Question

我想知道如何使用MEAN堆栈应用程序中的数据库连接。特别是，何时应该创建与数据库的连接，何时应该销毁与数据库的连接。我应该在每个新的HTTP请求上创建和销毁连接，还是应该存储一次创建的连接，并尽可能长时间地将其用于任何后续请求。我使用Mongoose作为建模工具。

这是一个例子。这是我的routes.js文件，其中包含路由/index。对此路由的请求应从MongoDb数据库中获取一些日期。现在我困扰我如何连接和断开数据库。是的，我完全按照Mongoose docs中的说法连接和断开数据库，但它是在严肃的生产环境中进行的正确方法吗？

var express = require('express');
var router = express.Router();

var config = require('./db-config');

// I create a Mongoose instance as a module object,
// as opposite to create it in every request handler function below.
var mongoose = require('mongoose');

var productSchema = require('../db/productSchema'); // model schema is also a module-wide object

// And here is a request handler function.
// It is called on every request as a brand new.
// I create and destroy a database connection inside this request handler
router.get('/index', function(req, res, next) {

    // I connect to a database on every request.
    // Do I need to do it here in a request handler?
    // May I do it outside of this request handler on a module-wide level?
    mongoose.connect('mongodb://my_database');

    // I create a new connection here in a request handler.
    // So it lives only during this request handler run.
    // Is this the right way? May I do it outside of this request handler 
    // on a module-wide level and somehow keep this connection and use it 
    // in every subsequent requests to this or any other route in the app?
    var db = mongoose.connection;

    db.on('connecting', function() {
        console.log('connecting');
    });

    db.on('connected', function() {
        console.log('connected');
    });

    db.on('open', function() {
        console.log('open');
    });

    db.on('error', console.error.bind(console, 'connection error'));

    db.once('open', function(cb) {
        var Product = mongoose.model('Product', productSchema);
        Product.find({category: "books"}, function(err, prods) {
            if (err) return console.error(err);

            // I close a connection here in a callback. 
            // As soon as successfully fetched the data. 
            // Do I need to close it after every request? 
            // What is the right place and time to do it? 
            db.close(disconnect);
            res.json(prods);
        });
    });
})

找到了一些好的答案：

https://softwareengineering.stackexchange.com/questions/142065/creating-database-connections-do-it-once-or-for-each-query

What are best practices on managing database connections in .NET?

Answer 1

将数据库连接放在单独的模块（db.js）

中的最佳做法

var mongoose = require('mongoose')

mongoose.connect('mongodb://localhost/dbname', function(){
    console.log('mongodb connected')
})
module.exports = mongoose

每个模型都应该有一个单独的模块，它接受数据库连接（post.js）

var db = require('../db.js')
var Post = db.model('Post', {
    username: {type: String, required: true},
    body: {type: String, required: true},
    date: { type: Date, required: true, default: Date.now }  
})

module.exports = Post

然后，只要您需要使用该数据集，只需要它并进行调用

var Post = require('/models/post')
Post.save()
Post.find()

Answer 2

这是一个基于意见的问题我会说。我用于我的应用程序的是

app.get('/', function (req, res) {
res.sendfile('index.html');
});
mongoose.connect('mongodb://localhost:27017/my_db');

这样我创建一次连接而不是每个HTTP请求。你的方式应该可以正常工作但似乎你必须连接并断开数据库与应用程序的连接太多次特别是在应用程序处于开发阶段时。

Answer 3

你希望你的连接像一个单身人士一样行动，正如上面的答案所提到的那样，在你的路线之外做这件事是有意义的，并且最好在你的路线之前做到：

var compression = require('compression');
var express  = require('express');
var app      = express();
var port     = process.env.PORT || 8080;
var cookieParser = require('cookie-parser');
var bodyParser   = require('body-parser');
var session      = require('express-session');
...

app.use(compression());
// db
var mongoose = require('mongoose');
var configDB = require('./config/database.js');
mongoose.connect(configDB.url); // connect to our database

配置/ database.js：

module.exports = {
'url' : '@localhost:27017/dbname'
};

Answer 4

这是我的解决方案：

import express from 'express';
import mongoose from 'mongoose';
import { name } from '../package.json';
import * as localconfig from './local-config';
import debug from 'debug';
debug(name);
const app = express();

const port = process.env.PORT || 3000;
const mongoUrl = localconfig.credentials.MONGO_URL;

import usersRoutes from './routes/users/user-routes';

app.use('/v1/users', usersRoutes);

mongoose.connect(mongoUrl)
    .then(() => {
        debug('DB connection successful');
        app.listen(port, '0.0.0.0', () => {
            debug(`Running on port ${port}`);
        });
    })
    .catch((err) => {
        debug(err);
    });

您应该首先检查天气连接是否成功，然后再侦听某个端口。这是我的app.js文件，所有路由均已加载，因此您不必在所有文件中都调用db连接。您只有一个配置文件，所有配置都已完成。您的路由器文件user-routes.js看起来类似于：

import express from 'express';

import User from '../models/user'
const router = express.Router();

router.get('/', (req, res, next) => {
    User.find()
        .then((response) => res.json(response))
        .catch((err) => next(err));
});

module.exports = router;

连接/断开连接到数据库的最佳做法是什么？

4 个答案: