Kafka Heartbeat Response Wire Format v3 — Binary Protocol Layout

What is Heartbeat?

Classic-protocol consumers send this on a fixed interval to prove liveness to the group coordinator. Missing a heartbeat within session.timeout.ms kicks the member and triggers a rebalance, usually because consumers spend too long in poll() processing, starving the heartbeat thread.

Schema
{
  "ThrottleTimeMs": int32,
  "ErrorCode": int16
}

Example
{
  "ThrottleTimeMs": 0,
  "ErrorCode": 0
}