502 Bad Gateway when uploading files (NGINX and NodeJS)

Hey Guys. Please help me out, I am pulling out my hair in frustration trying to fix this. So here is the issue. I am developing an app where the user can upload files. While the backend call seems to work fine, the call when uploading files returns a 502 Bad Gateway message.

The files actually get uploaded but the error message comes up. I think it has something to do with my nginx config so I am hoping you guys can point out where I am going wrong.

Here is the nginx error log message

[error] 3807#3807: *138 connect() failed (111: Connection refused) while connecting to upstream, client:, server:, request: "GET /users/files/5218de9eec94a7bb4467c95219b37b41ec1920420c808d9e11244f8d2a234cd6 HTTP/1.1", upstream: "", host: "", referrer: ""

Here is my nginx.conf file

user www-data;
worker_processes auto;
pid /run/;
include /etc/nginx/modules-enabled/*.conf;

events {
    worker_connections 768;
    # multi_accept on;

http {

    # Basic Settings

    sendfile on;
    tcp_nopush on;
    tcp_nodelay on;
    keepalive_timeout 65;
    types_hash_max_size 2048;
    client_max_body_size 100M;
    # server_tokens off;

    # server_names_hash_bucket_size 64;
    # server_name_in_redirect off;

    include /etc/nginx/mime.types;
    default_type application/octet-stream;

    # SSL Settings

    ssl_protocols TLSv1 TLSv1.1 TLSv1.2; # Dropping SSLv3, ref: POODLE
    ssl_prefer_server_ciphers on;

    # Logging Settings

    access_log /var/log/nginx/access.log;
    error_log /var/log/nginx/error.log;

    # Gzip Settings

    gzip on;

    # gzip_vary on;
    # gzip_proxied any;
    # gzip_comp_level 6;
    # gzip_buffers 16 8k;
    # gzip_http_version 1.1;
    # gzip_types text/plain text/css application/json application/javascript text/xml application/xml application/xml+rss text/javascript;

    # Virtual Host Configs

    include /etc/nginx/conf.d/*.conf;
    include /etc/nginx/sites-enabled/*;

My conf.d folder is empty however I do have specific setting in sites-enabled. Here is my

proxy_cache_path  /etc/nginx/cache levels=1:2 keys_zone=nuxt-cache:25m max_size=1g inactive=60m use_temp_path=off;

server {
    listen 80;
    listen [::]:80;
    return 301 https://$server_name$request_uri;

server {
    index index.html;

    root /opt/siena/App-Web-Nuxt/dist;

    listen [::]:443 ssl ipv6only=on;
    listen 443 ssl;
    ssl_certificate /etc/letsencrypt/live/; # managed by Certbot
    ssl_certificate_key /etc/letsencrypt/live/; # managed by Certbot
    include /etc/letsencrypt/options-ssl-nginx.conf;
    ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem;

    location / {
        try_files $uri $uri/index.html $uri.html;


server {

    listen [::]:443 ssl;
    listen 443 ssl;
    ssl_certificate /etc/letsencrypt/live/; # managed by Certbot
    ssl_certificate_key /etc/letsencrypt/live/; # managed by Certbot
    include /etc/letsencrypt/options-ssl-nginx.conf;
    ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem;

    location / {
        # more_set_headers 'Access-Control-Allow-Origin: *';
        # more_set_headers 'Access-Control-Allow-Methods: GET,POST,OPTIONS,DELETE,PUT';
        # more_set_headers 'Access-Control-Allow-Headers:DNT,X-Mx-ReqToken,Keep-Alive,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type,Authorization';

        # Simple requests (simples to fix CORS)
        if ($request_method ~* "(GET|POST)") {
            more_set_headers "Access-Control-Allow-Origin:  *";

        # Preflighted requests
        if ($request_method = OPTIONS ) {
            more_set_headers "Access-Control-Allow-Origin:  *";
            more_set_headers "Access-Control-Allow-Methods: GET, POST, OPTIONS, HEAD";
            more_set_headers "Access-Control-Allow-Headers: Authorization, Origin, X-Requested-With, Content-Type, Accept";
            return 204;

        proxy_read_timeout 300s;
        proxy_connect_timeout 75s;
        proxy_redirect off;

I am a total noob when it comes to this stuff. Any help would be so much appreciated.

Any more question about the system and the configuration please let me know.

Thanks in Advance.

Submit an answer

This textbox defaults to using Markdown to format your answer.

You can type !ref in this text area to quickly search our full set of tutorials, documentation & marketplace offerings and insert the link!

Sign In or Sign Up to Answer

These answers are provided by our Community. If you find them useful, show some love by clicking the heart. If you run into issues leave a comment, or add your own answer to help others.

Bobby Iliev
Site Moderator
Site Moderator badge
August 21, 2020
Accepted Answer

Hi there @lnbandeira,

What I could suggest starting with is to check your Nginx error log. There you will be able to see the actual error rather than the generic 502 error.

In order to check your error log you can run the following command:

  1. tail -100 /var/log/nginx/error.log

Feel free to share the errors here so that I could try to advise you further.

Also as a side note, here is also a quick video on how to deploy Node.js with PM2, Nginx as a reverse proxy, and Cloudflare for SSL termination:

Regards, Bobby

Try DigitalOcean for free

Click below to sign up and get $200 of credit to try our products over 60 days!

Sign up

Featured on Community

Get our biweekly newsletter

Sign up for Infrastructure as a Newsletter.

Hollie's Hub for Good

Working on improving health and education, reducing inequality, and spurring economic growth? We'd like to help.

Become a contributor

Get paid to write technical tutorials and select a tech-focused charity to receive a matching donation.

Welcome to the developer cloud

DigitalOcean makes it simple to launch in the cloud and scale up as you grow — whether you're running one virtual machine or ten thousand.

Learn more
DigitalOcean Cloud Control Panel