javascript - MaxListenersExceededWarning：检测到可能的 EventEmitter 内存泄漏。添加了 11 个消息列表。使用emitter.setMaxListeners() 增加限制

Question

我知道这可能会标记为重复的解决方案，但堆栈溢出的解决方案对我不起作用。

问题

(node:5716) MaxListenersExceededWarning: Possible EventEmitter memory leak detected. 11 message lis
teners added. Use emitter.setMaxListeners() to increase limit.

我的代码库很大，有时我会遇到这个错误，我不知道为什么会这样。我试图增加听众限制，但不幸的是，它不起作用。

const EventEmitter = require('events');
const emitter = new EventEmitter()
emitter.setMaxListeners(50)

更新

浏览一番后，我运行此命令来跟踪警告

node --trace-warnings index.babel.js

原来是我的 socket.io 代码是我将 socket.io 与 Redis 一起使用的问题。这是错误

node:14212) MaxListenersExceededWarning: Possible EventEmitter memory leak detected. 11 message li
steners added. Use emitter.setMaxListeners() to increase limit
    at _addListener (events.js:281:19)
    at RedisClient.addListener (events.js:298:10)
    at Namespace.<anonymous> (D:/newProject/services/socket.js:21:17)
    at emitOne (events.js:115:13)
    at Namespace.emit (events.js:210:7)
    at Namespace.emit (D:\newProject\node_modules\socket.io\lib\namespace.js:213:10)
    at D:\newProject\node_modules\socket.io\lib\namespace.js:181:14
    at _combinedTickCallback (internal/process/next_tick.js:131:7)
    at process._tickCallback (internal/process/next_tick.js:180:9)

这是代码（但此代码用于更具体的任务，它不会一直执行）。

const redis = require('redis');
const config = require('../config');
const sub = redis.createClient(config.REDIS.port, config.REDIS.host);
const pub = redis.createClient(config.REDIS.port, config.REDIS.host);

sub.subscribe('spread');

module.exports = io => {
  io.on('connection', socket => {
    /* To find the User Login  */
    let passport = socket.handshake.session.passport; 

    if (typeof passport !== 'undefined') {
      socket.on('typing:send', data => {
        pub.publish('spread', JSON.stringify(data));
      });

      sub.on('message', (ch, msg) => {
        // This is the Exact line where I am getting this error
        io.emit(`${JSON.parse(msg).commonID}:receive`, { ...JSON.parse(msg) });
      });
    }
  });
};

标签： javascriptmysqlnode.jsreactjs

Answer 1

Event Emitter的默认限制是 10。您可以使用emitter.setMaxListeners 增加它。我的建议是除非明确要求，否则不要更改它，因为您没有取消订阅，所以听众增加了。现在到你的代码。

const redis = require('redis');
const config = require('../config');
const sub = redis.createClient(config.REDIS.port, config.REDIS.host);
const pub = redis.createClient(config.REDIS.port, config.REDIS.host);

sub.subscribe('spread');

module.exports = (io) => {
  io.on('connection', (socket) => {
    // this callback will be executed for all the socket connections.
    let passport =
      socket.handshake.session.passport; /* To find the User Login  */

    if (typeof passport !== 'undefined') {
      socket.on('typing:send', (data) => {
        pub.publish('spread', JSON.stringify(data));
      });

      // this is where you are subscribing for each and every socket connected to your server
      sub.on('message', (ch, msg) => {
        // this is the Exact line where I am getting this error

        // whereas you are emitting messages on socket manager, not on the socket.
        io.emit(`${JSON.parse(msg).commonID}:receive`, { ...JSON.parse(msg) });
      });
    }
  });
};

现在，如果我们分析上面的代码，那么如果你打开 20 个到服务器的套接字连接，它将订阅 20 次，这里出错了。现在，如果您的要求是在服务器级别侦听 Redis 上发布的消息，然后在 io 上发出它，那么您的代码应该如下所示

const redis = require('redis');
const config = require('../config');
const sub = redis.createClient(config.REDIS.port, config.REDIS.host);
const pub = redis.createClient(config.REDIS.port, config.REDIS.host);

sub.subscribe('spread');

module.exports = (io) => {
  sub.on('message', (ch, msg) => {
    // this is the Exact line where I am getting this error
    io.emit(`${JSON.parse(msg).commonID}:receive`, { ...JSON.parse(msg) });
  });

  io.on('connection', (socket) => {
    let passport =
      socket.handshake.session.passport; /* To find the User Login  */

    if (typeof passport !== 'undefined') {
      socket.on('typing:send', (data) => {
        pub.publish('spread', JSON.stringify(data));
      });
    }
  });
};