[jira] [Commented] (HADOOP-9870) Mixed configurations for JVM -Xmx in hadoop command

["Kai Zheng (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HADOOP-9870?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13738972#comment-13738972 ] 

Kai Zheng commented on HADOOP-9870:
-----------------------------------

Similar issue was also found for HDFS related services, ref. HDFS-5087.

It looks like we have two approaches to set JAVA heap max, by configuring JAVA_HEAP_MAX or adding -Xmx option directly in related *_OPTS. We might avoid using the both and the conflict.

Also looked at other components like YARN. To be consistent, we could fix this by I would suggest:
1. Add variable HADOOP_CLIENT_HEAPSIZE, and user can set it either in hadoop-env.sh or hadoop-config.sh;
2. In appropriate script, check HADOOP_CLIENT_HEAPSIZE and set the value to JAVA_HEAP_MAX if any.

                
> 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
>
> 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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