[HDFS-4273] Fix some issue in DFSInputstream

• Type: Bug
• Status: Resolved
• Priority: Minor
• Resolution: Won't Fix
• Affects Version/s: 2.0.2-alpha
• Target Version/s: 2.0.3-alpha
• Assignee: Binglin Chang
• Reporter: Binglin Chang
• Created: 05/Dec/12 15:03
• Updated: 22/May/15 07:49
• Resolved: 22/May/15 07:49

Description

Following issues in DFSInputStream are addressed in this jira:
1. read may not retry enough in some cases cause early failure
Assume the following call logic

 
readWithStrategy()
  -> blockSeekTo()
  -> readBuffer()
     -> reader.doRead()
     -> seekToNewSource() add currentNode to deadnode, wish to get a different datanode
        -> blockSeekTo()
           -> chooseDataNode()
              -> block missing, clear deadNodes and pick the currentNode again
        seekToNewSource() return false
     readBuffer() re-throw the exception quit loop
readWithStrategy() got the exception,  and may fail the read call before tried MaxBlockAcquireFailures.

2. In multi-threaded scenario(like hbase), DFSInputStream.failures has race condition, it is cleared to 0 when it is still used by other thread. So it is possible that some read thread may never quit. Change failures to local variable solve this issue.

3. If local datanode is added to deadNodes, it will not be removed from deadNodes if DN is back alive. We need a way to remove local datanode from deadNodes when the local datanode is become live.

Issue Links

• is related to: HDFS-6022 Moving deadNodes from being thread local. Improving dead datanode handling in DFSClient