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From "Daryn Sharp (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-7270) Add congestion signaling capability to DataNode write protocol
Date Mon, 05 Jan 2015 16:43:36 GMT

    [ https://issues.apache.org/jira/browse/HDFS-7270?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14264755#comment-14264755
] 

Daryn Sharp commented on HDFS-7270:
-----------------------------------

Conceptually this appears to be a useful feature.   Could you please elaborate on how you
intend to implement its use in a followup jira?  I'd like to evaluate if your approach will
improve or exasperate current issues in our environment.  How will a DN signal congestion?
 When will it signal congestion?  Ie. In a premature ack since prior ack easily becomes stale?
 What will the client do?  

On a minor note, please avoid the ImmutableList and its Builder usage instead of a primitive
array since it adds little value compared to more boxing and GC overhead.

> Add congestion signaling capability to DataNode write protocol
> --------------------------------------------------------------
>
>                 Key: HDFS-7270
>                 URL: https://issues.apache.org/jira/browse/HDFS-7270
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: datanode
>            Reporter: Haohui Mai
>            Assignee: Haohui Mai
>         Attachments: HDFS-7270.000.patch, HDFS-7270.001.patch, HDFS-7270.002.patch
>
>
> When a client writes to HDFS faster than the disk bandwidth of the DNs, it  saturates
the disk bandwidth and put the DNs unresponsive. The client only backs off by aborting / recovering
the pipeline, which leads to failed writes and unnecessary pipeline recovery.
> This jira proposes to add explicit congestion control mechanisms in the writing pipeline.




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