Jonathan Ellithorpe created HADOOP-12574:
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Summary: Multiple Xmx Parameters to Java Process
Key: HADOOP-12574
URL: https://issues.apache.org/jira/browse/HADOOP-12574
Project: Hadoop Common
Issue Type: Bug
Affects Versions: 2.7.1
Reporter: Jonathan Ellithorpe
When launching hadoop, the setting of environment variable HADOOP_HEAPMAX
results in multiple Xmx parameters being passed to the java application
launcher. This is because a default Xmx setting included in the
HADOOP_CLIENT_OPTS in etc/hadoop/hadoop-env.sh, line 61:
# The following applies to multiple commands (fs, dfs, fsck, distcp etc)
export HADOOP_CLIENT_OPTS="-Xmx512m $HADOOP_CLIENT_OPTS"
is merged into the variable HADOOP_OPTS in bin/hadoop, line 160:
# Always respect HADOOP_OPTS and HADOOP_CLIENT_OPTS
HADOOP_OPTS="$HADOOP_OPTS $HADOOP_CLIENT_OPTS"
Orthogonally, the HADOOP_HEAPMAX environment variable triggers the setting of
JAVA_HEAP_MAX in hadoop-config.sh, line 192:
# check envvars which might override default args
if [ "$HADOOP_HEAPSIZE" != "" ]; then
#echo "run with heapsize $HADOOP_HEAPSIZE"
JAVA_HEAP_MAX="-Xmx""$HADOOP_HEAPSIZE""m"
#echo $JAVA_HEAP_MAX
fi
Which is ultimately passed to the java application launcher in bin/hadoop, line
166:
exec "$JAVA" $JAVA_HEAP_MAX $HADOOP_OPTS $CLASS "$@"
The result: two Xmx settings passed to the Java application launcher. Which one
is respected depends on the JVM, but for HotSpot the rightmost setting is
respected, and so the HADOOP_HEAPMAX environment variable has no effect and the
default setting in HADOOP_CLIENT_OPTS wins.
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