如何在使用 NodeJS 和 Express 时创建 MySQL 连接池？

How do I create a MySQL connection pool while working with NodeJS and Express?

提问by Utkarsh Kaushik

I am able to create a MySQL connection like this:

我能够像这样创建一个 MySQL 连接：

var mysql      = require('mysql');
var connection = mysql.createConnection({
    host     : 'localhost',
    user     : 'me',
    password : 'secret',
    database : 'my_db'
});

connection.connect();

But I would rather like to initiate a pool and use it across my project.

但我更愿意启动一个池并在我的项目中使用它。

回答by Utkarsh Kaushik

Just to help some one in future, this worked for me:

只是为了帮助将来的某个人，这对我有用：

I created a mysql connector file containing the pool:

我创建了一个包含池的 mysql 连接器文件：

// Load module
var mysql = require('mysql');
// Initialize pool
var pool      =    mysql.createPool({
    connectionLimit : 10,
    host     : '127.0.0.1',
    user     : 'root',
    password : 'root',
    database : 'db_name',
    debug    :  false
});    
module.exports = pool;

Later you can simply include the connector in another file lets call it manageDB.js:

稍后您可以简单地将连接器包含在另一个文件中，我们称之为 manageDB.js：

var pool = require('./mysqlConnector');

And made a callable method like this:

并制作了一个这样的可调用方法：

exports.executeQuery=function(query,callback){
    pool.getConnection(function(err,connection){
        if (err) {
          connection.release();
          throw err;
        }   
        connection.query(query,function(err,rows){
            connection.release();
            if(!err) {
                callback(null, {rows: rows});
            }           
        });
        connection.on('error', function(err) {      
              throw err;
              return;     
        });
    });
}

回答by Nam Le

There is some bugs in Utkarsh Kaushik solution:

Utkarsh Kaushik 解决方案中存在一些错误：

• if (err), the connection can not be released. connection.release();

• and when it has an err, next statement .queryalways execute although it gets an error and cause the app crashed.

• when the result is null although query success, we need to check if the result is null in this case.

• 如果（错误），则无法释放连接。 connection.release();

• 并且当它有错误时，下一条语句.query总是会执行，尽管它会出错并导致应用程序崩溃。

• 当查询成功但结果为空时，我们需要检查结果是否为空。

This solution worked well in my case:

这个解决方案在我的情况下效果很好：

exports.getPosts=function(callback){
    pool.getConnection(function(err,connection){
        if (err) {
          callback(true);
          return;
        }
        connection.query(query,function(err,results){
            connection.release();
            if(!err) {
                callback(false, {rows: results});
            }
            // check null for results here
        });
        connection.on('error', function(err) {
              callback(true);
              return;
        });
    });
};

回答by sumitjainjr

You can create a connection file, Let's called dbcon.js

您可以创建一个连接文件，我们称之为 dbcon.js

var mysql = require('mysql');

// connect to the db
dbConnectionInfo = {
  host: "localhost",
  port: "3306",
  user: "root",
  password: "root",
  connectionLimit: 5, //mysql connection pool length
  database: "db_name"
};

//For mysql single connection
/* var dbconnection = mysql.createConnection(
        dbConnectionInfo
); 

 dbconnection.connect(function (err) {
    if (!err) {
        console.log("Database is connected ... nn");
    } else {
        console.log("Error connecting database ... nn");
    }
}); 

*/

//create mysql connection pool
var dbconnection = mysql.createPool(
  dbConnectionInfo
);

// Attempt to catch disconnects 
dbconnection.on('connection', function (connection) {
  console.log('DB Connection established');

  connection.on('error', function (err) {
    console.error(new Date(), 'MySQL error', err.code);
  });
  connection.on('close', function (err) {
    console.error(new Date(), 'MySQL close', err);
  });

});


module.exports = dbconnection;

Now include this connection to another file

现在将此连接包含到另一个文件中

var dbconnection = require('../dbcon');
dbconnection.query(query, params, function (error, results, fields) {
    //Do your stuff
});