Launcher is implemented as a Java application and sometimes I'd like to apply Java options.
One situation I have met is the time I try to attach debugger to Launcher.
Launcher is launched from bin/spark-class but there is no room to apply Java options.
```
build_command() {
"$RUNNER" -Xmx128m -cp "$LAUNCH_CLASSPATH" org.apache.spark.launcher.Main "$"
printf "%d\0" $?
}
```
Considering that it's not so many times to apply Java options to Launcher, one compromise would just modify spark-class by user like as follows.
```
build_command() {
"$RUNNER" -Xmx128m $SPARK_LAUNCHER_OPTS -cp "$LAUNCH_CLASSPATH" org.apache.spark.launcher.Main "$"
printf "%d\0" $?
}
```
But it doesn't work when any text related to Java options is output to standard output because whole output is used as command-string for spark-shell and spark-submit in current implementation.
One example is jdwp. When apply agentlib option to use jdwp for debug, we will get output like as follows.
```
Listening for transport dt_socket at address: 9876
```
The output shown above is not a command-string so spark-submit and spark-shell will fail.
To enable Java options for Launcher, we need treat command-string and others.
I changed launcher/Main.java and bin/spark-class to print separator-character and treat it.
## How was this patch tested?
Tested manually using Spark Shell with / without LAUNCHER_JAVA_OPTIONS like as follows.
```
SPARK_LAUNCHER_OPTS="-agentlib:jdwp=transport=dt_socket,suspend=y,address=localhost:9876,server=y" bin/spark-shell
```
Closes#25265 from sarutak/add-spark-launcher-opts.
Authored-by: Kousuke Saruta <sarutak@oss.nttdata.com>
Signed-off-by: Marcelo Vanzin <vanzin@cloudera.com>
121f9338ce