Lucas Bradstreet created KAFKA-12896: ----------------------------------------
Summary: Group rebalance loop caused by repeated group leader JoinGroups Key: KAFKA-12896 URL: https://issues.apache.org/jira/browse/KAFKA-12896 Project: Kafka Issue Type: Bug Components: clients Affects Versions: 2.6.0 Reporter: Lucas Bradstreet We encountered a strange case of a rebalance loop with the "cooperative-sticky" assignor. The logs show the following for several hours: {{Apr 7, 2021 @ 03:58:36.040 [GroupCoordinator 7]: Stabilized group mygroup generation 19830137 (__consumer_offsets-7)}} {{Apr 7, 2021 @ 03:58:35.992 [GroupCoordinator 7]: Preparing to rebalance group mygroup in state PreparingRebalance with old generation 19830136 (__consumer_offsets-7) (reason: Updating metadata for member mygroup-1-7ad27e07-3784-4588-97e1-d796a74d4ecc during CompletingRebalance)}} {{Apr 7, 2021 @ 03:58:35.988 [GroupCoordinator 7]: Stabilized group mygroup generation 19830136 (__consumer_offsets-7)}} {{Apr 7, 2021 @ 03:58:35.972 [GroupCoordinator 7]: Preparing to rebalance group mygroup in state PreparingRebalance with old generation 19830135 (__consumer_offsets-7) (reason: Updating metadata for member mygroup during CompletingRebalance)}} {{Apr 7, 2021 @ 03:58:35.965 [GroupCoordinator 7]: Stabilized group mygroup generation 19830135 (__consumer_offsets-7)}} {{Apr 7, 2021 @ 03:58:35.953 [GroupCoordinator 7]: Preparing to rebalance group mygroup in state PreparingRebalance with old generation 19830134 (__consumer_offsets-7) (reason: Updating metadata for member mygroup-7ad27e07-3784-4588-97e1-d796a74d4ecc during CompletingRebalance)}} {{Apr 7, 2021 @ 03:58:35.941 [GroupCoordinator 7]: Stabilized group mygroup generation 19830134 (__consumer_offsets-7)}} {{Apr 7, 2021 @ 03:58:35.926 [GroupCoordinator 7]: Preparing to rebalance group mygroup in state PreparingRebalance with old generation 19830133 (__consumer_offsets-7) (reason: Updating metadata for member mygroup during CompletingRebalance)}} Every single time, it was the same member that triggered the JoinGroup and it was always the leader of the group.{{}} The leader has the privilege of being able to trigger a rebalance by sending `JoinGroup` even if its subscription metadata has not changed. But why would it do so? It is possible that this is due to the same issue or a similar bug to https://issues.apache.org/jira/browse/KAFKA-12890. -- This message was sent by Atlassian Jira (v8.3.4#803005)