connect() failed (111: Connection refused) while connecting to upstream

Question

I am hosting my Rails app on Rackspace with nginx webserver.

When calling any Rails API, I see this message in /var/log/nginx/error.log: *49 connect() failed (111: Connection refused) while connecting to upstream, client: 10.189.254.5, server: , request: "POST /api/v1/users/sign_in HTTP/1.1", upstream: "http://127.0.0.1:3001/api/v1/users/sign_in", host: "anthemapp.com"

1. What is the upstream block?
2. What is /etc/nginx/sites-available/default? Is this where I can configure this?
3. Why am I receiving the error above?

I spent several hours with 5-6 different Rackspace tech people (they didn't know how to resolve this). This all started when I took the server into rescue mode and followed the steps here: https://community.rackspace.com/products/f/25/t/69. Once I came out of rescue mode and rebooted the server, I started receiving the error I am writing about. Tnx!

Heredity

Answer 1

Nginx is a reverse proxy server - its role on your server is to accept HTTP requests and proxy them to another process on the same host. The "upstream" that the error message is talking about is referring to the bit in nginx's configuration (part of which is the /etc/nginx/sites-available/default file) that tells it where to send incoming requests. The error message you're seeing indicates that nginx received a request, but couldn't send it to the other process it was supposed to.

When your server rebooted, the nginx process started back up, but your Rails process -- the one that's meant to be listening on port 3001 -- did not!

How you restart the Rails process depends on the way that you started it before and the way your server is configured. It may be as simple as cd'ing into your Rails application's directory on the server and running:

rails server -b 127.0.0.1 -p 3001 -e production -d

...but, to prevent problems like this from happening in the future (and to improve the performance of your Rails app!), it would be better to use some kind of production-ready Rails application server. I would recommend using Phusion Passenger because it's the most turn-key solution -- their user's guide for nginx describes installation and configuration -- but there are plenty of alternatives. There's a great writeup of what your options are, what they all mean, and how they relate on the top answer of this StackOverflow question.

Theresatherese

Thans Ash! I'm using Thin as my app server. How can I ensure that Thin is running? How do I debug the configuration between nginx and Thin? – Heredity

Ah, good, you're using something other than WEBrick already! I haven't used Thin specifically myself, but a quick ps -ef | grep thin should show you if any thin processes are running. – Theresatherese

Also: it looks like sudo thin install will actually write you an /etc/init.d script that will make sure thin runs on boot. That's handy! Here's a blog post I found that talks about it a little: jordanhollinger.com/2011/04/22/how-to-use-thin-effectivly – Theresatherese

Answer 2

In my case I need to run:

bundle install
bundle update

and then:

sudo stop puma-manager
sudo start puma-manager

Forage

Answer 3

This is resolved when I run below command

cap production puma:restart

It happens sometimes if we are switching ruby version on the production

Adrianeadrianna