On Fri, 27 May 2011 13:52:04 +0200, Laurent Hatier <laurent.hat...@gmail.com> wrote: > I'm a newbie with Hadoop/MapReduce. I've a problem with hadoop. I set some > variables in the run function but when Map running, he can't get the value > of theses variables... > If anyone knows the solution :)
By the "run function" do you mean the main method that launches the map/reduce job? It's no surprise that the mappers (and reducers) won't know those variables, because they run as completely separate tasks. If you're computing something in the setup method for use in the mappers or reducers you'll have to pass that information along somehow. If it's a String (or something that can easily be made into a String, like an int) you can set it as a property in the job's Configuration. For more complicated data you'll have to serialize it to a file, place the file into the distributed cache, and then deserialize the data within the mapper or reducer's setup method. Of course, if the computation is less complicated/time consuming than the deserialization process, you may as well just recompute the data in each mapper or reducer.
