Hi Ismael, I think this issue comes up when people write software that automatically creates partition reassignments to balance the cluster. Cruise Control is one example; Confluent also has some software that does this. If there is already a reassignment that is going on for some partition and the software tries to create a new reassignment for that partition, the software may inadvertently change the replication factor.
In general, I think some people find it surprising that reassignment can change the replication factor of a partition. When we outlined the reassignment API in KIP-455 we maintained the ability to do this, since the old ZK-based API had always been able to do it. But this was a bit controversial. Maybe it would have been more intuitive to preserve replication factor by default unless the user explicitly stated that they wanted to change it. So in a sense, you could view this as a fix for KIP-455 :) (in my opinion, at least) best, Colin On Wed, Sep 7, 2022, at 07:07, Ismael Juma wrote: > Thanks for the KIP. Can we explain a bit more why this is an important use > case to address? For example, do we have concrete examples of people > running into this? The way the KIP is written, it sounds like a potential > problem but no information is given on whether it's a real problem in > practice. > > Ismael > > On Thu, Jul 28, 2022 at 2:00 AM Stanislav Kozlovski > <stanis...@confluent.io.invalid> wrote: > >> Hey all, >> >> I'd like to start a discussion on a proposal to help API users from >> inadvertently increasing the replication factor of a topic through >> the alter partition reassignments API. The KIP describes two fairly >> easy-to-hit race conditions in which this can happen. >> >> The KIP itself is pretty simple, yet has a couple of alternatives that can >> help solve the same problem. I would appreciate thoughts from the community >> on how you think we should proceed, and whether the proposal makes sense in >> the first place. >> >> Thanks! >> >> KIP: >> >> https://cwiki.apache.org/confluence/display/KAFKA/KIP-860%3A+Add+client-provided+option+to+guard+against+replication+factor+change+during+partition+reassignments >> JIRA: https://issues.apache.org/jira/browse/KAFKA-14121 >> >> -- >> Best, >> Stanislav >>
