checkRemoteNodes() {
		if (this.opts.disableHeartbeatChecks) return;

		const now = Math.round(process.uptime());
		this.registry.nodes.toArray().forEach(node => {
			if (node.local || !node.available) return;
			if (!node.lastHeartbeatTime) {
				// Not received the first heartbeat yet
				node.lastHeartbeatTime = now;
				return;
			}

			if (now - node.lastHeartbeatTime > this.opts.heartbeatTimeout) {
				this.logger.warn(`Heartbeat is not received from '${node.id}' node.`);
				this.registry.nodes.disconnected(node.id, true);
			}
		});
	}
Check all registered remote nodes are available.