feature: allow a configurable backend address

docker-compose.dev.yml

@@ -31,6 +31,8 @@ services:
     ports:
       - "8001:80"
     restart: unless-stopped
+    environment:
+      BACKEND_ADDR: ${BACKEND_ADDR:-http://backend:8000}
 
   mailpit:
     image: axllent/mailpit:latest

docker-compose.e2e.yml

@@ -35,6 +35,8 @@ services:
     depends_on:
       backend:
         condition: service_healthy
+    environment:
+      BACKEND_ADDR: http://backend:8000
 
   test-runner:
     build:

docker-compose.yml

@@ -17,3 +17,5 @@ services:
     ports:
       - "8001:80"
     restart: unless-stopped
+    environment:
+      BACKEND_ADDR: ${BACKEND_ADDR:-http://backend:8000}

docs/guide/configuration.md

@@ -146,11 +146,19 @@ To opt out entirely:
 TELEMETRY_DISABLED=true
 ```
 
-## Frontend Build
+## Frontend
 
-| Variable | Description | Default |
-|----------|-------------|---------|
-| `PUBLIC_DEFAULT_LOCALE` | Default UI language (`en`, `de`, `zh`, `es`, or `fr`) | `en` |
+### Run Time
+
+| Variable       | Description                                                                                                                        |
+| -------------- | ---------------------------------------------------------------------------------------------------------------------------------- |
+| `BACKEND_ADDR` | Configures the upstream address for the Nginx webserver. For the default `docker-compose.yml` this is set to `http://backend:8000`. **NOTE**: Remove trailing `/` as they might interfere with NGINXs routing behavior. |
+
+### Build Time
+
+| Variable                | Description                                           | Default |
+| ----------------------- | ----------------------------------------------------- | ------- |
+| `PUBLIC_DEFAULT_LOCALE` | Default UI language (`en`, `de`, `zh`, `es`, or `fr`) | `en`    |
 
 ## Import Limits
 

docs/releases.md

@@ -53,6 +53,7 @@ LibrisLog v1.9.0 brings shareable public profile pages, edition grouping and an
 - 🌍 **Localized source names.** Import sources are shown under their translated name in the search progress list and in the edition chips, in all five UI languages
 
 **Improvements**
+- 🌐 Allow a configurable backend address via `BACKEND_ADDR` for setups besides the default `docker-compose.yml`
 - 📌 **Sticky Add Book dialog header.** The dialog title and the close button stay pinned to the top of the window while the content scrolls, so closing the dialog no longer requires scrolling back up after a long list of results
 - 🔍 **Search results report each source.** The progress list names every source that was queried, including those that were skipped and why
 

frontend/Dockerfile

@@ -17,5 +17,7 @@ RUN npm run build
 # Stage 2: serve
 FROM nginx:alpine
 COPY --from=builder /app/build /usr/share/nginx/html
-COPY nginx.conf /etc/nginx/conf.d/default.conf
+COPY nginx.conf.template /etc/nginx/templates/default.conf.template
+COPY docker-entrypoint.d/ /docker-entrypoint.d/
+ENV BACKEND_ADDR=http://backend:8000
 EXPOSE 80

frontend/docker-entrypoint.d/10-warn-backend-addr.sh

@@ -0,0 +1,30 @@
+#!/bin/sh
+# Warns about BACKEND_ADDR values that would break API routing.
+#
+# nginx treats a URI part in proxy_pass (a trailing slash) as a prefix to replace,
+# so "http://backend:8000/" forwards a request for /api/books as /books and every
+# API call returns 404 while nginx itself starts cleanly.
+#
+# The value cannot be corrected here. envsubst only substitutes variables verbatim,
+# and the image runs each script in /docker-entrypoint.d as a separate process, so an
+# export from this script never reaches the later envsubst call. Printing is the only
+# thing that works without replacing the image entrypoint or giving up nginx's
+# startup-time upstream validation.
+#
+# The numbered filename makes this run before 20-envsubst-on-templates.sh.
+
+BACKEND_ADDR="${BACKEND_ADDR-}"
+
+case "$BACKEND_ADDR" in
+    "")
+        echo "librislog: BACKEND_ADDR is empty, so nginx renders an invalid proxy_pass and will not start." >&2
+        echo "librislog: set it to an address such as http://backend:8000." >&2
+        ;;
+    */)
+        echo "librislog: BACKEND_ADDR ends with a slash ('$BACKEND_ADDR')." >&2
+        echo "librislog: nginx replaces the matched location prefix, so /api/books is forwarded as /books and every API call returns 404." >&2
+        echo "librislog: drop the trailing slash." >&2
+        ;;
+esac
+
+exit 0

frontend/nginx.conf → frontend/nginx.conf.template

@@ -7,7 +7,7 @@ server {
 
     # API proxy to backend service inside docker network.
     location /api/ {
-        proxy_pass http://backend:8000;
+        proxy_pass ${BACKEND_ADDR};
         proxy_http_version 1.1;
         proxy_set_header Host $http_host;
         proxy_set_header X-Real-IP $remote_addr;