我收到無法讀取的不確定

Question

財產「查詢」我已經鑄成socket.io聊天室，我使用一些數據庫查詢，插入和選擇數據但不幸的是我得到的查詢

的代碼的一些錯誤上我得到錯誤的文件是遵循

var rooms = []; 
module.exports.getUserFeeds = function (chatpage, socket, io, pool,async) 
{ 
    socket.on('senddata', function (data) 
    { 
     socket.user_id = data.user_id; 
     socket.room_id=data.room_id; 
     socket.room = 'room' + data.room_id; 
     rooms['room' + data.room_id] = 'room' + data.room_id; 
     socket.join('room' + data.room_id); 
     pool.getConnection(function (err, connection) 
     { 
      async.parallel([ 
       function(callback) 
       { 
        connection.query('SELECT user_id,username FROM chat_users where user_id=' + data.user_id + '', function (error1, userdata) 
        { 
         if (error1) return callback(error1); 
         callback(null, userdata); 
        }); 
       }, 
       function (callback) 
       { 
        if(data.user_id) 
        connection.query('SELECT user_id,username FROM chat_users', function (error3, memdata) 
        { 
         if (error3) return callback(error3); 
         callback(null, memdata); 
        }); 
        else 
         callback(null,null); 
       }, 
       function(callback) 
       { 
        if(data.user_id) 
        connection.query('SELECT comment_id,comment,chat_users.user_id,username,comments.added FROM comments INNER JOIN chat_users ON comments.user_id=chat_users.user_id',function(error4,converdata){ 
         if (error4) return callback(error4); 
         callback(null, converdata); 
        }); 
        else 
         callback(null,null); 
       } 
      ], function (err, results) 
       { 
        if(err) throw err; 
        socket.emit('chatdata', 
        { 
         memdata:results[1], 
         converdata:results[2], 
        }); 
        socket.broadcast.to('room'+ data.room_id +'').emit('newuser', {userdata:results[0]}); 
        connection.release(); 
       }); 
     }); 
    }); 

    socket.on('sendcomment', function (data) 
    { 
     pool.getConnection(function (err, connection) 
     { 
      connection.query('INSERT INTO comments (user_id,comment,added) VALUES (' + data.user_id + ',"' + data.msg + '","' + data.datetime + '")', function (err, result) 
      { 
       if (err) throw err; 
       async.parallel([ 
        function (callback) 
        { 
         connection.query('SELECT comments.*,username,comments.added from comments JOIN chat_users ON comments.user_id=chat_users.user_id WHERE comments.comment_id=' + result.insertId + '', function (err2, comments) 
         { 
          if (err2) return callback(err2); 
          callback(null, comments); 
         }); 
        }, 
        function (callback) 
        { 
         connection.query('SELECT count(comment_id) as tot_comment from comments', function (err3, comment_count) 
         { 
          if (err3) return callback(err3); 
          callback(null, comment_count); 
         }); 
        }, 
        ], function (err, results) 
        { 
         if (err) throw err; 
         if (results[0]) 
         { 
          chatpage. in('room'+ data.room_id +'').emit('showcomment', 
          { 
           room_comment: results[0], 
           comment_count: results[1] 
          }); 
         } 
         connection.release(); 
        }); 
      }); 
     }); 
    }); 
    socket.on('disconnect', function() 
    { 
     console.log("user disconnected"); 
     pool.getConnection(function (err, connection) 
     { 
      connection.query('DELETE from chat_users where user_id='+socket.user_id+'', function (err, removeuser) 
      { 
       if (err) throw err; 
      }); 
      connection.query('DELETE from comments where user_id='+socket.user_id+'', function (err, removecomments) 
      { 
       if (err) throw err; 
      }); 
      connection.release(); 
     }); 
     socket.broadcast.to('room'+ socket.room_id +'').emit('removeuser', {user_id:socket.user_id}); 
     socket.leave(socket.room); 
    }); 

}; 

和我是因爲這個代碼得到的錯誤是

The image of the error i am getting

請誰能幫助我在這個問題

非常感謝 問候

Answer 1

似乎有在你的mysql connection.try做出正確連接第一

第1步錯誤：創建池（只這樣做一次）

var mysql = require('mysql'); 
var pool = mysql.createPool({ 
    host   : 'hostname', 
    user   : 'username', 
    password  : 'password', 
    database  : 'db_name', 
    connectionLimit : 10,    // this is the max number of connections before your pool starts waiting for a release 
    multipleStatements : true   // I like this because it helps prevent nested sql statements, it can be buggy though, so be careful 
}); 

第2步：獲取連接

pool.getConnection(function (err, conn) { 
    if (err) 
     return res.send(400); 

    // if you got a connection... 
    conn.query('SELECT * FROM table WHERE id=? AND name=?', [id, name], function(err, rows) { 
     if(err) { 
      conn.release(); 
      return res.send(400, 'Couldnt get a connection'); 
     } 

     // for simplicity, just send the rows 
     res.send(rows); 

     // CLOSE THE CONNECTION 
     conn.release(); 
    } 
}); 

檢查本作更詳細https://youtu.be/2CeAnrCsBQo

http://fearby.com/article/how-to-setup-pooled-mysql-connections-in-node-js-that-dont-disconnect/

Answer 2

你需要處理錯誤，否則你可能會遇到這樣的問題。具體來說，在這種情況下，您不會檢查是否設置在您的pool.getConnection()回調中。這是最有可能的設置，並且是爲什麼你沒有一個有效的connection對象。