Next.js App Router生产环境API无法返回MQTT更新数据求助

我用Next.js App Router开发的页面，通过路由API获取MQTT数据。开发环境（npm run dev）里请求api/realtimeLocation接口能返回最新的MQTT数据，但生产环境中接口始终返回初始数据，没法拿到更新后的数据，找不到问题原因。

路由文件：app/api/realtimeLocation/route.ts #

import mqttSubscriber from './mqtt-subscriber'

export async function GET(req: any, res: any) {
   const { data } = mqttSubscriber
   let validateData = data ? JSON.parse(data) : null
   try {
      return Response.json({
         status: 'OK',
         data: validateData
      })
   } catch (err) {
      console.error('Something wrong happen')
   }
}

MQTT订阅文件：mqtt-subscriber.js #

import * as mqtt from 'mqtt'

const client = mqtt.connect(`mqtt://${process.env.NEXT_PUBLIC_IP_MQTT}:1883`, {
   username: 'my-user',
   password: 'my-password',
})
// subscribe
client.on('connect', () => {
   const topic = 'fms/liveLocations'
   // subscrive
   client.subscribe(topic, err => {
      if (err) {
         console.log(err)
      } else {
         console.log(`Subscribe to topic: ${topic}`)
      }
   })
})
client.on('error', err => console.log('MQTT Error: ', err))
const receivedData = { data: null }
client.on('message', (receivedTopic, message) => {
   receivedData.data = message.toString()
})

export default receivedData

问题原因及解决方案 #

核心原因 #

Next.js生产环境会对API路由进行静态优化或代码隔离，开发环境下代码热重载且运行在单个进程，MQTT连接和数据能持续共享；但生产环境中API路由可能被打包成无状态函数，模块初始化逻辑无法在服务器生命周期内持续生效，导致无法共享实时更新的MQTT数据。

解决方法 #

1. 实现MQTT客户端单例模式（推荐）

确保整个服务器生命周期内只有一个MQTT连接实例，所有请求共享该实例的实时数据：

import * as mqtt from 'mqtt'

// 全局单例变量
let mqttClient = null;
let receivedData = { data: null };

function initMQTTClient() {
  if (mqttClient) return; // 已初始化直接返回

  mqttClient = mqtt.connect(`mqtt://${process.env.NEXT_PUBLIC_IP_MQTT}:1883`, {
    username: 'my-user',
    password: 'my-password',
  });

  mqttClient.on('connect', () => {
    const topic = 'fms/liveLocations';
    mqttClient.subscribe(topic, err => {
      if (err) {
        console.log(err);
      } else {
        console.log(`Subscribe to topic: ${topic}`);
      }
    });
  });

  mqttClient.on('error', err => console.log('MQTT Error: ', err));
  mqttClient.on('close', () => {
    console.log('MQTT连接断开，正在重连...');
    mqttClient = null;
    initMQTTClient();
  });

  mqttClient.on('message', (receivedTopic, message) => {
    receivedData.data = message.toString();
  });
}

// 服务器启动时初始化连接
initMQTTClient();

export default receivedData;

2. 强制API路由动态执行

在路由文件顶部添加配置，禁用静态优化，确保每次请求都执行路由逻辑：

import mqttSubscriber from './mqtt-subscriber'

export const dynamic = 'force-dynamic'; // 强制动态执行，避免静态缓存

export async function GET(req: any, res: any) {
   const { data } = mqttSubscriber
   let validateData = data ? JSON.parse(data) : null
   try {
      return Response.json({
         status: 'OK',
         data: validateData
      })
   } catch (err) {
      console.error('Something wrong happen')
   }
}

3. 验证生产环境配置

确认生产环境中NEXT_PUBLIC_IP_MQTT环境变量配置正确，服务器能正常访问MQTT服务端口（1883），避免因连接失败导致数据无法更新。

内容的提问来源于stack exchange，提问作者Rizki Ramadhan