Hi, Thanks for the follow up.
By "classic" I meant the protocol implemented by the SyncGroup/JoinGroup API [1]. It's a general group protocol that is still fully supported in Kraft, and at this time has no intention of being deprecated. It's called "classic" to distinguish it from the newer KIP-848 [2] ConsumerGroupHeartbeat API and the share group protocol used in KIP-932 [3]. It is my understanding that these other protocols are _not_ a synchronizing barrier in the same way the "classic" protocol is. Hope this helps, Greg [1] https://github.com/apache/kafka/blob/adb033211497e539725366960e1013a4638de59f/group-coordinator/src/main/java/org/apache/kafka/coordinator/group/classic/ClassicGroup.java [2] https://cwiki.apache.org/confluence/display/KAFKA/KIP-848%3A+The+Next+Generation+of+the+Consumer+Rebalance+Protocol [3] https://cwiki.apache.org/confluence/display/KAFKA/KIP-932%3A+Queues+for+Kafka On Tue, Jan 21, 2025 at 4:41 PM Chain Head <mrchainh...@gmail.com> wrote: > Thanks. > > By "classic" you mean pre-KRaft consensus? What is the "current" Kafka > Group protocol? > > Best regards. > > On Tue, Jan 21, 2025 at 9:55 PM Greg Harris <greg.har...@aiven.io.invalid> > wrote: > > > Hi, > > > > Yes you are correct. The "classic" Kafka Group Protocol is a > synchronizing > > barrier for all members. > > All JoinGroup member responses are returned after all JoinGroup member > > requests are received. > > > > Thanks, > > Greg > > > > On Tue, Jan 21, 2025 at 7:10 AM Chain Head <mrchainh...@gmail.com> > wrote: > > > > > Assume that three consumers of a certain group want to connect to a > > broker > > > for a topic with 3 partitions. After the FindCoordinator API is done, > the > > > consumers send JoinGroup. Since the broker cannot know in advance how > > many > > > consumers are expected to join, it waits > > group.initial.rebalance.delay.ms > > > before starting a rebalance. > > > > > > Therefore, does this mean the JoinGroup API response of each request is > > > "held" until the waiting period is over? > > > > > > Best regards. > > > > > >
