每次我想使用数据库时，是否都需要打开 MongoDB 连接? [英] Is it necessary to open MongoDB connection every time I want to work with the DB?

问题描述

在我使用的示例中，代码如下:

In the example I am working with is this code:

//lets require/import the mongodb native drivers.
var mongodb = require('mongodb');

//We need to work with "MongoClient" interface in order to connect to a mongodb server.
var MongoClient = mongodb.MongoClient;

// Connection URL. This is where your mongodb server is running.
var url = 'mongodb://localhost:27017/my_database_name';

// Use connect method to connect to the Server
MongoClient.connect(url, function (err, db) {
  if (err) {
    console.log('Unable to connect to the mongoDB server. Error:', err);
  } else {
    //HURRAY!! We are connected. :)
    console.log('Connection established to', url);

    // Get the documents collection
    var collection = db.collection('users');

    //Create some users
    var user1 = {name: 'modulus admin', age: 42, roles: ['admin', 'moderator', 'user']};
    var user2 = {name: 'modulus user', age: 22, roles: ['user']};
    var user3 = {name: 'modulus super admin', age: 92, roles: ['super-admin', 'admin', 'moderator', 'user']};

    // Insert some users
    collection.insert([user1, user2, user3], function (err, result) {
      if (err) {
        console.log(err);
      } else {
        console.log('Inserted %d documents into the "users" collection. The documents inserted with "_id" are:', result.length, result);
      }
      //Close connection
      db.close();
    });
  }
});

如您所见，他正在connect 函数中执行操作.我想保持模块化并将连接与数据库操作分开.

As you may see, he is doing an operation in the connect function. I would like to keep it modular and separate the connection from DB operations.

我的建议是在 db 变量上创建一个单例并重用那个.至少这是我在 Java 中会做的事情，我已经习惯了.

My suggestion would be to make a singleton on db variable and reuse that one. At least that's what I would do in Java to which I am used to.

但是，我不确定，因为在示例中他没有提出类似的建议.

However, I am not sure as in the example he hasn't suggested anything like that.

推荐答案

如果您想要任何类型的可扩展性，我建议不要维护一个连接.

I would recommend against maintaining one connection if you want any kind of scalability.

连接池等有许多选项，但大多数在 Node 和 MongoDB 上花费任何时间的人最终都会在某个时候转向 Mongoose.

There are a number of options for connection pooling, etc, but most folks who spend any time at all with Node and MongoDB end up moving to Mongoose at some point.

除了添加一个不错的schema层之外，它还提供了连接抽象，这样你就可以通过调用mongoose.connect()默认为一个共享连接，或者你可以创建多个连接或参与连接通过调用 mongoose.createConnection() 进行池化.在这两种情况下，您都无需回调即可调用它，并且猫鼬机器会将对该模块的后续调用推迟到建立连接之后，这样您的代码就不必关心了.

In addition to adding a nice schema layer, it offers connection abstraction so that you can default to a shared connection by calling mongoose.connect(), or you can create multiple connections or participate in connection pooling by calling mongoose.createConnection(). In both cases, you call it without a callback, and the mongoose machinery will defer subsequent calls to the module until after the connection is established, so that your code doesn't have to care.

类似于您的用例的内容可能如下所示:

Something like your use case might look like so:

// in your app.js or server.js file
var mongoose = require('mongoose');
mongoose.connect(config.db.url); // assuming you have some module that handles config variables

然后在./models/user.js

Then in ./models/user.js

const mongoose = require('mongoose'),
         Schema   = mongoose.Schema;

   const UserSchema = new Schema({
      name: String,
      age: Number,
      roles: [String]
   });
   mongoose.model('User',UserSchema);

最后，让我们说一个种子函数来创建你的第一批用户:

finally, in lets say a seed function to create your initial batch of users:

const mongoose = require('mongoose'),
      User     = mongoose.model('User');

// create some users
var user1 = new User({name: 'modulus admin', age: 42, roles: ['admin', 'moderator', 'user']});
var user2 = new User({name: 'modulus user', age: 22, roles: ['user']});

user1.save(console.log);
user2.save(console.log);

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