nginx-proxy uses default host without DEFAULT_HOST set

We use nginx-proxy in front of about 25 containers with different sub-domains each.

If a container dies or is stopped, requests are just redirected to a different (other sub-domain) container.

We would rather expect a blank error page. Why is this happening? DEFAULT_HOST is not set.

docker run
  --name nginx-proxy 
  --restart always 
  --publish 80:80 
  --publish 443:443 
  --volume /system/nginx/proxy.conf:/etc/nginx/conf.d/my_proxy.conf:ro 
  --volume /system/nginx/htpasswd:/etc/nginx/htpasswd 
  --volume /system/certs:/etc/nginx/certs 
  --volume /var/run/docker.sock:/tmp/docker.sock:ro 
  --log-opt max-size=100m --log-opt max-file=1000 
  --detach jwilder/nginx-proxy

docker run 
  --name nginx-crypt 
  --restart always 
  --volumes-from nginx-proxy 
  --volume /var/run/docker.sock:/var/run/docker.sock:ro 
  --env "DEFAULT_EMAIL=[e-mail]" 
  --detach jrcs/letsencrypt-nginx-proxy-companion

docker run \
  --name demo-instance \
  --restart always \
  --env NODE_ENV=production \
  --env CUSTOMER=demo \
  --env VIRTUAL_HOST=demo.domain.tld \
  -d registry.domain.tld:443/system:latest

docker run \
  --name demo2-instance \
  --restart always \
  --env NODE_ENV=production \
  --env CUSTOMER=demo2 \
  --env VIRTUAL_HOST=demo2.domain.tld \
  -d registry.domain.tld:443/system:latest

proxy.conf:

  server_tokens off;
  client_max_body_size 1024m;
  proxy_connect_timeout       300;
  proxy_send_timeout          300;
  proxy_read_timeout          300;
  send_timeout                300;

[bluepuma77]

I am currently toying around with traefik. If the web container for a domain is not present it will automatically respond with a plain 404 instead of an arbitrary site that is listening to a different hostname.

Easy use-case: When multiple clients are on one server and a container dies, then I should not show the website of the competition.

If there is a DEFAULT_HOST functionality, then nginx-proxy should not just use an arbitrary service when the variable is not defined, but rather respond with a 404 or similar.

[junderw]

For now it seems wise to add a small container serving just a 502 page, set it as 502.yourdomain.com and set it as your DEFAULT_HOST.

Since this is the default behavior of nginx, the only way this could really be “fixed” is by making the above process more automated by adding DEFAULT_502 etc. option that will add a default_server which returns 502, and turn it off by default.