nodejs - why does my async function run twice?

Question

I am new to node.js and learning from tutorials online. I was trying out the following piece of code :

var http = require("http");

// create a server
http.createServer(function(req, res) {
    console.log("Received Request");
    res.writeHead(200, {'Content-Type':'application/json'});
    res.end("{'status':'200', 'message':'Hello World'}");
    console.log("Response Sent");
}).listen(process.env.PORT, process.env.IP);

I did receive the correct response but in console the output was :

Received Request
Response Sent
Received Request
Response Sent

I wanted to know why was my code running twice ?? Am I making some mistake ? Please help !!

This is almost certainly due to a browser making a second request for the favicon resource. Try `console.log("Received Request", req.url);` — apsillers, Mar 21 '16 at 17:23
Can you give an example how you send the request to the server? browser/curl/other — little, Mar 21 '16 at 17:25
I think apsillers is correct, I dint think of that. @micmic I am using c9 for development, I wrote the code shown above, pressed the RUN button which deployed this code and then hit the url by copying it to the clipboard and pasting in browser address bar and then hitting enter, thats it. — sensitive_piece_of_horseflesh, Mar 21 '16 at 17:28

score 3 · Answer 1 · answered Mar 21 '16 at 17:27

the best way to debug is to check the url

var http = require("http");

// create a server
http.createServer(function(req, res) {
    console.log(req.url);//add this line, I hope it will help
    console.log("Received Request");
    res.writeHead(200, {'Content-Type':'application/json'});
    res.end("{'status':'200', 'message':'Hello World'}");
    console.log("Response Sent");
}).listen(process.env.PORT, process.env.IP);

Also as Bassam Rubaye pointed out it might most likely due to favicon in your case

+ for answers that teach you how to diagnose the problem yourself. — jfriend00, Mar 21 '16 at 17:31

score 2 · Accepted Answer · answered Mar 21 '16 at 17:26

2

When you access a url using the browser , the browser will send a request for the favicon, then send another request for the content, that's why you are seeing two requests !

Use PostMan and request the same url , you should see only one request.

answered Mar 21 '16 at 17:26

Bassam Rubaye

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score 2 · Answer 3 · edited May 23 '17 at 12:07

2

No mistake--this is normal! Your browser makes multiple requests. There's a similar answer at nodejs - http.createServer seems to call twice.

Hope you're having fun learning node.js!

edited May 23 '17 at 12:07

Community

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1

answered Mar 21 '16 at 17:27

hxlnt

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7
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nodejs - why does my async function run twice?

3 Answers3