add example router

Signed-off-by: aramissennyeydd <aramis.sennyey@doordash.com>

packages/backend/package.json

@@ -69,7 +69,8 @@
     "@opentelemetry/auto-instrumentations-node": "^0.61.0",
     "@opentelemetry/exporter-prometheus": "^0.54.0",
     "@opentelemetry/sdk-node": "^0.54.0",
-    "example-app": "link:../app"
+    "example-app": "link:../app",
+    "express-promise-router": "^4.1.0"
   },
   "devDependencies": {
     "@backstage/cli": "workspace:^"

packages/backend/src/index.ts

@@ -69,6 +69,7 @@ backend.add(searchLoader);
 backend.add(import('@backstage/plugin-techdocs-backend'));
 backend.add(import('@backstage/plugin-signals-backend'));
 backend.add(import('@backstage/plugin-notifications-backend'));
+backend.add(import('./systemMetadataPlugin'));
 
 backend.add(import('@backstage/plugin-events-backend-module-google-pubsub'));
 backend.add(import('@backstage/plugin-mcp-actions-backend'));

packages/backend/src/systemMetadataPlugin.ts

@@ -0,0 +1,48 @@
+/*
+ * Copyright 2025 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import {
+  coreServices,
+  createBackendPlugin,
+} from '@backstage/backend-plugin-api';
+import Router from 'express-promise-router';
+
+/**
+ * Example plugin that shows how to reveal all installed plugins with the
+ * system metadata API.
+ */
+export default createBackendPlugin({
+  pluginId: 'system-metadata-router',
+  register: reg => {
+    reg.registerInit({
+      deps: {
+        systemMetadata: coreServices.rootSystemMetadata,
+        rootHttpRouter: coreServices.rootHttpRouter,
+      },
+      async init({ systemMetadata, rootHttpRouter }) {
+        const router = Router();
+        router.get('/plugins', async (_, res) => {
+          const plugins = (await systemMetadata.getInstalledPlugins()).toSorted(
+            (a, b) => a.pluginId.localeCompare(b.pluginId),
+          );
+          res.json(plugins);
+        });
+
+        rootHttpRouter.use('/.backstage/systemMetadata', router);
+      },
+    });
+  },
+});