heartbeatPayload property
Builds the application data piggy-backed on every Heartbeat (e.g. a
resource-metrics snapshot), consumed hub-side by
NodeGateway.onHeartbeat.
Evaluated on each beat. Keep it cheap: a slow or throwing builder does not delay or suppress the beat — liveness never depends on telemetry — but the beat then carries no payload.
Implementation
final Future<Map<String, dynamic>> Function()? heartbeatPayload;