Technically this is the guarantee we provide--at least once delivery. It is very expensive to completely eliminate this possibility in the general case as you need to co-ordinate any state changes the consumer makes with committing the offset that marks the position. But we have improved the common cases for normal rebalancing so if you are using trunk the only time this would happen is when there is a hard crash of a process.
-Jay On Wed, May 16, 2012 at 2:41 AM, navneet sharma <navneetsharma0...@gmail.com> wrote: > Hi, > > I tried a scenario wherein: > 1) i had 1 producer and 3 consumers subscribed for a topic - "cartTopic", > all in same group. > 2) Now, when everything is executing, i introduced another consumer for the > same topic and in the same group. So, overall there are 4 consumers. > 3) Ofcourse, it triggered re-balancing. > > But then final result is that few messages are duplicated. > In my example run, producer sent 800,000 records, but consumer received > 801,448 records. > I am using log4j to generate the output file. > > Is there any reasons for duplicacy? > > Thanks, > Navneet Sharma
