Handling dynamic IP in Django ALLOWED_HOSTS with nginx - django

Question

I'm having issues with what i believe is my nginx.conf which is causing the instance to be restarted again and again, as the health-checks fail on my managed container service.
I'm running my setup in AWS Lightsail Containers, where I have three containers running:
nginx
django
nextjs
When publishing a new release on my AWS Lightsail instance it runs fine for a few minutes, then I hit a 503 error, which causes the instance to reboot - run a few minutes then reboot again.
Looking at the logs I can see that the health-check failed, and django throws and error saying that I should add the request IP to the allowed hosts:
[28/Aug/2021:13:56:23] Invalid HTTP_HOST header: 'x.x.x.x'. You may need to add 'x.x.x.x' to ALLOWED_HOSTS.
[28/Aug/2021:13:56:23] Bad Request: /health.txt
The problem is that my lightsail container service does not have a static IP (nor do I believe I can get a static IP).
My current nginx.conf is below (feedback is appreciated). My question here is how should I deal with this issue? I feel like setting ALLOWED_HOSTS = ['*'] is not a great approach. Can I hardcode the host for the healthcheck or similar?
nginx.conf:
upstream backend {
server ${BACKEND_HOST}:${BACKEND_PORT};
}
upstream frontend {
server ${FRONTEND_HOST}:${FRONTEND_PORT};
}
server {
listen 80 default_server;
server_name example.com;
server_tokens off;
gzip on;
gzip_proxied any;
gzip_comp_level 4;
gzip_types text/css application/javascript image/svg+xml;
location /robots.txt {
include proxy_params;
proxy_pass http://backend;
}
location /health.txt {
include proxy_params;
proxy_pass http://backend;
}
location /api {
include proxy_params;
proxy_pass http://backend;
}
location /admin {
include proxy_params;
proxy_pass http://backend;
}
location / {
proxy_pass http://frontend;
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection 'upgrade';
proxy_set_header Host $host;
proxy_cache_bypass $http_upgrade;
}
}

Answer 1

I use AWS EC2, to pass the health check I get the ip of the instance dynamically and then I insert it into ALLOWED_HOSTS (I think it should work also for Lightsail Containers):
import requests
def get_instance_ip():
try:
ip = requests.get('http://169.254.169.254/latest/meta-data/local-ipv4').text
except requests.exceptions.ConnectionError:
return None
return ip
AWS_IP = get_ec2_instance_ip()
if AWS_IP is not None:
ALLOWED_HOSTS += [AWS_IP]
You can also create a middleware that always returns a 200 status code for the path used by health check (insert the custom middleware before django.middleware.security.SecurityMiddleware in MIDDLEWARE to avoid Invalid HTTP_HOST header error).