How do I configure Nginx proxy_pass Node.js HTTP server via UNIX socket?

Question

I am trying to configure a Nginx server to connect to a Node.js HTTP server via a UNIX domain socket.

The Nginx configuration file:

server { listen 80; location / { proxy_pass http://unix:/tmp/app.socket:/; } } 

(according to http://wiki.nginx.org/HttpProxyModule#proxy_pass)

The Node.js script:

var http = require('http'); http.createServer(function(req, res) { console.log('received request'); req.end('received request\n'); }).listen('/tmp/app.socket'); 

Now, when I try to call

curl http://localhost/ 

I only get the 502 Bad Gateway error page in curl and nothing on the Node.js process.

Am I doing something wrong?

edit:

After trying quanta's solution, the mistake must have to do with the Nginx configuration, since the Node.js process establishes the connection to the socket correctly.

I also tried to configure Nginx this way:

upstream myapp { server unix:/tmp/app.socket; } server { listen 80; location / { proxy_pass http://myapp; } } 

But this didn't work either.

BTW I'm using Nginx v1.0.6.

The following is being written to the error log in Nginx, when I use the second configuration

2011/09/28 13:33:47 [crit] 1849#0: *5 connect() to unix:/tmp/app.socket failed (13: Permission denied) while connecting to upstream, client: 127.0.0.1, server: , request: "GET / HTTP/1.1", upstream: "http://unix:/tmp/app.socket:/", host: "localhost:80" 

Answer 1

chmod 777 /tmp/app.socket

This is a solution but not the solution.

You should probably run both webservers with the same user and/or same group so you don't have to make your socket world read writable. Also I don't see why a socket needs to be executable. So 6 should be enough. i.e:

chmod 0660 /tmp/app.socket 

Answer 2

"502 Bad Gateway" means that Nginx cannot receive response from upstream server. Make sure that you have a process listen on /tmp/app.socket:

# netstat --protocol=unix -nlp | grep app.socket 

Answer 3

I solved it. The error log message I postet above lead me to the answer.

I always started the Node.js process as a normal user, while Nginx was started by root. When Node.js was started, it created the socket with srwxr-xr-x rights. So Nginx could not write to the socket, it could only read from it. This way everything could set up correctly, when the processes got started. But once I called the a web page, Nginx realized that it didn't have the rights to proxy the request to the socket.

The solution was to run

chmod 777 /tmp/app.socket 

Now, everything is ok.

Thank you, anyway!

Answer 4

I know I'm late to the party, but this page came up in a Google search for this exact problem. Running a shell command isn't really an ideal solution for me, and this is how I solved it;

Instead of running chmod manually, you can make Node do it with the 'fs' library after the socket is created:

var fs = require('fs'); var server = http.createServer(...This varies by implementation...); server.listen('/path/to/socket'); server.on('listening', onListening); function onListening() { fs.chmodSync('/path/to/socket', '777'); } 

Obviously if you have other things in your onListening event already, you should just add the call to chmodSync into the existing function.