title: Kafka group rebalance not getting message on partition
body: <p>I have a Kafka consumer that consumes large amounts of data from a Kafka topic with 9 partitions. When the application starts consumes all messages until it gets a partition-eof from all assigned partitions, or there are no more messages.</p>
  <p>When the first instance starts it therefore consumes from all 9 partitions until the EOF. There's around 1000 messages a second being produced and it consumes until EOF without problem.</p>
  <p>I then start a second instance. Kafka takes partitions 0 to 4 and assigns them to the second instance. I see this happen as I've got a <code>PartitionAssignedHandler</code> in place which gets called with the assignments. I then enter my &quot;consume until partition EOF&quot; loop. The strange thing is that when I start consuming messages I don't see any on one of the partitions (partition 2 in my case). All the other partitions return messages. The <code>Assigment</code> property on the consumer shows that partition 2 is assigned to me, but no data arrives.</p>
  <p>Eventually, after around 10 minutes, data does start to arrive on partition 2 and everything works as expected.</p>
  <p>However, this seems strange to me. Why is one of the partitions not returning messages for such a long period? I don't have odd settings in place to configure the consumer. Is it just the case that Kafka doesn't promise timely delivery, just eventual delivery, and therefore this behavior is expected?</p>