Socket.IO服务器的奇怪行为

Question

My Socket.IO client starts making endless requests to server after few hours of working...

So. There is the server that counts peoples online:

const http = require('http');
const io = require('socket.io');

const app = http.createServer();
const socket_io = io.listen(app);

app.listen(2053); 

let clients = [];
    socket_io.sockets.on('connection', (socket) => {
      let ip = socket.handshake.headers['x-real-ip'];
      if (ip && !clients.hasOwnProperty(ip)) {
        clients[ip] = 1;
      }

      socket.on('disconnect', () => {
        if (ip && clients.hasOwnProperty(ip)) {
          delete clients[ip];
        }
      });
    });

    let tick = () => {
      let _online = Object.keys(clients).length;
      socket_io.sockets.emit('changeOnlineEvent', { 'online': _online });
      setTimeout(tick, 2000);
    };
    setTimeout(tick, 2000);

and emits statistic to clients every 2 seconds. Looks easy.

This is the client:

let socket = io.connect('http://domain:port',
{
  'reconnection': true,
  'reconnectionAttempts': 2
});
socket.on('changeOnlineEvent', (object) => {
 console.log(object.online);
});

But after few hours (6-12 hrs) of working every client starts making endless requests to the io.server: As you can see every response is 200 OK and have right response body.

At this time I begin to see a terrible image in zabbix:

Reload the page in browser does not help. And there is no one error in server's console while running io server app. Everything is ok.

The only thing that helps in this situation - restarting nodejs app :-(

I have no idea whats wrong and how to debug this. Need help. Thx.

Answer 1

1. You can try to use only websocket transport. See https://socket.io/docs/client-api/#With-websocket-transport-only (the endless requests, because in polling mode client asking server for updates at certain regular intervals)
2. You can get more logs from the server if you run the server as follows: DEBUG=engine:socket node index.js (socket.io uses debug package https://www.npmjs.com/package/debug )