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502 Bad Gateway when using reverse proxy with Docker and Nginx

I have searched StackOverflow for my problem but I always seem to be hitting the 502 Bad Gateway with my Nginx Docker configuration. I am trying to access pgadmin4 using my domain mydomain.com/pgadmin instead of mydomain.com:8060 where 8060 is the port exposed by it’s docker container. My docker-compose.yml file looks like this:

version: '3.5'

services:
  reverse-proxy:
    image: nginx:1.19.6
    restart: always
    ports:
      - "80:80"
      - "443:443"
        
  postgres:
    image: postgres:12
    ports:
      - "5432:5432"
        
  pgadmin:
    image: dpage/pgadmin4
    depends_on:
      - postgres
    ports:
      - "8060:80"
      
networks:
  default:
    external:
      name: defaultnetwork

The default.conf file of my nginx container looks like this:

upstream pgadmin {
    server 127.0.0.1:8060;
}

server {
    listen       80;
    listen  [::]:80;
    server_name  mydomain.com;
    
    root   /usr/share/nginx/html;
    index  index.html index.htm;
    
    location /pgadmin {
        proxy_pass http://pgadmin;
    } 
}

With this configuration, I keep getting the 502 Bad Gateway error. Could someone kindly point to me where I am going wrong. I would really appreciate it.

Thanks.

[EDIT] This is from the docker logs:

2021/02/03 08:07:42 [error] 23#23: *2 connect() failed (111: Connection refused) while connecting to upstream, client: ***.***.***.***, server: mydomain.com, request: "GET /pgadmin HTTP/1.1", upstream: "http://127.0.0.1:8082/pgadmin", host: "mydomain.com"
Tags:

2

Answers


  1. 0

    The 502 problem comes from the loopback IP here:

    upstream pgadmin {
    server 127.0.0.1:8060;
    }

    127.0.0.1 or localhost for the NGINX container is the NGINX container itself. You should use the name of the service instead:

    upstream pgadmin {
    server pgadmin:8060;
}

    Name of the service comes from the docker-compose.yml:

    services:
  pgadmin: # <- this
    image: dpage/pgadmin4

    If you hit 404 after these changes, this is because you have to change base path of the application. Try using this config:

        location /pgadmin/ {
        proxy_set_header X-Script-Name /pgadmin;
        proxy_set_header Host $host;
        proxy_pass http://pgadmin;
        proxy_redirect off;
    }
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  2. 0

    Since your containers are working in the same network, you should access the Pgadmin container via 80th port from your Nginx container.

    You should replace this line server 127.0.0.1:8060 with server pgadmin:80 in your Nginx config.

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