[HADOOP-829] Separate the datanode contents that is written to the fsimage vs the contents used in over-the-wire communication

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 0.10.0
• Assignee: Dhruba Borthakur
• Reporter: Dhruba Borthakur
• Created: 15/Dec/06 05:10
• Updated: 08/Jul/09 16:42
• Resolved: 18/Dec/06 20:59

Description

In the existing implementation, the Namenode has a data structure called DatanodeDescriptor. It is used to serialize contents of the Datanode while writing it to the fsimage. The same serialization method is used to send a Datanode object to the Datanode and/or the Client. This introduces the shortcoming that one cannot introduce non-persistent fields in the DatanodeDescriptor.

One solution is to separate out the following two functionality into two separate classes:
1. The fields from a Datanode that are part of the ClientProtocol and/or DatanodeProcotol.
2. The fields from a Datanode that are stored in the fsImage.