Improve: smaller image and one nginx worker

Dockerfile

@@ -8,24 +8,33 @@ COPY nginx/ ./nginx/
 COPY scripts/bump-cache-busting.js ./scripts/bump-cache-busting.js
 RUN node scripts/bump-cache-busting.js
 
-FROM node:24-alpine@sha256:44fce696f38ba8c987c4db89954051000bbd05ffd8d8659ba15ed4a8602e937f
+FROM node:24-alpine@sha256:44fce696f38ba8c987c4db89954051000bbd05ffd8d8659ba15ed4a8602e937f AS base
 
-LABEL org.opencontainers.image.title="Stackyard" \
-      org.opencontainers.image.description="Self-hosted homelab dashboard" \
-      org.opencontainers.image.source="https://github.com/SandObserver/stackyard" \
-      org.opencontainers.image.licenses="Apache-2.0"
-
-# No package manager in the runtime image. The check fails the build if a base
-# image change makes a path stop matching.
+# No package manager and no C headers in the runtime image. The check fails the
+# build if a base image change makes a path stop matching.
 RUN rm -rf /usr/local/lib/node_modules/npm \
            /usr/local/lib/node_modules/corepack \
+           /usr/local/include/node \
            /opt/yarn-* && \
     rm -f /usr/local/bin/npm /usr/local/bin/npx /usr/local/bin/corepack \
           /usr/local/bin/yarn /usr/local/bin/yarnpkg && \
     if command -v npm || command -v npx || command -v yarn || command -v corepack; then \
       echo "a package manager survived removal; check the base image layout" >&2; exit 1; \
     fi && \
-    node -e "process.exit(0)"
+    if [ -n "$(find / -xdev -name node.h)" ]; then \
+      echo "the C headers survived removal; check the base image layout" >&2; exit 1; \
+    fi && \
+    node -e "process.exit(0)" && \
+    find / -xdev \( -path /proc -o -path /sys -o -path /dev \) -prune -o -type d -exec touch -r /usr/local/bin/node {} +
+
+FROM scratch
+COPY --from=base / /
+ENV PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
+
+LABEL org.opencontainers.image.title="Stackyard" \
+      org.opencontainers.image.description="Self-hosted homelab dashboard" \
+      org.opencontainers.image.source="https://github.com/SandObserver/stackyard" \
+      org.opencontainers.image.licenses="Apache-2.0"
 
 # Keep `apk upgrade` first. The base image is pinned by digest and gets no
 # security updates without it.
@@ -41,6 +50,8 @@ RUN echo "packages upgraded for ${APP_VERSION}" && \
     apk upgrade --no-cache && \
     apk add --no-cache nginx supervisor && \
     rm -f /etc/nginx/conf.d/default.conf /etc/nginx/http.d/default.conf && \
+    sed -i 's/^worker_processes auto;$/worker_processes 1;/' /etc/nginx/nginx.conf && \
+    grep -qx 'worker_processes 1;' /etc/nginx/nginx.conf && \
     mkdir -p /var/log/nginx /var/log/supervisor /var/lib/nginx /run/nginx && \
     # Users mount volumes here. Owned by node so the API can write config and
     # icons without running as root.

api/test/nginx-config.test.js

@@ -480,6 +480,12 @@ test('the image stamps assets itself, so a locally built image is not pinned to
   );
 });
 
+test('the image runs one nginx worker, not one per host core', () => {
+  const dockerfile = fs.readFileSync(path.join(__dirname, '../../Dockerfile'), 'utf8');
+  assert.match(dockerfile, /sed -i 's\/\^worker_processes auto;\$\/worker_processes 1;\/' \/etc\/nginx\/nginx\.conf/);
+  assert.match(dockerfile, /grep -qx 'worker_processes 1;' \/etc\/nginx\/nginx\.conf/);
+});
+
 /* ── the API policy ───────────────────────────────────────────────────────── */
 
 /* /api/ sets its own headers, so the server-level policy does not reach it. The

test/repo/image-hardening.test.js

@@ -6,8 +6,13 @@ const path = require('node:path');
 const root = path.join(__dirname, '..', '..');
 const dockerfile = fs.readFileSync(path.join(root, 'Dockerfile'), 'utf8');
 
-test('the Dockerfile removes npm, corepack and yarn', () => {
-  for (const target of ['/usr/local/lib/node_modules/npm', '/usr/local/lib/node_modules/corepack', '/opt/yarn-*']) {
+test('the Dockerfile removes npm, corepack, yarn and the C headers', () => {
+  for (const target of [
+    '/usr/local/lib/node_modules/npm',
+    '/usr/local/lib/node_modules/corepack',
+    '/opt/yarn-*',
+    '/usr/local/include/node',
+  ]) {
     assert.ok(dockerfile.includes(target), `${target} is no longer removed`);
   }
   for (const bin of ['/usr/local/bin/npm', '/usr/local/bin/npx', '/usr/local/bin/corepack', '/usr/local/bin/yarn']) {
@@ -18,6 +23,12 @@ test('the Dockerfile removes npm, corepack and yarn', () => {
 test('the removal is verified inside the build', () => {
   assert.match(dockerfile, /if command -v npm \|\| command -v npx \|\| command -v yarn \|\| command -v corepack; then/);
   assert.match(dockerfile, /a package manager survived removal/);
+  assert.match(dockerfile, /if \[ -n "\$\(find \/ -xdev -name node\.h\)" \]; then/);
+  assert.match(dockerfile, /the C headers survived removal/);
+});
+
+test('the copied base layer is the same for one base digest', () => {
+  assert.match(dockerfile, /-type d -exec touch -r \/usr\/local\/bin\/node \{\} \+$/m);
 });
 
 test('node itself is still checked to work afterwards', () => {
@@ -123,7 +134,11 @@ test('the upgrade cannot be served from a cache across releases', () => {
 /* The API runs as node. Code it owns, it can rewrite, and the change survives a
    restart. */
 test('the API cannot rewrite its own code', () => {
-  const runtime = dockerfile.split(/^FROM /m).pop();
+  const runtime = dockerfile
+    .split(/^FROM /m)
+    .slice(1)
+    .filter(stage => !/^\S+ AS assets$/m.test(stage.split('\n')[0]))
+    .join('\n');
   const copies = runtime.split('\n').filter(l => /^COPY .*\/app\//.test(l));
   assert.ok(copies.length > 0);
   for (const line of copies) assert.doesNotMatch(line, /--chown/, line);

test/repo/readme-dependencies.test.js

@@ -24,5 +24,6 @@ test('the API declares no npm dependencies', () => {
 test('the image installs nginx and supervisor and no other package', () => {
   const adds = [...read('Dockerfile').matchAll(/apk add\s+((?:--\S+\s+)*)([^&\\\n]+)/g)].map(m => m[2].trim());
   assert.deepEqual(adds, ['nginx supervisor']);
-  assert.match(read('Dockerfile'), /^FROM node:\d+-alpine@sha256:[0-9a-f]{64}$/m);
+  assert.match(read('Dockerfile'), /^FROM node:\d+-alpine@sha256:[0-9a-f]{64} AS base$/m);
+  assert.match(read('Dockerfile'), /^COPY --from=base \/ \/$/m);
 });

test/repo/supervisord-fatal.test.js

@@ -177,8 +177,10 @@ test('the rest of scripts/ is still kept out of the build context', () => {
    image would ship build tooling to every user. */
 test('only the supervisor listener reaches the runtime image', () => {
   const runtime = read('Dockerfile')
-    .split(/^FROM node:24-alpine(?:@sha256:[0-9a-f]{64})?$/m)
-    .pop();
+    .split(/^FROM /m)
+    .slice(1)
+    .filter(stage => !/^\S+ AS assets$/m.test(stage.split('\n')[0]))
+    .join('\n');
   const copied = [...runtime.matchAll(/^COPY (?:--\S+ )*(scripts\/\S+)/gm)].map(m => m[1]);
   assert.deepEqual(copied, ['scripts/exit-on-fatal.py']);
 });