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From "Joe Pallas (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HDFS-7680) Support dataset-specific choice of short circuit implementation
Date Tue, 27 Jan 2015 00:27:35 GMT

     [ https://issues.apache.org/jira/browse/HDFS-7680?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Joe Pallas updated HDFS-7680:
-----------------------------
    Description: 
As described in HDFS-5194, the current support for short circuit reading is tightly coupled
to the default Dataset implementation.  Since alternative implementations of the FsDatasetSpi
may use a different short circuit pathway, there needs to be a way for the client to acquire
the right kind of BlockReader.

Reviewing some considerations:
Today, there is only one dataset per datanode (with multiple volumes).  Is that likely to
change?
Can there be multiple datanodes local to a client? (definition of "local" might depend on
dataset implementation)
Is it okay to assume that the client and datanode share configuration?  More broadly, how
should the client discover the appropriate short-circuit implementation?


  was:
As described in HDFS-5194, the current support for short circuit reading is tightly coupled
to the default Dataset implementation.  Since alternative implementations of the FsDatasetSpi
may use a different short circuit pathway, there needs to be a way for the client to acquire
the right kind of BlockReader.

Reviewing some considerations:
Today, there is only one dataset per datanode (with multiple volumes).  Is that likely to
change?
Can there be multiple datanodes local to a client?
Is it okay to assume that the client and datanode share configuration?  More broadly, how
should the client discover the appropriate short-circuit implementation?



> Support dataset-specific choice of short circuit implementation
> ---------------------------------------------------------------
>
>                 Key: HDFS-7680
>                 URL: https://issues.apache.org/jira/browse/HDFS-7680
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: datanode, dfsclient, hdfs-client
>    Affects Versions: 3.0.0
>            Reporter: Joe Pallas
>            Assignee: Joe Pallas
>
> As described in HDFS-5194, the current support for short circuit reading is tightly coupled
to the default Dataset implementation.  Since alternative implementations of the FsDatasetSpi
may use a different short circuit pathway, there needs to be a way for the client to acquire
the right kind of BlockReader.
> Reviewing some considerations:
> Today, there is only one dataset per datanode (with multiple volumes).  Is that likely
to change?
> Can there be multiple datanodes local to a client? (definition of "local" might depend
on dataset implementation)
> Is it okay to assume that the client and datanode share configuration?  More broadly,
how should the client discover the appropriate short-circuit implementation?



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