As with all software systems, observability into their health is critical.
With many deployment platforms (be them custom-built or open-source), tasks like restarting a misbehaving server in a cluster are completely automated. With Kafka, monitoring systems have no definitive source of truth to gauge when a server/client has been started. They are left to either use arbitrary Kafka-specific metrics as a heuristic or the JVM RuntimeMXBean's StartTime, which is not exactly indicative of when the application itself started
It would be useful to have a metric exposing when the kafka server has started.