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https://issues.apache.org/jira/browse/HADOOP-4584?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Suresh Srinivas updated HADOOP-4584:
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Attachment: 4584.hbthread.patch
Updated patch for separating heartbeat thread. Methods
{{FSDataset.getCapacity(), FSDataset.getDfsUsed(), FSDataset.getRemaining()}}
use commands such as {{df}} and {{du}} on data directories and does not need to
be synchronized with FSVolumeSet.
Changes are:
* Removed synchronizing {{FSVolumeSet.getCapacity()}} on {{FSVolumeSet}}
* Removed synchronizing {{FSVolumeSet.getRemaining()}} on {{FSVolumeSet}}
* Access to {{FSDataset.getCapacity(), FSDataset.getRemaining(),
FSDataset.getDfsUsed()}} are synchronized
Note if {{df}} operation blocks, the heartbeat thread will be blocked. However
assuming it will be much shorter than 10 minutes and the datanodes will not be
marked dead by namenodes.
> 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.hbthread.patch, 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.
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