KIP-583 — add tag "partition" to BrokerTopicMetrics so as to observe the partition metrics on the same broker

Discussion MetricsBroker

KIP-583 proposes adding a `partition=<id>` tag to the `BrokerTopicMetrics` JMX metrics (e.g. `BytesInPerSec`, `BytesOutPerSec`) so operators can observe traffic at partition granularity. Currently, partition-level metrics are aggregated at the topic level, making it impossible to observe intra-topic traffic imbalance caused by custom partitioners or hot-key distributions.

Details