heartbeat(payload) {
		if (!this.available) {
			this.available = true;
			this.offlineSince = null;
		}

		if (payload.cpu != null) {
			this.cpu = payload.cpu;
			this.cpuSeq = payload.cpuSeq || 1;
		}

		this.lastHeartbeatTime = Math.round(process.uptime());
	}
Update heartbeat properties

@param {any} payload
@memberof Node