nginx.conf

worker_processes auto;

events {
  worker_connections 1024;
}

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

  sendfile on;

  gzip on;
  gzip_comp_level 2;
  gzip_min_length 1000;
  gzip_proxied any;
  gzip_types
    text/plain
    text/css
    text/xml
    text/javascript
    application/json
    application/javascript
    application/x-javascript
    application/xml
    application/xml+rss
    application/xhtml+xml
    application/vnd.ms-fontobject
    application/x-font-ttf
    font/opentype
    image/svg+xml
    image/x-icon;

  server {
    listen 80 default_server;
    listen [::]:80 default_server;
    root /usr/share/nginx/html;
    index index.html;

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

    location /api {
      proxy_pass http://app:9000;
      proxy_set_header Host $host;
      proxy_set_header X-Real-IP $remote_addr;
      proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
      proxy_set_header X-Forwarded-Proto $scheme;
    }

    location /socket.io/ {
      proxy_pass http://app:3000;
      proxy_http_version 1.1;
      proxy_set_header Upgrade $http_upgrade;
      proxy_set_header Connection "Upgrade";
    }

    error_page 500 502 503 504 /50x.html;
    location = /50x.html {
      root /usr/share/nginx/html;
    }
  }
}