[HDFS-10548] Remove the long deprecated BlockReaderRemote

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 3.0.0-alpha1
• Component/s: hdfs
• Target Version/s: 3.0.0-alpha1
• Hadoop Flags: Incompatible change, Reviewed
• Release Note: This removes the configuration property {{dfs.client.use.legacy.blockreader}}, since the legacy remote block reader class has been removed from the codebase.
• Assignee: Kai Zheng
• Reporter: Kai Zheng
• Created: 20/Jun/16 01:42
• Updated: 12/Jul/16 23:22
• Resolved: 02/Jul/16 04:26

Description

To lessen the maintain burden like raised in HDFS-8901, suggest we remove BlockReaderRemote class that's deprecated very long time ago.

From BlockReaderRemote header:

• @deprecated this is an old implementation that is being left around
• in case any issues spring up with the new
  Unknown macro: {@link BlockReaderRemote2}
• implementation.
• It will be removed in the next release.

From BlockReaderRemote2 class header:

• This is a new implementation introduced in Hadoop 0.23 which
• is more efficient and simpler than the older BlockReader
• implementation. It should be renamed to BlockReaderRemote
• once we are confident in it.

So even further, after getting rid of the old class, we could rename as the comment suggested: BlockReaderRemote2 => BlockReaderRemote.