[jira] Updated: (HDFS-941) Datanode xceiver protocol should allow reuse of a connection

["bc Wong (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HDFS-941?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

bc Wong updated HDFS-941:
-------------------------

    Attachment: HDFS-941-1.patch

Attaching a patch, which:
* In {{DFSInputStream}}, stores the last socket and the owner ({{BlockReader}}) of that socket.
* If the owner did read till EOS, then it'll consider reusing that socket.
* It's a cache of size 1, but easy to extend to _n_. However, size of 1 makes sense for now because:
* The DN ({{DataXceiver}}) no longer closes the client connection after every op. It optimistically expects the next op, with a very low timeout value. It closes the connection only on EOS or timeout.

Note that the HDFS-941-1.patch depends on the HDFS-1001 patch.

> Datanode xceiver protocol should allow reuse of a connection
> ------------------------------------------------------------
>
>                 Key: HDFS-941
>                 URL: https://issues.apache.org/jira/browse/HDFS-941
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: data-node, hdfs client
>    Affects Versions: 0.22.0
>            Reporter: Todd Lipcon
>         Attachments: HDFS-941-1.patch
>
>
> Right now each connection into the datanode xceiver only processes one operation.
> In the case that an operation leaves the stream in a well-defined state (eg a client reads to the end of a block successfully) the same connection could be reused for a second operation. This should improve random read performance significantly.

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