Kafka BrokerHeartbeat Request Wire Format v0 — Binary Protocol Layout

What is BrokerHeartbeat?

Each broker sends this periodically to the KRaft controller to prove liveness and report metadata replication progress. A broker that stops heartbeating gets fenced and its leadership migrated away. The highestMetadataOffset tells the controller how caught up the broker is before unfencing after a restart.

Schema
{
  "BrokerId": int32,
  "BrokerEpoch": int64,
  "CurrentMetadataOffset": int64,
  "WantFence": bool,
  "WantShutDown": bool
}

Example
{
  "BrokerId": 1,
  "BrokerEpoch": 12,
  "CurrentMetadataOffset": 150382,
  "WantFence": true,
  "WantShutDown": true
}