Mappers don't communicate with each other in traditional MapReduce. If you need something more MPI-ish then look to MPI over YARN or write your own YARN app.
If you need multi-threading within the mapper then it is up to you as the java developer to make it thread safe. Use the concurrent libraries like anything else and Bob's your uncle. Having overly-complicated mappers can be difficult to manage however and it kind of misses the mark for MapReduce problems. Maybe if you expand on your use case a bit someone here can provide specific advice. On Thu, Aug 29, 2013 at 10:33 AM, Pavan Sudheendra <[email protected]>wrote: > Hi all, > > Is hadoop thread safe? Do mappers make use of threads in any chance? A > little bit of information on the way they execute in parallel would help me > out. Thanks. > > Regards, > Pavan > -- * * * * *Adam Muise* Solution Engineer *Hortonworks* [email protected] 416-417-4037 Hortonworks - Develops, Distributes and Supports Enterprise Apache Hadoop.<http://hortonworks.com/> Hortonworks Virtual Sandbox <http://hortonworks.com/sandbox> Hadoop: Disruptive Possibilities by Jeff Needham<http://hortonworks.com/resources/?did=72&cat=1> -- CONFIDENTIALITY NOTICE NOTICE: This message is intended for the use of the individual or entity to which it is addressed and may contain information that is confidential, privileged and exempt from disclosure under applicable law. If the reader of this message is not the intended recipient, you are hereby notified that any printing, copying, dissemination, distribution, disclosure or forwarding of this communication is strictly prohibited. If you have received this communication in error, please contact the sender immediately and delete it from your system. Thank You.
