在MongoDB和Node.js中使用连接

Question

我有连接到mongoDB并获取集合中文档数量的node.js文件，然后它在for循环中运行，并使用从外部服务器获取的值更新每个文档，事实是我一次有很多连接打开，程序崩溃了，我的问题是我如何一次使用1个连接 ，而多个连接是我的代码：

var request = require('request');
var cheerio = require ('cheerio');
var fs = require('fs');
var MongoClient = require('mongodb').MongoClient;



//var config = JSON.parse(fs.readFileSync("config.json"));
//var host =  config.host;
//var port = config.port;



    // Variable Deceleration 

    //var dbName = "ystocks";
    var port = "27017";
    var host = "localhost";
    var collection = "stocks"
    var dbName = "yahooStocks";


    function updateStock(){

        // getting the number of docs in the collection
        getNumOfDocs("stocks", host, port, dbName, function(err, count) {
           if (err) {
               return console.log(err.message);
           }
           console.log('number of documents', count);

        for(i = 0 ; i <= 20; i++)
        {
            // Finding each document by _id with a callbak
            GetDocumentByID("stocks", host, port, dbName, i, function(err, findOne) {
               if (err) {
                   return console.log(err.message);
               }
               console.log('Here is the doc that was found', findOne.ticker);


                var stockName = findOne.ticker;

                console.log("\n* stock name : " +stockName + "\n");
                var yUrl    = "http://finance.yahoo.com/q/ks?s=" + stockName;


                getStockValue(stockName, yUrl); 
            }); // end of GetDocumentByID
        }//end of for loop

    }); // end of getNumOfDocs call
    }// end of update function

    ////passed arguments 
    //stockName = for printing stock name to console
    //yUrl = the specific url for the current stock ticker
    function getStockValue(stockName, yUrl){
        request(yUrl, stockName,  function (error, response, body) {



        var date  = setTimeToLocal(new Date(), 3);


            if (!error && response.statusCode == 200) {         
                var $ =  cheerio.load(body);                    

                // the keys - We get them from a certain class attribute
                var span =  $('.time_rtq_ticker>span');
                var stockValue = $(span).text();
                console.log("checking the type of the stockValue " +  typeof(stockValue));

                //*************************************
                // parsing the value to int in case it was a String

                var parsedValue = parseFloat(stockValue);
                console.log("checking the type of the stockValue " +  typeof(parsedValue) + " " + parsedValue);

                // Calling the setStockValue function which will update the stock value
                setStockValue(stockName, parsedValue);
                //writehead ???
                //response.writeHead(200, {'Content-Type':'text/plain'});

                console.log("Response received from -> " + yUrl);
                console.log(date);
                console.log("Stock  - " + stockName + " --> " + stockValue ); 

                //response.write is for printing in browser when we have a server running      
                //response.write("Welcome to stockwatch\n");
                //response.write("Stock  - " + ticker + " current value--> " + stockValue + "\n" );

                //TODO #1
                //ALEX : lines 61-72 -> should be replaced with a function call that 
                // connects to the DB and updates the specified stock
                //i think it sould look like this : funcName( tickerName , currenValue ){...}
                var json = {stockName : "", price : "", date : ""}; 
                json.price = stockValue;
                json.stockName = stockName;
                json.date = date;

                var tempName = json.stockName +'.json';

                fs.writeFile( tempName ,JSON.stringify(json, null, 4) , function(err) {         
                    if(!err) {
                        console.log("File successfully written");
                    }           
                });//end of filewrite
                //end of TODO #1

                //response.end("res end");

            }//end of !error && response.statusCode == 200

            else if (response.statusCode == 404){
                    console.log("Response failed from " + yUrl + " --> error code:  " +  response.statusCode);
                }//end of statusCode == 400
        });// end of request
    }//end of getStockValue

    // updating a stock with a provided ticker and value and the MongoClient
    // edited by Alex Brodov on : AUG 21 2014

    function setStockValue(ticker, value) {
        // open the connection the DB server

        MongoClient.connect("mongodb://localhost:27017/yahooStocks", function (error, db){

            if(error) throw error;

            var query = {'ticker' : ticker};
            operator ={'$set' : {'value' : value}};
            // find one document in our collection
            db.collection('stocks').update(query, operator, function(error, updated){
                if (error) throw error;

                //print the result
                console.dir("Successfully updated " + updated + " document");

                // close the DB
                db.close();

            });// end of update



        }); // Connection to the DB

    } //  end of setStockValue


    // Gets the local date and the desired offset time
    // set 
    function setTimeToLocal(date, offset ) {
        // getting the local tome in millseconds 
            var localtime = date.getTime();

            // getting the local offset in millseconds
            var localOffset = date.getTimezoneOffset()*60000;

            var utc = localOffset + localtime;

            // Jerusalem offset
            //  var offset = 3;

            // Jerusalem time in millseconds
            var jerusalem =  utc + (offset*3600000);
            var d = new Date(jerusalem);
            console.log("Jerusalem Local Time: " + d.toLocaleString());
            return d;
    } // end of SetTimeToLocal

    /** 
    * Gets the number of documents from a collection 
    * With a provided collection name, DB host, DB port, DB name and a callback function
    * Edited by Alex
    */

    function getNumOfDocs (collectionName, host, port, dbName, callback) {
     var mongoConnection =    MongoClient.connect("mongodb://" + host + ":" + port + "/" + dbName, function (error, db){
            if(error) return callback(err);

            db.collection(collectionName).count({}, function(error, numOfDocs){
                if(error) return callback(err);

                db.close();
                callback(null, numOfDocs);
            }); // end of count 
        }); // end of connection to DB
   } // end of getNumOfDocs

/**
* Gets a document 
* With a provided collection name, DB host, DB port, DB name, the document ID and a callback
* Edited by Alex Brodov on Aug 24th 2014
*/

function GetDocumentByID (collectionName, host, port, dbName, docID, callback) {

    // open the connection to DB server
    MongoClient.connect("mongodb://" + host + ":" + port + "/" + dbName, function (error, db){

        if(error) return callback(error);

        var query = {'_id' : docID};
        // find one document in our collection
        db.collection(collectionName).findOne(query, function(error, doc) {
            if (error) return callback(error);
            console.log(doc);
           // close the DB
            db.close();
            callback(null, doc);

        });// end of findOne
    }); // Connection to the DB
}
var refreshInterval = setInterval(updateStock, 30000);

Answer 1

在MongoDB / Node应用程序中，应该在启动时执行一次MongoClient.connect（），然后根据需要直接重复使用db对象。 实际上，MongoClient是一个连接池，效率很高。

因此，您应该检查代码，仅连接一次，这样就可以解决问题（更快的程序和更少的连接）

1. 从程序中删除所有mongoclientconnect，回调和db.close

2. 他们添加以下“围绕您的代码”

 MongoClient.connect("mongodb://localhost:27017/yahooStocks", function (error, db){ if(error) throw error; // all your methods here // ... // .. var refreshInterval = setInterval(updateStock, 3000); });