[jira] [Commented] (HDFS-9700) DFSClient and DFSOutputStream do not respect TCP_NODELAY config in two spots

["Masatake Iwasaki (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HDFS-9700?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15126245#comment-15126245 ] 

Masatake Iwasaki commented on HDFS-9700:
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Both of {{DFSClient#connectToDN}} and {{DataStreamer#createSocketForPipeline}} should not use {{CommonConfigurationKeysPublic.IPC_CLIENT_TCPNODELAY_KEY}}.

Though I prefer always setting TCP_NODELAY, we should run some benchmark like TestDFSIo to see the effect before change the default behavior.

Adding configuration key such as HdfsClientConfigKeys.DFS_CLIENT_SOCKET_TCP_NODELAY might be conservative option to retain existing behaviour and change the default value later. (You can see HDFS-8829 and HDFS-9259 as example for the fix.)

> DFSClient and DFSOutputStream do not respect TCP_NODELAY config in two spots
> ----------------------------------------------------------------------------
>
>                 Key: HDFS-9700
>                 URL: https://issues.apache.org/jira/browse/HDFS-9700
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: hdfs-client
>    Affects Versions: 2.7.1, 2.6.3
>            Reporter: Gary Helmling
>            Assignee: Gary Helmling
>         Attachments: HDFS-9700-v1.patch, HDFS-9700_branch-2.7.patch
>
>
> In {{DFSClient.connectToDN()}} and {{DFSOutputStream.createSocketForPipeline()}}, we never call {{setTcpNoDelay()}} on the constructed socket before sending.  In both cases, we should respect the value of ipc.client.tcpnodelay in the configuration.
> While this applies whether security is enabled or not, it seems to have a bigger impact on latency when security is enabled.



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