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https://issues.apache.org/jira/browse/HDFS-4820?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13662381#comment-13662381
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Siddharth Seth commented on HDFS-4820:
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bq. Without defaults in the XML, this code will need to hard-code the mapping
somewhere. We'll have to remember to cover all cases like this.
Agree, this would be a little more complicated, but can likely be solved with
config code which is more complicated than a simple get("config key", default).
bq. This may be a bigger concern for compatibility. Configuration is annotated
public/stable, and I've seen a lot of tutorials with sample code that
instantiates a new instance and expects it to be fully populated with the keys
from *-default.xml. For full compatibility, I suppose we'd need to update not
only our own Configuration#get calls to enforce the defaults, but also
guarantee that if a client creates a new instance, they get the same values
that used to be provided in the XML. Again, this probably would involve some
kind of hard-coding during static initialization.
This does sound problematic. Should users really care if the configuration
object is populated with a lot of defaults (not all defaults unless we've been
extremely careful about putting all keys into *-default.xml).
In terms of the values being used by client being the same across versions -
changing defaults within a major release will likely be incompatible,
especially for user facing keys - and we should avoid this.
> Remove hdfs-default.xml
> -----------------------
>
> Key: HDFS-4820
> URL: https://issues.apache.org/jira/browse/HDFS-4820
> Project: Hadoop HDFS
> Issue Type: Improvement
> Affects Versions: 2.0.4-alpha
> Reporter: Siddharth Seth
>
> Similar to YARN-673, which contains additional details.
> There's separate jiras for YARN, MR and HDFS so enough people take a look.
> Looking for reasons for these files to exist, other than the ones mentioned
> in YARN-673, or a good reason to keep the files.
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