Hey Tao, This error indicates that a rebalance completed successfully before the consumer could rejoin. Basically it works like this:
1. Consumer 1 joins the group and is assigned member id A 2. Consumer 1's session timeout expires before successfully heartbeating. 3. The group is rebalanced without consumer 1. 4. Consumer 1 eventually sends its heartbeat using the old id A. 5. The coordinator rejects the heartbeat with UNKNOWN_MEMBER_ID. So most likely what has happened is that the consumer has taken longer than the session timeout to handle a batch of records. In 0.10, we will have an option max.poll.records to limit the amount of data returned from each call to poll() so that you can better predict processing time. -Jason On Mon, Mar 14, 2016 at 7:04 AM, tao xiao <xiaotao...@gmail.com> wrote: > Hi team, > > I have about 10 consumers using the same consumer group connecting to > Kafka. Occasional I can see UNKNOWN_MEMBER_ID assigned to some of the > consumers. I want to under what situation this would happen? > > I use Kafka version 0.9.0.1 >
