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https://issues.apache.org/jira/browse/HDFS-7270?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14307749#comment-14307749
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Haohui Mai commented on HDFS-7270:
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It should be a compatible change. The upgrade path is the following:
1. Upgrade the cluster with the feature turned off.
2. Turn on the feature in the configuration.
The new client is able to talk to the old client since in the wire protocol,
the old clients will report that they do not support ECN.
> 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, HDFS-7270.003.patch, HDFS-7270.004.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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