Simple server on node js

Question

Hello all :) My problem is that is not working response.vrite () Why ? And another question. Will be called db.open each boot / upgrade page?

var http = require("http");
var Db = require ("mongodb").Db;
var Server = require("mongodb").Server;
function start () {
'use strict';
function onRequest (request, response) {
    'use strict';
    var db = new Db ("TestApp", new Server ("127.0.0.1", 27017, {}));
    response.writeHead(200, {"Content-Type": "application/json", "Access-Control-Allow-Origin": "*"});
    db.open (function (err, db, response) {
        db.collection ('ObjectCollection', function (err, collection) {
            collection.find().toArray (function (err, docs) {
                console.log (docs);
                response.write(JSON.stringify(docs));
            });
        });
    });
    response.end();
}

http.createServer(onRequest).listen(8080);
console.log ('Server has started...')
}exports.start = start;

Did you check what the console is printing out?

Joseph
– Joseph

2012-12-02 05:25:52 +00:00
Commented Dec 2, 2012 at 5:25 — Joseph
– Joseph, Commented Dec 2, 2012 at 5:25

JohnnyHK · Accepted Answer · 2012-12-02 05:31:49Z

2

You're calling response.end before your response.write. Move the response.end call inside the callbacks like this:

var http = require("http");
var Db = require ("mongodb").Db;
var Server = require("mongodb").Server;
function start () {
'use strict';
function onRequest (request, response) {
    'use strict';
    var db = new Db ("TestApp", new Server ("127.0.0.1", 27017, {}));
    response.writeHead(200, {"Content-Type": "application/json", "Access-Control-Allow-Origin": "*"});
    db.open (function (err, db, response) {
        db.collection ('ObjectCollection', function (err, collection) {
            collection.find().toArray (function (err, docs) {
                console.log (docs);
                response.write(JSON.stringify(docs));
                response.end();
            });
        });
    });
}

http.createServer(onRequest).listen(8080);
console.log ('Server has started...')
}
exports.start = start;

And yes, a new Db object will be opened on each request so it would be better to open that once during startup.

answered Dec 2, 2012 at 5:31

JohnnyHK

313k70 gold badges632 silver badges479 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

JohnnyHK Over a year ago

@user1852858 My pleasure, and welcome to SO. If this answered your question click the check mark to the left of the answer to confirm it.

Andrew Rhyne · Accepted Answer · 2012-12-02 05:46:21Z

1

Like Johnny said, your calling response.end() outside of your asynchronous functionality. As a rule, you should never count on callbacks actually executing in a blocking manner unless you KNOW how their parent function works under the hood. DB.open likely runs that callback upon connection completion, and we don't know how long that will take. Since DB.Open is non-blocking, node then executes the response.end before DB.open's asynchronous call to the database likely even completes. You may want to read up a bit on asynchronous javascript

answered Dec 2, 2012 at 5:46

Andrew Rhyne

5,0705 gold badges31 silver badges42 bronze badges

Collectives™ on Stack Overflow

Simple server on node js

2 Answers 2

1 Comment

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Related