[jira] [Commented] (YARN-2625) Problems with CLASSPATH in Job Submission REST API

["Doug Haigh (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/YARN-2625?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14264577#comment-14264577 ] 

Doug Haigh commented on YARN-2625:
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I am not using MR. I am writing my own AppMaster which requires knowing the path to the Hadoop ecosystem's CLASSPATH. Unless you expect Hadoop to be rewritten in something other than JAVA, most AppMaster jars written in Java will be required to know the CLASSPATH of the Hadoop ecosystem they are expected to run under. If you want to add a REST API to specifically get the CLASSPATH of the Hadoop ecosystem a Java AppMaster will run under, that is fine with me.

> Problems with CLASSPATH in Job Submission REST API
> --------------------------------------------------
>
>                 Key: YARN-2625
>                 URL: https://issues.apache.org/jira/browse/YARN-2625
>             Project: Hadoop YARN
>          Issue Type: Bug
>          Components: api
>    Affects Versions: 2.5.1
>            Reporter: Doug Haigh
>
> There are a couple of issues I have found specifying the CLASSPATH environment variable using the REST API.
> 1) In the Java client, the CLASSPATH environment is usually made up of either the value of the yarn.application.classpath in yarn-site.xml value or the default YARN classpath value as defined by YarnConfiguration.DEFAULT_YARN_CROSS_PLATFORM_APPLICATION_CLASSPATH. REST API consumers have no method of telling the resource manager to use the default unless they hardcode the default value themselves. If the default ever changes, the code would need to change. 
> 2) If any environment variables are used in the CLASSPATH environment 'value' field, they are evaluated when the values are NULL resulting in bad values in the CLASSPATH. For example, if I had hardcoded the CLASSPATH value to the default of "$HADOOP_CONF_DIR, $HADOOP_COMMON_HOME/share/hadoop/common/*, $HADOOP_COMMON_HOME/share/hadoop/common/lib/*, $HADOOP_HDFS_HOME/share/hadoop/hdfs/*, $HADOOP_HDFS_HOME/share/hadoop/hdfs/lib/*, $HADOOP_YARN_HOME/share/hadoop/yarn/*, $HADOOP_YARN_HOME/share/hadoop/yarn/lib/*" the classpath passed to the application master is ":/share/hadoop/common/*:/share/hadoop/common/lib/*:/share/hadoop/hdfs/*:/share/hadoop/hdfs/lib/*:/share/hadoop/yarn/*:/share/hadoop/yarn/lib/*"
> These two problems require REST API consumers to always have the fully resolved path defined in the yarn.application.classpath value. If the property is missing or contains environment varaibles, the application created by the REST API will fail due to the CLASSPATH being incorrect.



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