使用异步/等待的node.js mysql池连接 [英] node.js mysql pool connection with async/ await

问题描述

是否可以使用以async/ await语法从mysqljs/mysql库获取的pool.getConnection()?

Is there a way to use pool.getConnection() taken from the mysqljs/mysql lib with the async/ await syntax?

这个想法是要有一种方法，该方法可以返回一个连接，该连接可以在具有各种外键约束(顺序查询)的写查询之间传递，然后再释放该连接，同时有可能从池中获得进一步的连接，以实现以下目的:各种读取查询(并行).

The idea is to have a method which returns one connection which can be passed around amongst write queries with various foreign key constraints (sequential queries) before releasing it and at the same time potentially get further connections from the pool for the purpose of various read queries (parallel).

推荐答案

分享我的工作示例:

我使用此用于Node.js的承诺的MySQL中间件

阅读本文这是我的database.js

here is my database.js

var mysql = require('mysql'); 

// node -v must > 8.x 
var util = require('util');


//  !!!!! for node version < 8.x only  !!!!!
// npm install util.promisify
//require('util.promisify').shim();
// -v < 8.x  has problem with async await so upgrade -v to v9.6.1 for this to work. 



// connection pool https://github.com/mysqljs/mysql   [1]
var pool = mysql.createPool({
  connectionLimit : process.env.mysql_connection_pool_Limit, // default:10
  host     : process.env.mysql_host,
  user     : process.env.mysql_user,
  password : process.env.mysql_password,
  database : process.env.mysql_database
})


// Ping database to check for common exception errors.
pool.getConnection((err, connection) => {
if (err) {
    if (err.code === 'PROTOCOL_CONNECTION_LOST') {
        console.error('Database connection was closed.')
    }
    if (err.code === 'ER_CON_COUNT_ERROR') {
        console.error('Database has too many connections.')
    }
    if (err.code === 'ECONNREFUSED') {
        console.error('Database connection was refused.')
    }
}

if (connection) connection.release()

 return
 })

// Promisify for Node.js async/await.
 pool.query = util.promisify(pool.query)



 module.exports = pool

您必须升级节点-v> 8.x

You must upgrade node -v > 8.x

必须使用异步功能才能使用等待状态.

you must use async function to be able to use await.

示例:

   var pool = require('./database')

  // node -v must > 8.x, --> async / await  
  router.get('/:template', async function(req, res, next) 
  {
      ...
    try {
         var _sql_rest_url = 'SELECT * FROM arcgis_viewer.rest_url WHERE id='+ _url_id;
         var rows = await pool.query(_sql_rest_url)

         _url  = rows[0].rest_url // first record, property name is 'rest_url'
         if (_center_lat   == null) {_center_lat = rows[0].center_lat  }
         if (_center_long  == null) {_center_long= rows[0].center_long }
         if (_center_zoom  == null) {_center_zoom= rows[0].center_zoom }          
         _place = rows[0].place


       } catch(err) {
                        throw new Error(err)
       }

这篇关于使用异步/等待的node.js mysql池连接的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！