需要我的模塊的多個文件覆蓋它的變量

Question

我想創建一個mongo連接池工廠，檢查是否已經存在一個連接到mongo並返回一個連接。如果它不創建連接池並返回連接。

我希望能夠從多個要查詢mongo的文件中得到這個要求。每個文件應當蒙戈是這樣的：

var fooMongoFactory = require('../../lib/mongoFactory').init(mongodb://localhost:27017/foo); 

，然後你用它在你的文件是這樣的：

fooMongoFactory.getConnection().then(function(db) { 
    // do stuff 
}); 

我遇到的問題是，我希望能夠以指定多個不同mongo實例在一個文件中，但是當這樣做時，我的第二個init覆蓋了第一個。例如：

var fooMongoFactory = require('../../lib/mongoFactory').init(mongodb://localhost:27017/foo); 
var barMongoFactory = require('../../lib/mongoFactory').init(mongodb://localhost:27017/bar); 

fooMongoFactory.getConnection().then(function(db) { 
    // querying in here is actually pointing at the mongo db "bar" 
}); 

我如何調整我的工廠，這樣我可以連接到蒙戈的多個不同的實例，以及使用在多個文件這同一個工廠，而不必每次都實例化了嗎？我想過使用構造函數，但是它會在每個使用mongoFactory的文件中創建一個新的連接池。

/** 
* Creates and manages the Mongo connection pool 
* 
* @type {exports} 
*/ 
var Q = require('q'); 
var MongoClient = require('mongodb').MongoClient; 
var dbPromise = null; 
var db = null; 

module.exports = function() { 

    return { 

    init: function init(connectionString) { 
     db = connectionString; 
     return module.exports; 
    }, 

    /** 
    * Gets a connection to Mongo from the pool. If the pool has not been instantiated it, 
    * instantiates it and returns a connection. Else it just returns a connection from the pool 
    * 
    * @returns {*} - A promise object that will resolve to a mongo db object 
    */ 
    getConnection: function getConnection() { 
     // get a connection to mongo using the db string and return dbPromise 
    } 
    } 
}(); 

Answer 1

我最終創建了模塊，以便您必須傳入要連接到的mongodb的連接字符串。這個模塊最終跟蹤所有與mongo連接的連接，以及是否存在與mongodb連接的當前連接。

/** 
* Creates and manages the Mongo connection pool 
* 
* @type {exports} 
*/ 
var Q = require('q'); 
var MongoClient = require('mongodb').MongoClient; 
var _ = require('underscore'); 

var connections = []; 
var dbPromise = null; 

module.exports = function() { 

    return { 

    /** 
    * Gets a connection to Mongo from the pool. If the pool has not been instantiated it, 
    * instantiates it and returns a connection. Else it just returns a connection from the pool 
    * 
    * @returns {*} - A promise object that will resolve to a mongo db object 
    */ 
    getConnection: function getConnection(connectionString) { 

     var def = Q.defer(); 

      // If connectionString is null or undefined, return an error 
      if(_.isEmpty(connectionString)) { 
       def.reject('getConnection must contain a first parameter'); 
       return dbPromise = def.promise; 
      } 

     // Check if connections contains an object with connectionString equal to the connectionString passed in and set the var to it 
     var pool = _.findWhere(connections, {connectionString: connectionString}); 

     // If no conneciton pool has been instantiated, instantiate it, else return a connection from the pool 
     if(_.isUndefined(pool)) { 

     // Initialize connection once 
     MongoClient.connect(connectionString, function(err, database) { 
      if (err) { 
      def.reject(err); 
      } 

      // Add the connection to the array 
      connections.push({connectionString: connectionString, db: database}); 

      def.resolve(database); 
     }); 

     } else { // Else we have not instantiated the pool yet and we need to 
     def.resolve(pool.db); 
     } 

     return dbPromise = def.promise; 
    } 
    }; 
}(); 

https://github.com/toymachiner62/mongo-factory

Answer 2

的mongodb節點模塊已經有了，當你調用connect()時自動使用built-in connection pooling功能。 default max connection pool size is 5，但是您可以在連接URL中更改此值（例如'mongodb://localhost:27017/foo?maxPoolSize=15'）。

您還需要更改通過在server config options中將poolSize設置爲小於或等於maxPoolSize的某個值創建的實際連接數。您可能還想將auto_reconnect設置爲true。

現在你可以做的是保持一個對象在主機上：包含該服務器的數據庫對象的端口。如果有人傳入包含主機端口的連接字符串，則返回該池。否則，創建，緩存並返回新的數據庫對象。