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https://issues.apache.org/jira/browse/HDFS-724?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12789930#action_12789930
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Hairong Kuang commented on HDFS-724:
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Let me provide more information about this patch:
1. heart beat is an empty packet with a sequence number of -1;
2. At the client side, heart beat packets are not queued in any of the queues
because there is no need to resend a heartbeat if there is an error sending
heartbeats.
2. At the datanode side, heartbeats are queued in the ack queue. A datanode
treats a heartbeat the same as a regular data packet. The ack of a heartbeat
packet is the same as a regular data packet as well. To distinguish a heartbeat
from an end-of-block packet, receivePacket returns -1 when receiving an
end-of-block packet.
Dhruba, please feel free to reach me if you need more explanation. I need this
patch to be committed before I committing HDFS-101.
> Pipeline close hangs if one of the datanode is not responsive.
> --------------------------------------------------------------
>
> Key: HDFS-724
> URL: https://issues.apache.org/jira/browse/HDFS-724
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: data-node, hdfs client
> Affects Versions: 0.21.0
> Reporter: Tsz Wo (Nicholas), SZE
> Assignee: Hairong Kuang
> Priority: Blocker
> Fix For: 0.21.0
>
> Attachments: h724_20091021.patch, pipelineHeartbeat.patch,
> pipelineHeartbeat1.patch, pipelineHeartbeat2.patch
>
>
> In the new pipeline design, pipeline close is implemented by sending an
> additional empty packet. If one of the datanode does not response to this
> empty packet, the pipeline hangs. It seems that there is no timeout.
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