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From "Wei Yan (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-9870) Mixed configurations for JVM -Xmx in hadoop command
Date Wed, 20 Nov 2013 05:25:24 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-9870?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13827354#comment-13827354
] 

Wei Yan commented on HADOOP-9870:
---------------------------------

[~vinayrpet]. As I said above, I haven't found any documents that said the jvm would pick
the last one. Correct me if I'm wrong here. So this patch wants to make this clear, instead
of letting jvm make the decision to choose which as the jvm setting.

> 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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