Hi Alyssa, Thanks for the questions.
RE AH2: You could also unregister a controller via the `kafka-cluster unregister-controller` command I am proposing in this KIP. Invoking either CLI command being introduced in this KIP with the wrong controller id can result in an operator accidentally unregistering a controller which is still running (has not been decommissioned). In this case, the controller needs to re-register since it is still part of the kafka cluster. RE AH3: Let me fix this sentence. I mean "The intention for unregistration is for it to occur after the operator decommissions a controller node. This means the node is no longer part of the kafka cluster, and the controller process associated with this node is not expected to come back." The unregister CLI command will return something to the user based on the UnregsiterControllerResponse. Best, Kevin Wu On Fri, Apr 3, 2026 at 3:27 PM Alyssa Huang via dev <[email protected]> wrote: > Few more questions actually > > AH1 > Thanks, I was mainly trying to understand if dynamic reconfiguration offers > an incomplete downscaling UX without this KIP. Seems like that's the case. > I also missed the scenario with observer controllers so thanks for > clarifying that part. > > AH2 > > > The registration manager of an unregistered controller should attempt to > > re-register with the active controller. This is to prevent accidental > > unregistrations. > > I'm not sure if this makes sense to me, what would be an accidental > unregistration? Is the only trigger for unregistration the new > remove-controller command you're adding? > > AH3 > > > The intention for unregistration is for it to occur after the operator > > decommissions a node which will no longer be part of the kafka cluster, > and > > is not expected to return. > > Why isn't the command expected to return? > > Thanks! > > On Fri, Apr 3, 2026 at 12:15 PM Alyssa Huang <[email protected]> wrote: > > > Thanks for the KIP Kevin! > > > > AH1 > > > >> This means a stale controller registration from a controller that no > >> longer exists can block feature upgrades. > > > > > > And dynamic reconfiguration (specifically RemoveVoter) can cause stale > > controller registrations? Meaning anyone who has used RemoveVoter to > > permanently downsize their controller quorum would eventually need to > > unregister the controller to unblock future feature upgrades? > > > > Best, > > Alyssa > > > > On Fri, Apr 3, 2026 at 11:30 AM Kevin Wu <[email protected]> wrote: > > > >> Hi all, > >> > >> I would like to start a discussion on KIP-1312: Support unregistering > >> controllers. Below is the KIP link. > >> > >> > >> > https://cwiki.apache.org/confluence/display/KAFKA/KIP-1312%3A+Support+unregistering+controllers > >> > >> Thanks, > >> Kevin Wu > >> > > >
