[
https://issues.apache.org/jira/browse/HADOOP-4584?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12676396#action_12676396
]
Raghu Angadi commented on HADOOP-4584:
--------------------------------------
Just moving heartbeat to a different thread is useful by itself. My quote from
4th comment above :
bq. "I think this approach might work ok for now. It makes sure the data node
is not marked dead. But this should be considered mostly a work around. We
should note the fundamental problem still remains (a little less lethal). e.g.
a) new blocks are not reported, b) no new blocks can be written during this
time c) (not sure) not blocks can be read? etc. "
If that is what everyone wants then it is ok. But we will continue to see
problems with datanodes with lot of blocks. My impression is that it is about
time we fix the fundamental problem with the scan in block reports.
> Slow generation of blockReport at DataNode causes delay of sending heartbeat
> to NameNode
> ----------------------------------------------------------------------------------------
>
> Key: HADOOP-4584
> URL: https://issues.apache.org/jira/browse/HADOOP-4584
> Project: Hadoop Core
> Issue Type: Bug
> Components: dfs
> Reporter: Hairong Kuang
> Assignee: Suresh Srinivas
> Fix For: 0.20.0
>
> Attachments: 4584.patch, 4584.patch, 4584.patch, 4584.patch,
> 4584.patch, 4584.patch
>
>
> sometimes due to disk or some other problems, datanode takes minutes or tens
> of minutes to generate a block report. It causes the datanode not able to
> send heartbeat to NameNode every 3 seconds. In the worst case, it makes
> NameNode to detect a lost heartbeat and wrongly decide that the datanode is
> dead.
> It would be nice to have two threads instead. One thread is for scanning data
> directories and generating block report, and executes the requests sent by
> NameNode; Another thread is for sending heartbeats, block reports, and
> picking up the requests from NameNode. By having these two threads, the
> sending of heartbeats will not get delayed by any slow block report or slow
> execution of NameNode requests.
--
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.
