Nginx Reverse Proxy: Throwing 502 Bad Gateway

I was following this tutorial to learn about Reverse Proxy https://www.youtube.com/watch?v=ZmH1L1QeNHk&t=227s

I'm running the docker image like this

sudo docker run -d --name nginx-base -p 80:80 nginx:latest

I was able to edit the default.conf Here is the file

server {
    listen       80;
    listen  [::]:80;
    server_name  localhost;

    #access_log  /var/log/nginx/host.access.log  main;

    location / {
        root   /usr/share/nginx/html;
        index  index.html index.htm;
    }

    location /test {
        proxy_pass http://localhost:8086/test;
    }

    location /home {
        proxy_pass http://localhost:3000;
    }

   location /home/auth {
        proxy_pass http://localhost:3000/auth;
    }

    #error_page  404              /404.html;

    # redirect server error pages to the static page /50x.html
    #
    error_page   500 502 503 504  /50x.html;
    location = /50x.html {
        root   /usr/share/nginx/html;
    }

    # proxy the PHP scripts to Apache listening on 127.0.0.1:80
    #
    #location ~ \.php$ {
    #    proxy_pass   http://127.0.0.1;
    #}

    # pass the PHP scripts to FastCGI server listening on 127.0.0.1:9000
    #
    #location ~ \.php$ {
    #    proxy_pass   http://127.0.0.1;
    #}
    
    # pass the PHP scripts to FastCGI server listening on 127.0.0.1:9000
    #
    #location ~ \.php$ {
    #    root           html;
    #    fastcgi_pass   127.0.0.1:9000;
    #    fastcgi_index  index.php;
    #    fastcgi_param  SCRIPT_FILENAME  /scripts$fastcgi_script_name;
    #    include        fastcgi_params;
    #}
    
    # deny access to .htaccess files, if Apache's document root
    # concurs with nginx's one
    #
    #location ~ /\.ht {
    #    deny  all;
    #}
}
     
    

I get the Nginx Welcome screen, when I go to http://localhost/

But when I try to access http://localhost/test or http://localhost/home

Also, I'm able to access localhost:3000 and localhost:8086/test

Not sure why nginx is throwing 502, did I miss any configuration?

Bad Gateway 502 is typically a sign that your destination server is not responding. I assume your other services are Docker container as well? If that is the case you could try to change localhost to their containername and use Docker-dns. But you need to put all containers in the same network for that to work.

Another thing to try is to reverse your order of routes. If I remember correctly nginx takes the first matching route. In your case / matches every other route so every request is directed to your nginx. But your nginx can't handle /test or /home.

I hope this will help you to find the problem.