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From "Haohui Mai (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-9117) Config file reader / options classes for libhdfs++
Date Tue, 17 Nov 2015 17:27:11 GMT

    [ https://issues.apache.org/jira/browse/HDFS-9117?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15009074#comment-15009074

Haohui Mai commented on HDFS-9117:

bq. We will also need a non-static method to load another batch of settings on top of currently
loaded ones.

There is no need to support this. It's possible to make the configuration fully immutable.

bq. I don't see how it reduces the API exposure; we need to define what types we support etiher
way, and continue supporting them either way.

Not much differences from a linker's prospective, huge differences from human's prospective
as it requires (1) two declarations for each type in the header file, and (2) mostly identical
implementations to support getting the default value of the types.

The configuration needs to support integer, boolean, string, timeout, bytes, URI, vector of
int, and vector of string, just to name a few.

bq.  With the templated getter, there is no way to tell whether or not config.get<int>("")
is implemented.

You can do it via (1) explicitly instantiating the templates, and (2) having a generic template
which only contains a {{static_assert}}.

> Config file reader / options classes for libhdfs++
> --------------------------------------------------
>                 Key: HDFS-9117
>                 URL: https://issues.apache.org/jira/browse/HDFS-9117
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: hdfs-client
>    Affects Versions: HDFS-8707
>            Reporter: Bob Hansen
>            Assignee: Bob Hansen
>         Attachments: HDFS-9117.HDFS-8707.001.patch, HDFS-9117.HDFS-8707.002.patch, HDFS-9117.HDFS-8707.003.patch,
HDFS-9117.HDFS-8707.004.patch, HDFS-9117.HDFS-8707.005.patch, HDFS-9117.HDFS-8707.006.patch,
HDFS-9117.HDFS-8707.008.patch, HDFS-9117.HDFS-8707.009.patch, HDFS-9117.HDFS-8707.010.patch,
HDFS-9117.HDFS-8707.011.patch, HDFS-9117.HDFS-8707.012.patch, HDFS-9117.HDFS-8707.013.patch,
HDFS-9117.HDFS-8707.014.patch, HDFS-9117.HDFS-8707.015.patch, HDFS-9117.HDFS-9288.007.patch
> For environmental compatability with HDFS installations, libhdfs++ should be able to
read the configurations from Hadoop XML files and behave in line with the Java implementation.
> Most notably, machine names and ports should be readable from Hadoop XML configuration
> Similarly, an internal Options architecture for libhdfs++ should be developed to efficiently
transport the configuration information within the system.

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