[KAFKA-13359] Round Robin Kafka Producer Routes to only half the partitions when even number of partitions

• Type: Bug
• Status: Open
• Priority: Minor
• Resolution: Unresolved
• Affects Version/s: 2.7.0, 3.0.0
• Component/s: producer
• Assignee: Unassigned
• Reporter: David G
• Created: 07/Oct/21 09:58
• Updated: 07/Oct/21 10:20

Description

When you have 1 message per batch, in the round robin Partitioner. The messages go only to half the partitions beacuse it always skips 1 partition. This works out for odd number of partitions because skipping 1 will mean all partitions get a hit eventually, but with an even number half the partitions never get selected.

 

So if you have partitions 1, 2, 3, 4 

Message 1: Partion 1

Message 2: Partion 3

Message 3: Partion 1 ... so on. [ Here 2 and 4 are never selected]

 

If you have partitions 1, 2, 3

Message 1: Partion 1

Message 2: Partion 3

Message 3: Partion 2 .. so on