing as won't fix.