Troubleshooting 502 Bad Gateway on nginx Using Node.js on Elastic Beanstalk

I started to work with Elastic Beanstalk on AWS recently and ran into an issue when trying to deploy a Node.js app that I thought might be worth sharing. I created a test Node.js and Express application locally that worked fine and I then tried deploying using the Elastic Beanstalk console. Everything appeared to deploy correctly but when I tried accessing my url I received the following error “502 Bad Gateway” on “nginx/1.2.6”.

Unfortunately this error message didn’t give me much to go on, but when I looked in the Elastic Beanstalk log files I saw the following entry:

2013/05/18 13:33:37 [error] 1708#0: *11 connect() failed (111: Connection refused) while connecting to upstream, client: 10.159.27.244, server: , request: "GET / HTTP/1.1", upstream: "http://127.0.0.1:8081/", host: "fitfavorites.elasticbeanstalk.com"

The confusing part of this error message for me was the port number of 8081, that was not the port I was expecting Beanstalk to utilize for my site. Looking at the code that was working locally I realized I had hard coded the port number to 3000. I quickly modified my configuration code with the following snippet. This code allows the application to use either a port setting set in the environment variables or default to 3000 if no port is configured.

var express = require('express');
var app = express();

app.configure(function(){

  app.set('port', process.env.PORT || 3000);
  ....

After re-deploying this to AWS, sure enough my problem disappeared. The one thing that was of interest to me was that I did not have to set an environment variable, it appears that Beanstalk has this set already for me.

I hope this helps anyone else who runs into this same issue. Have fun with Node on Elastic Beanstalk!