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From "stack (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-101) DFS write pipeline : DFSClient sometimes does not detect second datanode failure
Date Wed, 04 May 2011 05:06:03 GMT

    [ https://issues.apache.org/jira/browse/HDFS-101?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13028607#comment-13028607
] 

stack commented on HDFS-101:
----------------------------

Do we know what issue fixed this failing test?  We should backport it to branch-0.20-append
branch.  Thanks.

> 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
>          Components: data-node
>    Affects Versions: 0.20.1, 0.20-append
>            Reporter: Raghu Angadi
>            Assignee: Hairong Kuang
>            Priority: Blocker
>             Fix For: 0.20.2, 0.20-append, 0.21.0
>
>         Attachments: HDFS-101_20-append.patch, detectDownDN-0.20.patch, detectDownDN1-0.20.patch,
detectDownDN2.patch, detectDownDN3-0.20-yahoo.patch, detectDownDN3-0.20.patch, detectDownDN3.patch,
hdfs-101-branch-0.20-append-cdh3.txt, hdfs-101.tar.gz, pipelineHeartbeat.patch, pipelineHeartbeat_yahoo.patch
>
>
> 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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