How to debug hadoop mapreduce jobs from eclipse?

Question

I\'m running hadoop in a single-machine, local-only setup, and I\'m looking for a nice, painless way to debug mappers and reducers in eclipse. Eclipse has no probl

Answer 1

Make changes in /bin/hadoop (hadoop-env.sh) script. Check to see what command has been fired. If the command is jar, then only add remote debug configuration.

if [ "$COMMAND" = "jar" ] ; then
  exec "$JAVA" -Xdebug -Xrunjdwp:transport=dt_socket,server=y,address=8999 $JAVA_HEAP_MAX $HADOOP_OPTS $CLASS "$@"
else
  exec "$JAVA" $JAVA_HEAP_MAX $HADOOP_OPTS $CLASS "$@"
fi