Hi everybody, I have a little problem with cassandra-all jar file : when i want to write back the result of the MapReduce in DB, he says me that the SpecificRecord class (Hector API) is not found... I have already check this dependency and it's ok. Do I have to use the Cassandra API or it's a technical problem ?
Thanks 2011/5/27 Laurent Hatier <[email protected]> > Of couurse !!! It's logical. > Thank you John. > > 2011/5/27 John Armstrong <[email protected]> > >> On Fri, 27 May 2011 13:52:04 +0200, Laurent Hatier >> <[email protected]> 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. >> > > > > -- > Laurent HATIER > Étudiant en 2e année du Cycle Ingénieur à l'EISTI > -- Laurent HATIER Étudiant en 2e année du Cycle Ingénieur à l'EISTI
