Map tasks run in parallel spawned JVMs, so are isolated from one another at runtime. Use of static functions shouldn't affect you generally.
Default Map I/O is single-threaded. If you plan to use multiple-threads, use MultiThreadedMapper for proper thread-safety. On Thu, Aug 29, 2013 at 8:15 PM, Pavan Sudheendra <[email protected]> wrote: > No, I had written a huge Map Reduce program which talks with hbase and does > a lot of computing using it as a source as well as sink.. One of my > colleague saw my code and saw that I had used a lot of static function > instead of making use of proper OOP concepts.. He was telling me that it > shouldn't be the way I should go about doing it.. But my code works fine.. > So, was wondering will I face any problem in the future because of this.. > That's all. > > Regards, > Pavan > > On Aug 29, 2013 8:11 PM, "Adam Muise" <[email protected]> wrote: >> >> 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. >> >> Hortonworks Virtual Sandbox >> >> Hadoop: Disruptive Possibilities by Jeff Needham >> >> 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. -- Harsh J
