> > 28. On the broker, we typically use Yammer metrics. Only for metrics that > depend on Kafka metric features (e.g., quota), we use the Kafka metric. > Yammer metrics have 4 types: gauge, meter, histogram and timer. meter > calculates a rate, but also exposes an accumulated value. >
I don't see a good reason we should limit ourselves to Yammer metrics on the broker. KafkaMetrics was written to replace Yammer metrics and is used for all new components (clients, streams, connect, etc.) My understanding is that the original goal was to retire Yammer metrics in the broker in favor of KafkaMetrics. We just haven't done so out of backwards compatibility concerns. There are other broker metrics such as group coordinator, transaction state manager, and various socket server metrics already using KafkaMetrics that don't need specific Kafka metric features, so I don't see why we should refrain from using Kafka metrics on the broker unless there are real compatibility concerns or where implementation specifics could lead to confusion when comparing metrics using different implementations. In my opinion we should encourage people to use KafkaMetrics going forward on the broker as well, for two reasons: a) yammer metrics is long deprecated and no longer maintained b) yammer metrics are much less expressive c) we don't have a proper API to expose yammer metrics outside of JMX (MetricsReporter only exposes KafkaMetrics)
