Refactor nginx configuration and update README

- Moved BACKEND_URL configuration to the frontend service in the README.
- Added validation for the generated nginx configuration in the entrypoint script.
- Removed fallback nginx configuration copy from the Dockerfile.
- Adjusted nginx template to ensure proper header formatting.

This improves the deployment process and clarifies configuration instructions.

README.md

@@ -122,12 +122,12 @@ When ExcaliDash runs behind Traefik, Nginx, or another reverse proxy, configure
 - `BACKEND_URL` (frontend) tells the Nginx container how to reach the backend from inside Docker/Kubernetes. Override it if your reverse proxy exposes the backend under a different hostname.
 
 ```yaml
-frontend:
-  environment:
-    - BACKEND_URL=excalidash-backend.default.svc.cluster.local:8000
 backend:
   environment:
     - FRONTEND_URL=https://excalidraw.example.com
+frontend:
+  environment:
+    - BACKEND_URL=excalidash-backend.default.svc.cluster.local:8000
 ```
 
 # Development

frontend/Dockerfile

@@ -30,8 +30,6 @@ RUN apk add --no-cache gettext
 
 # Copy nginx config template (will be processed at runtime)
 COPY frontend/nginx.conf.template /etc/nginx/nginx.conf.template
-# Also copy the original as fallback
-COPY frontend/nginx.conf /etc/nginx/nginx.conf
 
 # Copy entrypoint script
 COPY frontend/docker-entrypoint.sh /docker-entrypoint.sh

frontend/docker-entrypoint.sh

@@ -10,6 +10,8 @@ echo "Configuring nginx with BACKEND_URL: ${BACKEND_URL}"
 # Only substitute BACKEND_URL, preserve nginx variables like $http_upgrade
 envsubst '${BACKEND_URL}' < /etc/nginx/nginx.conf.template > /etc/nginx/nginx.conf
 
-# Execute the main command (nginx)
-exec "$@"
+# Validate the generated nginx configuration before starting
+nginx -t -c /etc/nginx/nginx.conf
 
+# Execute the main command (nginx)
+exec "$@"

frontend/nginx.conf.template

@@ -27,7 +27,7 @@ http {
             proxy_pass http://${BACKEND_URL}/;
             proxy_http_version 1.1;
             proxy_set_header Upgrade $http_upgrade;
-            proxy_set_header Connection 'upgrade';
+            proxy_set_header Connection "upgrade";
             proxy_set_header Host $host;
             proxy_cache_bypass $http_upgrade;
             proxy_set_header X-Real-IP $remote_addr;
@@ -71,5 +71,4 @@ http {
             add_header Cache-Control "public, immutable";
         }
     }
-}
-
+}