feat: add Prometheus metrics shim for Indiekit process monitoring

Preloads metrics-shim.cjs via `node --require` into the Indiekit process
so heap, GC, event loop lag, CPU and handle metrics are exposed at
:9209/metrics for Prometheus scraping. Uses prom-client collectDefaultMetrics.

- Add metrics-shim.cjs (prom-client HTTP server, port 9209)
- Add prom-client ^15.1.3 to dependencies
- Wire --require ./metrics-shim.cjs into start.example.sh and npm serve script
- Grafana: NodeJS Application Dashboard (11159) at console.giersig.eu

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

metrics-shim.cjs

@@ -0,0 +1,45 @@
+'use strict';
+// Prometheus metrics shim — preloaded into the Indiekit process via:
+//   node --require ./metrics-shim.cjs <indiekit cli>
+// Because it runs inside the same process, all metrics (heap, GC, event
+// loop lag, CPU, open handles) reflect the actual Indiekit application.
+//
+// Grafana dashboards: NodeJS Application Dashboard (11159) at
+//   https://console.giersig.eu
+//
+// Config via environment variables (set in .env):
+//   METRICS_BIND_HOST  — defaults to 0.0.0.0
+//   METRICS_PORT       — defaults to 9209
+
+const http = require('http');
+const client = require('prom-client');
+
+const register = new client.Registry();
+client.collectDefaultMetrics({ register });
+
+const host = process.env.METRICS_BIND_HOST || '0.0.0.0';
+const port = parseInt(process.env.METRICS_PORT || '9209', 10);
+
+const server = http.createServer(async (req, res) => {
+  if (req.url === '/metrics') {
+    try {
+      const metrics = await register.metrics();
+      res.setHeader('Content-Type', register.contentType);
+      res.end(metrics);
+    } catch (err) {
+      res.writeHead(500);
+      res.end(String(err));
+    }
+  } else {
+    res.writeHead(404);
+    res.end('Not found\n');
+  }
+});
+
+server.listen(port, host, () => {
+  process.stderr.write(`[metrics] Prometheus metrics at http://${host}:${port}/metrics\n`);
+});
+
+server.on('error', (err) => {
+  process.stderr.write(`[metrics] Server error: ${err.message}\n`);
+});

package.json

@@ -5,7 +5,7 @@
   "main": "index.js",
   "scripts": {
     "postinstall": "xattr -w com.apple.fileprovider.ignore#P 1 node_modules 2>/dev/null || true && node scripts/patch-lightningcss.mjs && node scripts/patch-endpoint-media-scope.mjs && node scripts/patch-endpoint-media-sharp-runtime.mjs && node scripts/patch-frontend-sharp-runtime.mjs && node scripts/patch-endpoint-files-upload-route.mjs && node scripts/patch-endpoint-files-upload-locales.mjs && node scripts/patch-endpoint-activitypub-locales.mjs && node scripts/patch-endpoint-homepage-locales.mjs && node scripts/patch-endpoint-homepage-identity-defaults.mjs && node scripts/patch-federation-unlisted-guards.mjs && node scripts/patch-endpoint-micropub-where-note-visibility.mjs && node scripts/patch-endpoint-podroll-opml-upload.mjs && node scripts/patch-frontend-serviceworker-file.mjs && node scripts/patch-endpoint-comments-locales.mjs && node scripts/patch-endpoint-posts-locales.mjs && node scripts/patch-endpoint-conversations-locales.mjs && node scripts/patch-conversations-collection-guards.mjs && node scripts/patch-indiekit-routes-rate-limits.mjs && node scripts/patch-indiekit-error-production-stack.mjs && node scripts/patch-indieauth-devmode-guard.mjs && node scripts/patch-listening-endpoint-runtime-guards.mjs && node scripts/patch-endpoint-github-changelog-categories.mjs && node scripts/patch-endpoint-github-contributions-log.mjs && node scripts/patch-endpoint-blogroll-feeds-alias.mjs && node scripts/patch-endpoint-posts-uid-lookup.mjs && node scripts/patch-conversations-bluesky-self-filter.mjs && node scripts/patch-conversations-bluesky-cursor-fix.mjs && node scripts/patch-endpoint-micropub-source-filter.mjs && node scripts/patch-syndicate-force-checked-default.mjs && node scripts/patch-syndicate-normalize-syndication-array.mjs && node scripts/patch-endpoint-posts-fetch-diagnostic.mjs && node scripts/patch-micropub-fetch-internal-url.mjs && node scripts/patch-micropub-session-token.mjs && node scripts/patch-indiekit-endpoint-urls-protocol.mjs && node scripts/patch-webmention-sender-hentry-syntax.mjs && node scripts/patch-webmention-sender-retry.mjs && node scripts/patch-webmention-sender-livefetch.mjs && node scripts/patch-webmention-sender-empty-details.mjs && node scripts/patch-bluesky-syndicator-internal-url.mjs && node scripts/patch-ap-skip-draft-syndication.mjs",
-    "serve": "export NODE_ENV=${NODE_ENV:-production} INDIEKIT_DEBUG=${INDIEKIT_DEBUG:-0} && node scripts/preflight-production-security.mjs && node scripts/preflight-mongo-connection.mjs && node scripts/preflight-activitypub-rsa-key.mjs && node scripts/preflight-activitypub-profile-urls.mjs && node scripts/patch-lightningcss.mjs && node scripts/patch-endpoint-media-scope.mjs && node scripts/patch-endpoint-media-sharp-runtime.mjs && node scripts/patch-frontend-sharp-runtime.mjs && node scripts/patch-endpoint-files-upload-route.mjs && node scripts/patch-endpoint-files-upload-locales.mjs && node scripts/patch-endpoint-activitypub-locales.mjs && node scripts/patch-endpoint-homepage-locales.mjs && node scripts/patch-endpoint-homepage-identity-defaults.mjs && node scripts/patch-federation-unlisted-guards.mjs && node scripts/patch-endpoint-micropub-where-note-visibility.mjs && node scripts/patch-endpoint-podroll-opml-upload.mjs && node scripts/patch-frontend-serviceworker-file.mjs && node scripts/patch-endpoint-comments-locales.mjs && node scripts/patch-endpoint-posts-locales.mjs && node scripts/patch-endpoint-conversations-locales.mjs && node scripts/patch-conversations-collection-guards.mjs && node scripts/patch-indiekit-routes-rate-limits.mjs && node scripts/patch-indiekit-error-production-stack.mjs && node scripts/patch-indieauth-devmode-guard.mjs && node scripts/patch-listening-endpoint-runtime-guards.mjs && node scripts/patch-endpoint-github-changelog-categories.mjs && node scripts/patch-endpoint-github-contributions-log.mjs && node scripts/patch-microsub-reader-ap-dispatch.mjs && node scripts/patch-microsub-compose-draft-guard.mjs && node scripts/patch-endpoint-blogroll-feeds-alias.mjs && node scripts/patch-endpoint-posts-uid-lookup.mjs && node scripts/patch-conversations-bluesky-self-filter.mjs && node scripts/patch-conversations-bluesky-cursor-fix.mjs && node scripts/patch-endpoint-micropub-source-filter.mjs && node scripts/patch-syndicate-force-checked-default.mjs && node scripts/patch-syndicate-normalize-syndication-array.mjs && node scripts/patch-endpoint-posts-fetch-diagnostic.mjs && node scripts/patch-micropub-fetch-internal-url.mjs && node scripts/patch-micropub-session-token.mjs && node scripts/patch-indiekit-endpoint-urls-protocol.mjs && node scripts/patch-webmention-sender-hentry-syntax.mjs && node scripts/patch-webmention-sender-retry.mjs && node scripts/patch-webmention-sender-livefetch.mjs && node scripts/patch-webmention-sender-empty-details.mjs && node scripts/patch-bluesky-syndicator-internal-url.mjs && node scripts/patch-ap-skip-draft-syndication.mjs && node node_modules/@indiekit/indiekit/bin/cli.js serve --config indiekit.config.mjs",
+    "serve": "export NODE_ENV=${NODE_ENV:-production} INDIEKIT_DEBUG=${INDIEKIT_DEBUG:-0} && node scripts/preflight-production-security.mjs && node scripts/preflight-mongo-connection.mjs && node scripts/preflight-activitypub-rsa-key.mjs && node scripts/preflight-activitypub-profile-urls.mjs && node scripts/patch-lightningcss.mjs && node scripts/patch-endpoint-media-scope.mjs && node scripts/patch-endpoint-media-sharp-runtime.mjs && node scripts/patch-frontend-sharp-runtime.mjs && node scripts/patch-endpoint-files-upload-route.mjs && node scripts/patch-endpoint-files-upload-locales.mjs && node scripts/patch-endpoint-activitypub-locales.mjs && node scripts/patch-endpoint-homepage-locales.mjs && node scripts/patch-endpoint-homepage-identity-defaults.mjs && node scripts/patch-federation-unlisted-guards.mjs && node scripts/patch-endpoint-micropub-where-note-visibility.mjs && node scripts/patch-endpoint-podroll-opml-upload.mjs && node scripts/patch-frontend-serviceworker-file.mjs && node scripts/patch-endpoint-comments-locales.mjs && node scripts/patch-endpoint-posts-locales.mjs && node scripts/patch-endpoint-conversations-locales.mjs && node scripts/patch-conversations-collection-guards.mjs && node scripts/patch-indiekit-routes-rate-limits.mjs && node scripts/patch-indiekit-error-production-stack.mjs && node scripts/patch-indieauth-devmode-guard.mjs && node scripts/patch-listening-endpoint-runtime-guards.mjs && node scripts/patch-endpoint-github-changelog-categories.mjs && node scripts/patch-endpoint-github-contributions-log.mjs && node scripts/patch-microsub-reader-ap-dispatch.mjs && node scripts/patch-microsub-compose-draft-guard.mjs && node scripts/patch-endpoint-blogroll-feeds-alias.mjs && node scripts/patch-endpoint-posts-uid-lookup.mjs && node scripts/patch-conversations-bluesky-self-filter.mjs && node scripts/patch-conversations-bluesky-cursor-fix.mjs && node scripts/patch-endpoint-micropub-source-filter.mjs && node scripts/patch-syndicate-force-checked-default.mjs && node scripts/patch-syndicate-normalize-syndication-array.mjs && node scripts/patch-endpoint-posts-fetch-diagnostic.mjs && node scripts/patch-micropub-fetch-internal-url.mjs && node scripts/patch-micropub-session-token.mjs && node scripts/patch-indiekit-endpoint-urls-protocol.mjs && node scripts/patch-webmention-sender-hentry-syntax.mjs && node scripts/patch-webmention-sender-retry.mjs && node scripts/patch-webmention-sender-livefetch.mjs && node scripts/patch-webmention-sender-empty-details.mjs && node scripts/patch-bluesky-syndicator-internal-url.mjs && node scripts/patch-ap-skip-draft-syndication.mjs && node --require ./metrics-shim.cjs node_modules/@indiekit/indiekit/bin/cli.js serve --config indiekit.config.mjs",
     "test": "echo \"Error: no test specified\" && exit 1"
   },
   "keywords": [],
@@ -51,6 +51,7 @@
     "@rmdes/indiekit-syndicator-indienews": "^1.0.1",
     "dotenv": "^17.3.1",
     "mongodb": "^7.1.0",
-    "node-gyp": "^12.2.0"
+    "node-gyp": "^12.2.0",
+    "prom-client": "^15.1.3"
   }
 }

start.example.sh

@@ -57,7 +57,7 @@ for patch in scripts/patch-*.mjs; do
   "${NODE_BIN}" "$patch"
 done
 
-"${NODE_BIN}" node_modules/@indiekit/indiekit/bin/cli.js serve --config indiekit.config.mjs &
+"${NODE_BIN}" --require ./metrics-shim.cjs node_modules/@indiekit/indiekit/bin/cli.js serve --config indiekit.config.mjs &
 INDIEKIT_PID="$!"
 
 # Webmention sender — polls every N seconds (see @rmdes/indiekit-endpoint-webmention-sender README)