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https://issues.apache.org/jira/browse/HDFS-101?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12792248#action_12792248
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Todd Lipcon commented on HDFS-101:
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Looking at the patch, I'm confused by the logic in handleMirrorOutError. It
seems to me that the if statement there checking for a non-empty clientName
should actually be checking whether it's the last node in the pipeline. If it's
the first node in the pipeline, shouldn't it propagate the error backward just
as if it received the error while receiving an ack?
> DFS write pipeline : DFSClient sometimes does not detect second datanode
> failure
> ---------------------------------------------------------------------------------
>
> Key: HDFS-101
> URL: https://issues.apache.org/jira/browse/HDFS-101
> Project: Hadoop HDFS
> Issue Type: Bug
> Affects Versions: 0.20.1
> Reporter: Raghu Angadi
> Assignee: Hairong Kuang
> Priority: Blocker
> Fix For: 0.21.0
>
> Attachments: detectDownDN-0.20.patch, detectDownDN.patch,
> detectDownDN1.patch, hdfs-101.tar.gz
>
>
> When the first datanode's write to second datanode fails or times out
> DFSClient ends up marking first datanode as the bad one and removes it from
> the pipeline. Similar problem exists on DataNode as well and it is fixed in
> HADOOP-3339. From HADOOP-3339 :
> "The main issue is that BlockReceiver thread (and DataStreamer in the case of
> DFSClient) interrupt() the 'responder' thread. But interrupting is a pretty
> coarse control. We don't know what state the responder is in and interrupting
> has different effects depending on responder state. To fix this properly we
> need to redesign how we handle these interactions."
> When the first datanode closes its socket from DFSClient, DFSClient should
> properly read all the data left in the socket.. Also, DataNode's closing of
> the socket should not result in a TCP reset, otherwise I think DFSClient will
> not be able to read from the socket.
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