[
https://issues.apache.org/jira/browse/HDFS-1235?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Todd Lipcon resolved HDFS-1235.
-------------------------------
Resolution: Duplicate
Fixed by HDFS-630
> Namenode returning the same Datanode to client, due to infrequent heartbeat
> ---------------------------------------------------------------------------
>
> Key: HDFS-1235
> URL: https://issues.apache.org/jira/browse/HDFS-1235
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: name-node
> Reporter: Thanh Do
>
> This bug has been reported.
> Basically since datanode's hearbeat messages are infrequent (~ every 10
> minutes),
> NameNode always gives the client the same datanode even if the datanode is
> dead.
>
> We want to point out that the client wait 6 seconds before retrying,
> which could be considered long and useless retries in this scenario,
> because in 6 secs, the namenode hasn't declared the datanode dead.
> Overall this happens when a datanode is dead during the first phase of the
> pipeline (file setups).
> If a datanode is dead during the second phase (byte transfer), the DFSClient
> still
> could proceed with the other surviving datanodes (which is consistent with
> what
> Hadoop books always say -- the write should proceed if at least we have one
> good
> datanode). But unfortunately this specification is not true during the first
> phase of the
> pipeline. Overall we suggest that the namenode take into consideration the
> client's
> view of unreachable datanodes. That is, if a client says that it cannot
> reach DN-X,
> then the namenode might give the client another node other than X (but the
> namenode
> does not have to declare N dead).
> This bug was found by our Failure Testing Service framework:
> http://www.eecs.berkeley.edu/Pubs/TechRpts/2010/EECS-2010-98.html
> For questions, please email us: Thanh Do (than...@cs.wisc.edu) and
> Haryadi Gunawi (hary...@eecs.berkeley.edu)
--
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.
