mysql - 管道 `request` 响应 MySQL 回调中的服务器响应未按预期工作？ Node

Question

我在尝试理解为什么我在下面提供的代码没有按预期工作时遇到了令人沮丧的事情。基本概念是:

浏览器 -> Nodejs 服务器 -> MySQL 回调 -> 请求 -> 服务器响应。

有人能解释一下为什么下面的代码能按预期工作吗。

// Load modules
var http        = require('http');
var https       = require('https');
var httpProxy   = require('http-proxy'); 
var url         = require('url');
var qstr        = require('querystring');
var path        = require('path');
var requester   = require('request');

var server = httpProxy.createServer(function(request, response) { 

    proxy = requester({
      url: 'http://www.srcnix.com',
      method: 'GET'
    });      

    request.pipe(proxy);
    proxy.pipe(response);

});

server.listen(8080);

但是，当我将请求和管道放在回调中时，无论是在 MySQL 查询回调(如下所示)还是在另一个请求回调中，它都无法将响应通过管道传递给服务器。

// Load modules
var http        = require('http');
var https       = require('https');
var httpProxy   = require('http-proxy'); 
var url         = require('url');
var qstr        = require('querystring');
var path        = require('path');
var requester   = require('request');

var globalConf  = require('./config/global.js');

var mysql       = require('mysql');
var connection  = mysql.createConnection({
  host:     globalConf.db.portal.host,
  user:     globalConf.db.portal.username,
  password: globalConf.db.portal.password,
  database: globalConf.db.portal.database
});

var server = httpProxy.createServer(function(request, response) { 
  connection.query('SELECT 1', function(err, rows) {        
    if(rows.length) 
    {
      proxy = requester({
        url: 'http://www.srcnix.com',
        method: 'GET'
      });      

      // PIPE FAILS TO WORK!                
      request.pipe(proxy);
      proxy.pipe(response);
    }
  });      
});

server.listen(8080);

非常欢迎您的想法和知识，并在此先感谢您。

Answer 1

因为对 mysql 的查询是异步的，当时间结束时，请求已完成发出所有数据。您需要暂停请求，直到回调完成。

var server = httpProxy.createServer(function(request, response) {
  request.pause();
  connection.query('SELECT 1', function(err, rows) {        
    if(rows.length) 
    {
      request.resume();
      proxy = requester({
        url: 'http://www.srcnix.com',
        method: 'GET'
      });      

      // PIPE FAILS TO WORK!                
      request.pipe(proxy);
      proxy.pipe(response);
    }
  });      
});

Have a look here, this is where i got the response from and worked for me!