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B) If we instead model the quotas on a per-topic basis, provisioned quota can be split equally among all the partitions of a topic. For example: If a topic T has 8 partitions and total configured write throughput of 8MBps, each partition gets 1Mbps. If a broker hosts 3 leader partitions for T, then that topic is allowed 3MBps on that broker regardless of the partitions that traffic is directed to. In terms of quota distribution, this is the most elegant model. However, since there can be multiple producers/consumers of a topic, a single misbehaving client can cause multiple clients to get throttled which is undesirable behavior. This is why we have chosen to model quotas on a per-user basis. Since a user can consume from/produce to any number of topic-partitions, it is difficult to track accurately a users quota usage across the entire cluster. This would require some sort of a gossip mechanism we don't currently have. This is why we choose to model quota distribution a per-broker basis.

Quota Actions

A) Immediately return an error: This is the simplest possible option. However, this requires clients to implement some sort of a back off mechanism since retrying immediately will likely make things worse.

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