[jira] Commented: (HDFS-724) Pipeline close hangs if one of the datanode is not responsive.

["Hairong Kuang (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HDFS-724?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12774382#action_12774382 ] 

Hairong Kuang commented on HDFS-724:
------------------------------------

If a datanode really becomes non-responsive, the dfs client is able to detect the problem.

The issue here is that the test simulates a non-responsive block receiver. While the block receiver is blocked, the packet responder is still alive and sends heartbeats back periodically. So the client still thinks the pipeline is working good.

The solution:
1. packet responder does not send heartbeats. instead, turn on the tcp/ip level heartbeats by setting the socket "keepalive" to be true.
2. dfs client does not receive acks until there is one outstanding packet.

> 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
>            Reporter: Tsz Wo (Nicholas), SZE
>         Attachments: h724_20091021.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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