Nginx – How to connect node.js backend to NGINX reverse proxy server

nginxnode.js

I know I'm close but I can't seem to connect my node.js app to my NGINX reverse proxy. My node app works locally and my config file tests ok. It doesn't connect after it's been uploaded to Digital Ocean.

The error is 502 Bad Gateway.

Something is missing and after a couple of hours of googling and testing I still can't find the problem. Thanks so much for any help in advance!

These are the relevant lines from my nginx.conf file.

 server {
        listen        80;
        listen        [::]:80;
        server_name   myDomainName.com;
        root          /www/html;

        location / {
             index       index.html;
        }

        location /proxytest {
            proxy_pass "http://www.myDomainName.com:8080";
        }

    }

This is my node.js test app.

const express = require('express');

const app = express();

app.get('/', (request, response) => {
    response.send('Hello World!');
});

app.listen(8080, () => {
    console.log('Server is up on port 8080');
});

Best Answer

If this is all running a single instance, then typically Nginx wants to talk to a local nodejs service running on port 8080, and so localhost would be more usual than www.myDomainName.com

This would normally be something like

 location /proxytest {
            proxy_pass http://localhost:8080;
        }

Whatever you set the proxy_pass value to, you should check that address is available from the nginx box command line.

# curl -I  http://localhost:8080
HTTP/1.1 200 OK
X-Powered-By: Express
Date: Tue, 06 Feb 2018 02:23:35 GMT
Connection: keep-alive

Also you can check the error log on nginx to see if it reported anything funny.

vi /var/log/nginx/error.log

Other things to try

If you are on an selinux distribution (CentOS, Fedora, RHEL...) try disabling selinux and try the request again

 # setenforce Permissive
 setenforce: SELinux is disabled

Related Solutions

Nginx – How to Set Up as a Caching Reverse Proxy

I don't think that there is a way to explicitly invalidate cached items, but here is an example of how to do the rest. Update: As mentioned by Piotr in another answer, there is a cache purge module that you can use. You can also force a refresh of a cached item using nginx's proxy_cache_bypass - see Cherian's answer for more information.

In this configuration, items that aren't cached will be retrieved from example.net and stored. The cached versions will be served up to future clients until they are no longer valid (60 minutes).

Your Cache-Control and Expires HTTP headers will be honored, so if you want to explicitly set an expiration date, you can do that by setting the correct headers in whatever you are proxying to.

There are lots of parameters that you can tune - see the nginx Proxy module documentation for more information about all of this including details on the meaning of the different settings/parameters: http://nginx.org/r/proxy_cache_path

http {
  proxy_cache_path  /var/www/cache levels=1:2 keys_zone=my-cache:8m max_size=1000m inactive=600m;
  proxy_temp_path /var/www/cache/tmp; 


  server {
    location / {
      proxy_pass http://example.net;
      proxy_cache my-cache;
      proxy_cache_valid  200 302  60m;
      proxy_cache_valid  404      1m;
    }
  }
}

NGINX Redirect – How to Rewrite All HTTP Requests to HTTPS While Maintaining Sub-Domain

Correct way in new versions of nginx

Turn out my first answer to this question was correct at certain time, but it turned into another pitfall - to stay up to date please check Taxing rewrite pitfalls

I have been corrected by many SE users, so the credit goes to them, but more importantly, here is the correct code:

server {
       listen         80;
       server_name    my.domain.com;
       return         301 https://$server_name$request_uri;
}

server {
       listen         443 ssl;
       server_name    my.domain.com;
       # add Strict-Transport-Security to prevent man in the middle attacks
       add_header Strict-Transport-Security "max-age=31536000" always; 

       [....]
}