The default partitioner will take the key, make the hash from it, and do a modulo operation to determine the partition it goes to. Some things which might cause it to and up different for different topics: - partition number are not the same (you already checked) - key is not exactly the same, for example one might have a space after the id - the other topic is configured to use another partitioner - the serialiser for the key is different for both topics, since the hash is created based on the bytes of key of the serialised message - all the topics use another partitioner (for example round robin)
On Thu, Jul 28, 2016 at 9:11 PM Jack Huang <jackhu...@mz.com> wrote: > Hi all, > > I have an application where I need to join events from two different > topics. Every event is identified by an id, which is used as the key for > the topic partition. After doing some experiment, I observed that events > will go into different partitions even if the number of partitions for both > topics are the same. I can't find any documentation on this point though. > Does anyone know if this is indeed the case? > > > Thanks, > Jack >
