Use ENTRYPOINT for Nginx runtime substitution

Author: aaronskiba

Dockerfile.production

@@ -142,7 +142,9 @@ HEALTHCHECK --interval=30s --timeout=5s --start-period=5s --retries=3 \
 # nginx stage to serve static assets and proxy requests to api container
 FROM nginx:$NGINX_VERSION AS web
 
-ENV INSTALL_PATH=/usr/src/app
+ENV INSTALL_PATH=/usr/src/app \
+    API_SERVICE_HOST=api \
+    API_SERVICE_PORT=3000
 
 # Create non-root user
 RUN addgroup -g 3000 -S dmpgroup && \
@@ -163,13 +165,14 @@ COPY nginx.conf /etc/nginx/nginx.conf
 RUN chown dmpuser:dmpgroup /etc/nginx/nginx.conf && \
     chmod 664 /etc/nginx/nginx.conf
 
+# Set up an entrypoint script to replace variables dynamically
+COPY nginx-entrypoint.sh /usr/local/bin/entrypoint.sh
+RUN chmod +x /usr/local/bin/entrypoint.sh
+
 USER dmpuser
 
 EXPOSE 80
 
-# Replace environment variables in nginx.conf and overwrite the file
-CMD envsubst '${API_URL}' < /etc/nginx/nginx.conf | tee /etc/nginx/nginx.conf > /dev/null \
-    # Set to read-only after substitution
-    && chmod 644 /etc/nginx/nginx.conf \
-    # Start Nginx in the foreground to keep the container running
-    && exec nginx -g 'daemon off;'
+ENTRYPOINT ["/usr/local/bin/entrypoint.sh"]
+
+CMD ["nginx", "-g", "daemon off;"]

nginx-entrypoint.sh

@@ -0,0 +1,10 @@
+#!/bin/sh
+
+# Replace environment variables in nginx.conf and overwrite the file
+envsubst '${API_SERVICE_HOST} ${API_SERVICE_PORT}' < /etc/nginx/nginx.conf | tee /etc/nginx/nginx.conf > /dev/null
+
+# Set to read-only after substitution
+chmod 644 /etc/nginx/nginx.conf
+
+# Execute the main process
+exec "$@"

nginx.conf

@@ -67,7 +67,7 @@ http {
         }
         # Proxy configuration for API
         location / {
-            proxy_pass ${API_URL};
+            proxy_pass http://${API_SERVICE_HOST}:${API_SERVICE_PORT};
 
             # Standard proxy headers
             proxy_set_header Host $host;