Docker Compose NGINX Reverse Proxy 502

Question

I have the following setup and cannot for the life of me figure out why I can't connect to the api.

nginx.conf

worker_processes auto;
worker_rlimit_nofile 200000;

events {
  use epoll;
  accept_mutex on;
  multi_accept on;
  worker_connections 1024;
}

http {
  error_log /etc/nginx/error_log.log warn;
  client_max_body_size 20m;

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

    location / {
      proxy_pass http://api:8080/;
    }

    location /health {
      return 200;
      access_log off;
    }
  }
}

docker-compose.yml

version: "3.7"

services:
  nginx:
    container_name: nginx
    image: "nginx:latest"
    ports:
      - "8000:80"
    networks:
      - internal_net
    volumes:
      - ./container/nginx.conf:/etc/nginx/nginx.conf

  api:
    container_name: api
    build:
      context: .
      dockerfile: container/Dockerfile
    expose:
      - "8080"
    networks:
      - internal_net
    depends_on:
      - postgres
    command: ["./wait-for-it.sh", "postgres:5432", "--timeout=60", "--", "./52-server-go"]

  postgres:
    container_name: postgres
    image: "postgres:9.5-alpine"
    expose:
      - "5432"
    networks:
      - internal_net

networks:
  internal_net:
    driver: bridge

volumes:
  container:

My api is set to run on port 8080, when I go into the container and run a curl request against that address it works. According to the compose file, it should be exposing that address to the local compose network that is shared by all services including nginx.

According to the nginx config it should be passing every request (except /health check, which works) to the api service. Instead what is returned is a 502 from nginx.

Where am I mixed up? What did I do wrong?

Answer 1

The issue was actually in my go app. Using golang gorilla/mux, had to change the address:

original (broken)

    // Start server
    address := "127.0.0.1:8080"
    srv := &http.Server{
        Handler:      r,
        Addr:         address,
        WriteTimeout: 15 * time.Second,
        ReadTimeout:  15 * time.Second,
    }

fix

    // Start server
    address := "0.0.0.0:8080"
    srv := &http.Server{
        Handler:      r,
        Addr:         address,
        WriteTimeout: 15 * time.Second,
        ReadTimeout:  15 * time.Second,
    }

I don't know why, but that fixed it.