Home | About | Sematext search-lucene.com search-hadoop.com
 Search Hadoop and all its subprojects:

Switch to Threaded View
MapReduce, mail # user - One mapper/reducer runs on a single JVM


Copy link to this message
-
One mapper/reducer runs on a single JVM
Lin Ma 2012-11-06, 01:12
Hello Hadoop experts,

I have a question in my mind for a long time. Supposing I am developing M-R
program, and it is Java based (Java UDF, implements mapper or reducer
interface). My question is, in this scenario, whether a mapper or a reducer
is a separate JVM process? E.g. supposing on a machine, there are 4
mappers, they are 4 individual processes? I am also wondering whether the
processes on a single machine will impact each other when each JVM wants to
get more memory to run faster?

thanks in advance,
Lin