[HDFS-4866] Protocol buffer support cannot compile under C

• Type: Bug
• Status: Closed
• Priority: Blocker
• Resolution: Fixed
• Affects Version/s: 2.1.0-beta, 3.0.0-alpha1
• Fix Version/s: 2.1.0-beta
• Component/s: namenode
• Target Version/s: 2.1.0-beta
• Hadoop Flags: Incompatible change, Reviewed

Release Note

The Protocol Buffers definition of the inter-namenode protocol required a change for compatibility with compiled C clients. This is a backwards-incompatible change. A namenode prior to this change will not be able to communicate with a namenode after this change.

• Assignee: Arpit Agarwal
• Reporter: Ralph Castain
• Created: 29/May/13 21:43
• Updated: 12/May/16 18:18
• Resolved: 15/Jun/13 04:24

Description

When compiling Hadoop's .proto descriptions for use in C, an error occurs because one of the RPC's in NamenodeProtocol.proto is named "register". This name is a reserved word in languages such as C. When using the Java and C++ languages, the name is hidden inside a class and therefore doesn't cause an error. Unfortunately, that is not the case in non-class languages such as C.

Note: generating the C translation of the .proto files requires installation of the protobuf-c package from google:

http://code.google.com/p/protobuf-c/

Issue Links

• is related to: HDFS-4909 Avoid protocol buffer RPC namespace clashes