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https://issues.apache.org/jira/browse/HADOOP-11199?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14180210#comment-14180210
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Ray Chiang commented on HADOOP-11199:
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I don't recall the specifics of any example offhand, but I do recall running
into an MR/YARN property situation which looked something like this:
1) Newer property overrides the older property, but the older property is still
the default behavior
2) Both properties are defined in the corresponding .xml file. Empty/null
equivalency is exploited in that both are documented, but one is "undefined"
which prevents the newer one from overriding the older one.
Sadly, I can't remember the exact property offhand, but I would expect it's in
one of mapred-default.xml or yarn-default.xml since I haven't looked at any
others.
I'm fine with having value null/value empty/value fully defined as three
definite states--I just don't know what side effects there would be until all
the code is updated.
Right now, I see 31 properties in yarn-default.xml and 16 in mapred-default.xml
that are empty/null.
> Configuration should be able to set empty value for property
> ------------------------------------------------------------
>
> Key: HADOOP-11199
> URL: https://issues.apache.org/jira/browse/HADOOP-11199
> Project: Hadoop Common
> Issue Type: Bug
> Components: conf
> Reporter: Wangda Tan
> Attachments: HADOOP-11199-01.patch
>
>
> Currently in hadoop.common.conf.Configuration, when you specify a XML like
> this:
> {code}
> <configuration>
> <property>
> <name>conf.name</name>
> <value></value>
> </property>
> </configuration>
> {code}
> When you trying to get the conf.name, the returned value is null instead of
> an empty string.
> Test code for this,
> {code}
> import java.io.ByteArrayInputStream;
> import org.apache.hadoop.conf.Configuration;
> public class HadoopConfigurationEmptyTest {
> public static void main(String[] args) {
> Configuration conf = new Configuration(false);
> ByteArrayInputStream bais =
> new ByteArrayInputStream(("<configuration><property>"
> + "<name>conf.name</name>" + "<value></value>"
> + "</property></configuration>").getBytes());
> conf.addResource(bais);
> System.out.println(conf.get("conf.name"));
> }
> }
> {code}
> Does this intentionally or a behavior should be fixed?
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