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

["Wei Yan (JIRA)" <ji...@apache.org>]

Wei Yan created HADOOP-9870:
-------------------------------

             Summary: 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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