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From "Vinay (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-9870) Mixed configurations for JVM -Xmx in hadoop command
Date Wed, 20 Nov 2013 04:57:34 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-9870?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13827338#comment-13827338
] 

Vinay commented on HADOOP-9870:
-------------------------------

AFAIK, java process, processes its commandline VM args sequentially. If the same VM argument
is set multiple times,it will choose the last one as its value.
Even though hadoop have many -Xmx configurations, it will take the last one in the list. 
User need not confuse about the other JVM argument (-Xmx1000m) as that will help if user didnot
configure anything ( in case HADOOP_CONF_DIR is different and it dont have hadoop-env.sh file).

So I am not seeing any issue here.

> Mixed configurations for JVM -Xmx in hadoop command
> ---------------------------------------------------
>
>                 Key: HADOOP-9870
>                 URL: https://issues.apache.org/jira/browse/HADOOP-9870
>             Project: Hadoop Common
>          Issue Type: Bug
>            Reporter: Wei Yan
>         Attachments: HADOOP-9870.patch, HADOOP-9870.patch, HADOOP-9870.patch
>
>
> When we use hadoop command to launch a class, there are two places setting the -Xmx configuration.
> *1*. The first place is located in file {{hadoop-common-project/hadoop-common/src/main/bin/hadoop}}.
> {code}
> exec "$JAVA" $JAVA_HEAP_MAX $HADOOP_OPTS $CLASS "$@"
> {code}
> Here $JAVA_HEAP_MAX is configured in hadoop-config.sh ({{hadoop-common-project/hadoop-common/src/main/bin/hadoop-config.sh}}).
The default value is "-Xmx1000m".
> *2*. The second place is set with $HADOOP_OPTS in file {{hadoop-common-project/hadoop-common/src/main/bin/hadoop}}.
> {code}
> HADOOP_OPTS="$HADOOP_OPTS $HADOOP_CLIENT_OPTS"
> {code}
> Here $HADOOP_CLIENT_OPTS is set in hadoop-env.sh ({{hadoop-common-project/hadoop-common/src/main/conf/hadoop-env.sh}})
> {code}
> export HADOOP_CLIENT_OPTS="-Xmx512m $HADOOP_CLIENT_OPTS"
> {code}
> Currently the final default java command looks like:
> {code}java -Xmx1000m .... -Xmx512m CLASS_NAME ARGUMENTS"{code}
> And if users also specify the -Xmx in the $HADOOP_CLIENT_OPTS, there will be three -Xmx
configurations. 
> The hadoop setup tutorial only discusses hadoop-env.sh, and it looks that users should
not make any change in hadoop-config.sh.
> We should let hadoop smart to choose the right one before launching the java command,
instead of leaving for jvm to make the decision.



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