Add Kubernetes Router extension point, add fetcher to custom objects provider

Signed-off-by: Ilya Savich <isavich@box.com>

.changeset/full-needles-drive.md

@@ -0,0 +1,6 @@
+---
+'@backstage/plugin-kubernetes-backend': minor
+'@backstage/plugin-kubernetes-node': minor
+---
+
+Add possibility to extends Kubernetes REST API. Add fetcher to parameters for custom objects provider

plugins/kubernetes-backend/src/plugin.ts

@@ -36,6 +36,9 @@ import {
   kubernetesObjectsProviderExtensionPoint,
   type KubernetesObjectsProviderExtensionPoint,
   KubernetesObjectsProviderFactory,
+  KubernetesRouterExtensionPoint,
+  kubernetesRouterExtensionPoint,
+  KubernetesRouterFactory,
   type KubernetesServiceLocator,
   kubernetesServiceLocatorExtensionPoint,
   type KubernetesServiceLocatorExtensionPoint,
@@ -157,6 +160,24 @@ class AuthStrategy implements KubernetesAuthStrategyExtensionPoint {
   }
 }
 
+class CustomRouter implements KubernetesRouterExtensionPoint {
+  private router: KubernetesRouterFactory | undefined;
+
+  getRouter() {
+    return this.router;
+  }
+
+  addRouter(router: KubernetesRouterFactory) {
+    if (this.router) { 
+      throw new Error(
+        'Multiple Kubernetes routers is not supported at this time',
+      );
+    }
+
+    this.router = router;
+  }
+}
+
 /**
  * This is the backend plugin that provides the Kubernetes integration.
  * @public
@@ -169,6 +190,7 @@ export const kubernetesPlugin = createBackendPlugin({
     const extPointAuthStrategy = new AuthStrategy();
     const extPointFetcher = new Fetcher();
     const extPointServiceLocator = new ServiceLocator();
+    const extPointRouter = new CustomRouter()
 
     env.registerExtensionPoint(
       kubernetesObjectsProviderExtensionPoint,
@@ -190,6 +212,10 @@ export const kubernetesPlugin = createBackendPlugin({
       kubernetesServiceLocatorExtensionPoint,
       extPointServiceLocator,
     );
+    env.registerExtensionPoint(
+      kubernetesRouterExtensionPoint,
+      extPointRouter,
+    );
 
     env.registerInit({
       deps: {
@@ -247,6 +273,7 @@ export const kubernetesPlugin = createBackendPlugin({
             clusterSupplier,
             serviceLocator,
             objectsProvider,
+            customRouter: extPointRouter.getRouter(),
           });
 
           http.use(await router.getRouter());

plugins/kubernetes-backend/src/service/KubernetesInitializer.ts

@@ -209,6 +209,7 @@ export class KubernetesInitializer {
             customResources,
             objectTypesToFetch,
           }),
+        fetcher,
         clusterSupplier,
         serviceLocator,
         customResources,

plugins/kubernetes-backend/src/service/KubernetesRouter.test.ts

@@ -28,6 +28,7 @@ import {
   KubernetesFetcher,
   KubernetesServiceLocator,
   KubernetesCredential,
+  kubernetesRouterExtensionPoint,
 } from '@backstage/plugin-kubernetes-node';
 import {
   HEADER_KUBERNETES_CLUSTER,
@@ -809,4 +810,39 @@ metadata:
       'Unsupported kubernetes.serviceLocatorMethod "unsupported"',
     );
   });
+
+  it('custom router', async () => {
+    const { server } = await startTestBackend({
+      features: [
+        minimalValidConfigService,
+        import('@backstage/plugin-kubernetes-backend'),
+        createBackendModule({
+          pluginId: 'kubernetes',
+          moduleId: 'testRouter',
+          register(env) {
+            env.registerInit({
+              deps: { extension: kubernetesRouterExtensionPoint },
+              async init({ extension }) {
+                extension.addRouter(({ getDefault }) => {
+                  const router = getDefault();
+
+                  router.get('/test', (_req, res) => {
+                    res.json({ status: 'ok' });
+                  });
+
+                  return router;
+                });
+              },
+            });
+          },
+        }),
+      ],
+    });
+    app = server;
+
+    const response = await request(app).get('/api/kubernetes/test');
+
+    expect(response.body).toEqual({ status: 'ok' });
+    expect(response.status).toEqual(200);
+  });
 });

plugins/kubernetes-backend/src/service/KubernetesRouter.ts

@@ -40,7 +40,7 @@ import {
   AuthMetadata,
   KubernetesClustersSupplier,
   KubernetesFetcher,
-  KubernetesObjectsProvider,
+  KubernetesObjectsProvider, KubernetesRouterFactory,
   KubernetesServiceLocator,
 } from '@backstage/plugin-kubernetes-node';
 import { addResourceRoutesToRouter } from '../routes/resourcesRoutes';
@@ -62,6 +62,7 @@ export interface KubernetesEnvironment {
   clusterSupplier: KubernetesClustersSupplier;
   serviceLocator: KubernetesServiceLocator;
   objectsProvider: KubernetesObjectsProvider;
+  customRouter?: KubernetesRouterFactory;
 }
 
 export class KubernetesRouter {
@@ -86,6 +87,7 @@ export class KubernetesRouter {
       catalog,
       discovery,
       httpAuth,
+      customRouter,
     } = this.env;
 
     logger.info('Initializing Kubernetes backend');
@@ -108,7 +110,23 @@ export class KubernetesRouter {
       authStrategyMap,
     );
 
-    return this.buildRouter(
+    return customRouter?.({
+      getDefault: () => this.buildDefaultRouter(
+        objectsProvider,
+        clusterSupplier,
+        catalog,
+        proxy,
+        permissions,
+        httpAuth,
+        authStrategyMap,
+      ),
+      objectsProvider,
+      clusterSupplier,
+      catalog,
+      permissions,
+      httpAuth,
+      authStrategyMap,
+    }) ?? this.buildDefaultRouter(
       objectsProvider,
       clusterSupplier,
       catalog,
@@ -138,7 +156,7 @@ export class KubernetesRouter {
     });
   }
 
-  private buildRouter(
+  private buildDefaultRouter(
     objectsProvider: KubernetesObjectsProvider,
     clusterSupplier: KubernetesClustersSupplier,
     catalog: CatalogService,

plugins/kubernetes-node/src/extensions.ts

@@ -13,7 +13,10 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-import { createExtensionPoint } from '@backstage/backend-plugin-api';
+import {
+  createExtensionPoint,
+  HttpAuthService,
+} from '@backstage/backend-plugin-api';
 import {
   AuthenticationStrategy,
   CustomResource,
@@ -23,6 +26,9 @@ import {
   KubernetesObjectsProvider,
   KubernetesServiceLocator,
 } from '@backstage/plugin-kubernetes-node';
+import type express from 'express';
+import type { CatalogService } from '@backstage/plugin-catalog-node';
+import type { PermissionEvaluator } from '@backstage/plugin-permission-common';
 
 /**
  * A factory function for creating a KubernetesObjectsProvider.
@@ -33,6 +39,7 @@ export type KubernetesObjectsProviderFactory = (opts: {
   getDefault: () => Promise<KubernetesObjectsProvider>;
   clusterSupplier: KubernetesClustersSupplier;
   serviceLocator: KubernetesServiceLocator;
+  fetcher: KubernetesFetcher;
   customResources: CustomResource[];
   objectTypesToFetch?: ObjectToFetch[];
   authStrategy: AuthenticationStrategy;
@@ -168,3 +175,37 @@ export const kubernetesServiceLocatorExtensionPoint =
   createExtensionPoint<KubernetesServiceLocatorExtensionPoint>({
     id: 'kubernetes.service-locator',
   });
+
+/**
+ * A factory function for creating a kubernetes router.
+ *
+ * @public
+ */
+export type KubernetesRouterFactory = (opts: {
+  getDefault: () => express.Router;
+  objectsProvider: KubernetesObjectsProvider;
+  clusterSupplier: KubernetesClustersSupplier;
+  catalog: CatalogService;
+  permissions: PermissionEvaluator;
+  httpAuth: HttpAuthService;
+  authStrategyMap: { [key: string]: AuthenticationStrategy };
+}) => express.Router;
+
+/**
+ * The interface for {@link kubernetesRouterExtensionPoint}.
+ *
+ * @public
+ */
+export interface KubernetesRouterExtensionPoint {
+  addRouter(router: KubernetesRouterFactory): void;
+}
+
+/**
+ * An extension point the exposes the ability to configure a kubernetes service locator.
+ *
+ * @public
+ */
+export const kubernetesRouterExtensionPoint =
+  createExtensionPoint<KubernetesRouterExtensionPoint>({
+    id: 'kubernetes.router',
+  });