如何使用节点js和socket.io在mysql数据库中插入新记录时通知和更新客户端。

Question

无法使用mysql节点js和socket.io更新客户端中的记录列表

大家好，我想更新客户端时，新的记录是插入到mysql数据库，即时通讯使用节点js和socket.io。

我能做些什么来解决这个问题呢?我是node和socket的新手，如果我的代码太混乱，请原谅。我找了很久，但什么也没找到。任何建议都会有帮助。这是我的server.js文件：

    var mysql = require('mysql') ;
var io = require('socket.io').listen(3000) ;

var db = mysql.createConnection({
    host:'localhost',
    user:'root',
    database:'mygame'
});

db.connect(function(err){
    if(err) console.log(err);
    console.log("Connected Successfully To The Database");
});

// Here We Need List Of Competitions To Emit To All Clients 

var Competitions = [] ;
var isInitCompetitions = false ;
var socketCount = 0 ;

//
io.sockets.on('connection',function(socket){
    Competitions = [];
    db.query("SELECT * FROM comps WHERE compstatus='1'").on(
        'result',function(data) {

            Competitions.push(data) ;
        }
    ).on(
        'end',function(){
            socket.emit('all competitions',Competitions);
        }
    ) ;
    socketCount++ ;
    io.sockets.emit('Another User Is Connected : ' ,socketCount);
    console.log('One User Is Connected');
    socket.on('disconnect',function() {
        io.sockets.emit('One User Left : ' ,socketCount);
    });

    function checkNewCompetitions() {
        socket.on('newcomp',function(){
            db.query("SELECT * FROM comps WHERE compstatus='1'").on(
                'result',function(data) {
                    Competitions = [];
                    Competitions.push(data) ; 
                }
            ).on(
                'end',function(){
                    socket.emit('all competitions',Competitions);
                    console.log('Number Of Competitions in Flow : ' , Competitions.length) ;
                }
            ) ;
        });
    }
    setInterval(checkNewCompetitions,3000);



});

下面是我的index.html文件：

<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js"></script>
<script src="http://localhost:3000/socket.io/socket.io.js"></script>
<script>
    $(document).ready(function() {
        var socket = io.connect('http://localhost:3000');
        socket.on('all competitions',function(data) {
           var html = ''  ;
           for(var i = 0 ;i < data.length; i++){
               html += '<li>'+data[i].id + '</li>';
           }
           $('#competitions').html(html);
        });
        socket.on('newcomp',function(data) {
           var html = ''  ;
           for (let index = 0; index < data.length; index++) {
               const element = data[index];
               html += '<li>' + data[index].id + '</li>';
           }
           $('#competitions').html(html);
        });
    });
</script>
<p>This is List Of Competitions</p>
<ul id="competitions"></ul>

我运行了这段代码，但是我得到了这个错误：

(node:8628) MaxListenersExceededWarning: Possible EventEmitter memory leak detected. 11 newcomp listeners added. Use emitter.setMaxListeners() to increase limit

感谢这个伟大的社区，我能为这个问题做些什么呢？

Answer 1

每隔3秒添加一个新的事件侦听器，这样就会发生MaxListenersExceededWarning。每隔3秒调用一次checkNewCompitions就可以了。如果有一个新的comp，你必须用socket.emit(' newComp ')发出一个newcomp事件

    socketCount++ ;
    io.sockets.emit('Another User Is Connected : ' ,socketCount);
    console.log('One User Is Connected');
    socket.on('disconnect',function() {
        io.sockets.emit('One User Left : ' ,socketCount);
    });

    function checkNewCompetitions() {
/// Every 3 seconds you check the database for new comps
            db.query("SELECT * FROM comps WHERE compstatus='1'").on(
                'result',function(data) {
                    Competitions = [];
                    Competitions.push(data) ; 
                }
            ).on(
                'end',function(){

// here you have to call socket.emit('newComp') 
// so the client gets the event a new comp is inserted in database. 

                    socket.emit('all competitions',Competitions);
                    console.log('Number Of Competitions in Flow : ' , Competitions.length) ;
                }
            ) ;

    }
    setInterval(checkNewCompetitions,3000);

});

我找不到你在哪里发出了'newcomp‘事件。所以socket.on('newcomp'..)永远不会被呼叫