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https://issues.apache.org/jira/browse/HADOOP-11223?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15795391#comment-15795391
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Colin P. McCabe commented on HADOOP-11223:
------------------------------------------

If the real problem is reloading all those XML files all the time, why not 
change that behavior in Hadoop 3.x?  At the very least, we could have some kind 
of mapping between classpath and default configuration values, and only 
actually load the XML files when we saw a new classpath which might cause us to 
load some different files.

> Offer a read-only conf alternative to new Configuration()
> ---------------------------------------------------------
>
>                 Key: HADOOP-11223
>                 URL: https://issues.apache.org/jira/browse/HADOOP-11223
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: conf
>            Reporter: Gopal V
>            Assignee: Varun Saxena
>              Labels: Performance
>         Attachments: HADOOP-11223.001.patch
>
>
> new Configuration() is called from several static blocks across Hadoop.
> This is incredibly inefficient, since each one of those involves primarily 
> XML parsing at a point where the JIT won't be triggered & interpreter mode is 
> essentially forced on the JVM.
> The alternate solution would be to offer a {{Configuration::getDefault()}} 
> alternative which disallows any modifications.
> At the very least, such a method would need to be called from 
> # org.apache.hadoop.io.nativeio.NativeIO::<clinit>()
> # org.apache.hadoop.security.SecurityUtil::<clinit>()
> # org.apache.hadoop.yarn.factory.providers.RecordFactoryProvider::<clinit>



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