feat: add a new system metadata service

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

packages/backend/src/experimental/instanceMetadata.ts

@@ -17,23 +17,33 @@ import {
   coreServices,
   createBackendPlugin,
 } from '@backstage/backend-plugin-api';
+import { instanceMetadataServiceRef } from '@backstage/backend-plugin-api/alpha';
+import Router from 'express-promise-router';
 
-// Example usage of the instance metadata service to log the installed plugins.
+// Example usage of the instance metadata service to log the installed features.
 export default createBackendPlugin({
   pluginId: 'instance-metadata-logging',
   register(env) {
     env.registerInit({
       deps: {
-        instanceMetadata: coreServices.rootInstanceMetadata,
+        instanceMetadata: instanceMetadataServiceRef,
         logger: coreServices.logger,
+        httpRouter: coreServices.rootHttpRouter,
       },
-      async init({ instanceMetadata, logger }) {
-        const plugins = await instanceMetadata.getInstalledPlugins();
+      async init({ instanceMetadata, logger, httpRouter }) {
         logger.info(
-          `Installed plugins on this instance: ${plugins
-            .map(e => e.pluginId)
-            .join(', ')}`,
+          `Installed features on this instance: ${JSON.stringify(
+            instanceMetadata.getInstalledFeatures(),
+          )}`,
         );
+
+        const router = Router();
+
+        router.get('/features/installed', (_, res) => {
+          res.json({ items: instanceMetadata.getInstalledFeatures() });
+        });
+
+        httpRouter.use('/.backstage/instanceInfo', router);
       },
     });
   },

packages/backend/src/experimental/systemMetadata.ts

@@ -0,0 +1,93 @@
+/*
+ * Copyright 2024 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 {
+  BackendFeatureMeta,
+  systemMetadataServiceRef,
+} from '@backstage/backend-plugin-api/alpha';
+import Router from 'express-promise-router';
+
+// Example usage of the instance metadata service to log the installed features.
+export default createBackendPlugin({
+  pluginId: 'system-metadata-logging',
+  register(env) {
+    env.registerInit({
+      deps: {
+        systemMetadata: systemMetadataServiceRef,
+        logger: coreServices.logger,
+        httpRouter: coreServices.rootHttpRouter,
+      },
+      async init({ systemMetadata, logger, httpRouter }) {
+        logger.info(
+          `Instances in this system: ${JSON.stringify(
+            await systemMetadata.listInstances(),
+          )}`,
+        );
+
+        const router = Router();
+
+        router.get('/instances', async (_, res) => {
+          res.json(await systemMetadata.listInstances());
+        });
+
+        router.get('/features/installed', async (_, res) => {
+          const instances = await systemMetadata.listInstances();
+          const featurePromises = await Promise.allSettled(
+            instances.map(async instance => {
+              const response = await fetch(
+                `${instance.url}/.backstage/instanceInfo/features/installed`,
+              );
+              if (response.ok) {
+                return { instance, response: await response.json() };
+              }
+              throw new Error(
+                `Failed to fetch installed features from ${instance.url}`,
+              );
+            }),
+          );
+          const pluginByInstance: Record<string, string[]> = {};
+          for (const result of featurePromises) {
+            if (result.status !== 'fulfilled') {
+              logger.error(
+                `Failed to fetch installed features: ${result.reason}`,
+              );
+              continue;
+            }
+            const instance = result.value.instance;
+            const installedFeatures = result.value.response
+              .items as BackendFeatureMeta[];
+            for (const feature of installedFeatures) {
+              if (feature.type === 'plugin') {
+                if (!pluginByInstance[feature.pluginId]) {
+                  pluginByInstance[feature.pluginId] = [];
+                }
+                pluginByInstance[feature.pluginId].push(
+                  `${instance.url}/api/${feature.pluginId}`,
+                );
+              }
+            }
+          }
+          res.json(pluginByInstance);
+        });
+
+        httpRouter.use('/.backstage/systemInfo', router);
+      },
+    });
+  },
+});

packages/backend/src/index.ts

@@ -19,6 +19,7 @@ import {
   coreServices,
   createBackendFeatureLoader,
 } from '@backstage/backend-plugin-api';
+import { systemMetadataServiceFactory } from '@backstage/backend-defaults/alpha/systemMetadata';
 
 const backend = createBackend();
 
@@ -69,7 +70,9 @@ 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('./instanceMetadata'));
+backend.add(import('./experimental/instanceMetadata'));
+backend.add(import('./experimental/systemMetadata'));
+backend.add(systemMetadataServiceFactory);
 
 backend.add(import('@backstage/plugin-events-backend-module-google-pubsub'));
 backend.add(import('@backstage/plugin-mcp-actions-backend'));