NGINX Load Balancer: [emerg] 1#1: host not found in upstream "server.two:8088" in /etc/nginx/conf.d/alb.conf:27

Question

Trying to build simple example of using NGINX as a load balancer, i am getting the error when starting:

[emerg] 1#1: host not found in upstream "server.two:8088" in /etc/nginx/conf.d/alb.conf:27

I know that this issue can be related to the server which is not running when the upstream is upping.

So my question is -- Is there solution on how to run NGINX servers before upstream is upping? Or is there any solution how it can be fixed in other way?

My env is:

• Win 10
• WSL2
• Docker

docker-compose.yml contains:

version: "3"
services:
  app:
    image: nginx:1.25.2
    container_name: "load_balancer_nginx"
    ports:
      - "80:80"
      - "8000:8000"
    volumes:
      - ../src/:/var/www/html:rw
      - ../nginx/nginx.conf:/etc/nginx/nginx.conf
      - ../nginx/default.conf:/etc/nginx/conf.d/default.conf
      - ../nginx/alb.conf:/etc/nginx/conf.d/alb.conf # Application Load Balancer

alb.conf:

server {
    listen 8000;
    server_name server.one;
    root /var/www/html/server.one/;
    charset utf-8;
    index index.html;
    location / {
        try_files $uri $uri/ =404;
    }
}
server {
    listen 8088;
    server_name server.two;
    root /var/www/html/server.two/;
    charset utf-8;
    index index.html;
    location / {
        try_files $uri $uri/ =404;
    }
}
upstream all {
    server server.one:8000;
    server server.two:8088;
}
server {
    listen 80;
    server_name magento_alb.loc;
    absolute_redirect off;
    location / {
        proxy_pass http://all/;
        proxy_pass_request_headers on;
        proxy_set_header Host $host;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_redirect off;
        proxy_intercept_errors on;
        proxy_cache off;
    }
}

default.conf:

#nothing. just to rewrite the existing one.

nginx.conf:

events {}

http {
  include /etc/nginx/conf.d/*.conf;
}

a) Trying to start docker container without errors, But i am facing with errors.

b) have tried to use the variable but also without any success( still getting the same error ) set $backend_servers all; proxy_pass http://$backend_servers;

c) have tried to use the map -- no success ( i am getting the same error ) map $scheme $server_two { default server.two:8088; } upstream all { server server.one:8000; server $server_two; }

d) Used the fail_timeout & max_fails -- the same error upstream all { server server.one:8000 fail_timeout=999s max_fails=999999; server server.two:8088 fail_timeout=999s max_fails=999999; }