Merge pull request #2600 from spotify/rugvip/disco

backend: add service discovery interface and implement for single host deployments

plugins/auth-backend/src/service/router.ts

@@ -22,13 +22,16 @@ import { Logger } from 'winston';
 import { createAuthProviderRouter } from '../providers';
 import { Config } from '@backstage/config';
 import { DatabaseKeyStore, TokenFactory, createOidcRouter } from '../identity';
-import { NotFoundError } from '@backstage/backend-common';
+import {
+  NotFoundError,
+  PluginEndpointDiscovery,
+} from '@backstage/backend-common';
 
 export interface RouterOptions {
   logger: Logger;
   database: Knex;
   config: Config;
-  basePath?: string;
+  discovery: PluginEndpointDiscovery;
 }
 
 export async function createRouter(
@@ -38,9 +41,7 @@ export async function createRouter(
   const logger = options.logger.child({ plugin: 'auth' });
 
   const appUrl = options.config.getString('app.baseUrl');
-  const backendUrl = options.config.getString('backend.baseUrl');
-  // TODO(Rugvip): Replace with service discovery of external URL
-  const authUrl = backendUrl + (options.basePath ?? '/api/auth');
+  const authUrl = await options.discovery.getExternalBaseUrl('auth');
 
   const keyDurationSeconds = 3600;
 

plugins/auth-backend/src/service/standaloneServer.ts

@@ -23,6 +23,7 @@ import {
   createServiceBuilder,
   useHotMemoize,
   loadBackendConfig,
+  SingleHostDiscovery,
 } from '@backstage/backend-common';
 
 export interface ServerOptions {
@@ -34,6 +35,7 @@ export async function startStandaloneServer(
 ): Promise<Server> {
   const logger = options.logger.child({ service: 'auth-backend' });
   const config = ConfigReader.fromConfigs(await loadBackendConfig());
+  const discovery = SingleHostDiscovery.fromConfig(config);
 
   const database = useHotMemoize(module, () => {
     const knex = Knex({
@@ -52,6 +54,7 @@ export async function startStandaloneServer(
     logger,
     config,
     database,
+    discovery,
   });
 
   const service = createServiceBuilder(module)

plugins/proxy-backend/src/service/router.test.ts

@@ -17,16 +17,20 @@
 import { createRouter } from './router';
 import * as winston from 'winston';
 import { ConfigReader } from '@backstage/config';
-import { loadBackendConfig } from '@backstage/backend-common';
+import {
+  loadBackendConfig,
+  SingleHostDiscovery,
+} from '@backstage/backend-common';
 
 describe('createRouter', () => {
   it('works', async () => {
     const logger = winston.createLogger();
     const config = ConfigReader.fromConfigs(await loadBackendConfig());
+    const discovery = SingleHostDiscovery.fromConfig(config);
     const router = await createRouter({
       config,
       logger,
-      pathPrefix: '/proxy',
+      discovery,
     });
     expect(router).toBeDefined();
   });

plugins/proxy-backend/src/service/router.ts

@@ -23,12 +23,12 @@ import createProxyMiddleware, {
 } from 'http-proxy-middleware';
 import { Logger } from 'winston';
 import http from 'http';
+import { PluginEndpointDiscovery } from '@backstage/backend-common';
 
 export interface RouterOptions {
   logger: Logger;
   config: Config;
-  // The URL path prefix that the router itself is mounted as, commonly "/proxy"
-  pathPrefix: string;
+  discovery: PluginEndpointDiscovery;
 }
 
 export interface ProxyConfig extends ProxyMiddlewareConfig {
@@ -76,16 +76,14 @@ export async function createRouter(
 ): Promise<express.Router> {
   const router = Router();
 
+  const externalUrl = await options.discovery.getExternalBaseUrl('proxy');
+  const { pathname: pathPrefix } = new URL(externalUrl);
+
   const proxyConfig = options.config.getOptional('proxy') ?? {};
   Object.entries(proxyConfig).forEach(([route, proxyRouteConfig]) => {
     router.use(
       route,
-      buildMiddleware(
-        options.pathPrefix,
-        options.logger,
-        route,
-        proxyRouteConfig,
-      ),
+      buildMiddleware(pathPrefix, options.logger, route, proxyRouteConfig),
     );
   });
 

plugins/proxy-backend/src/service/standaloneServer.ts

@@ -17,6 +17,7 @@
 import {
   createServiceBuilder,
   loadBackendConfig,
+  SingleHostDiscovery,
 } from '@backstage/backend-common';
 import { Server } from 'http';
 import { Logger } from 'winston';
@@ -37,10 +38,11 @@ export async function startStandaloneServer(
   logger.debug('Creating application...');
 
   const config = ConfigReader.fromConfigs(await loadBackendConfig());
+  const discovery = SingleHostDiscovery.fromConfig(config);
   const router = await createRouter({
     config,
     logger,
-    pathPrefix: '/proxy',
+    discovery,
   });
   const service = createServiceBuilder(module)
     .enableCors({ origin: 'http://localhost:3000' })

plugins/techdocs-backend/src/service/router.ts

@@ -26,7 +26,10 @@ import {
   PublisherBase,
   LocalPublish,
 } from '../techdocs';
-import { resolvePackagePath } from '@backstage/backend-common';
+import {
+  PluginEndpointDiscovery,
+  resolvePackagePath,
+} from '@backstage/backend-common';
 import { Entity } from '@backstage/catalog-model';
 import { DocsBuilder } from './helpers';
 
@@ -35,6 +38,7 @@ type RouterOptions = {
   generators: GeneratorBuilder;
   publisher: PublisherBase;
   logger: Logger;
+  discovery: PluginEndpointDiscovery;
   database?: Knex; // TODO: Make database required when we're implementing database stuff.
   config: Config;
   dockerClient: Docker;
@@ -52,20 +56,25 @@ export async function createRouter({
   config,
   dockerClient,
   logger,
+  discovery,
 }: RouterOptions): Promise<express.Router> {
   const router = Router();
 
   router.get('/docs/:kind/:namespace/:name/*', async (req, res) => {
-    const baseUrl = config.getString('backend.baseUrl');
     const storageUrl = config.getString('techdocs.storageUrl');
 
     const { kind, namespace, name } = req.params;
 
-    const entity = (await (
-      await fetch(
-        `${baseUrl}/api/catalog/entities/by-name/${kind}/${namespace}/${name}`,
-      )
-    ).json()) as Entity;
+    const catalogUrl = await discovery.getBaseUrl('catalog');
+    const triple = [kind, namespace, name].map(encodeURIComponent).join('/');
+
+    const catalogRes = await fetch(`${catalogUrl}/entities/by-name/${triple}`);
+    if (!catalogRes.ok) {
+      catalogRes.body.pipe(res.status(catalogRes.status));
+      return;
+    }
+
+    const entity: Entity = await catalogRes.json();
 
     const docsBuilder = new DocsBuilder({
       preparers,
@@ -80,7 +89,7 @@ export async function createRouter({
       await docsBuilder.build();
     }
 
-    return res.redirect(`${storageUrl}${req.path.replace('/docs', '')}`);
+    res.redirect(`${storageUrl}${req.path.replace('/docs', '')}`);
   });
 
   if (publisher instanceof LocalPublish) {

plugins/techdocs-backend/src/service/standaloneServer.ts

@@ -14,7 +14,10 @@
  * limitations under the License.
  */
 
-import { createServiceBuilder } from '@backstage/backend-common';
+import {
+  createServiceBuilder,
+  SingleHostDiscovery,
+} from '@backstage/backend-common';
 import { Server } from 'http';
 import { Logger } from 'winston';
 import { createRouter } from './router';
@@ -39,6 +42,7 @@ export async function startStandaloneServer(
 ): Promise<Server> {
   const logger = options.logger.child({ service: 'techdocs-backend' });
   const config = ConfigReader.fromConfigs([]);
+  const discovery = SingleHostDiscovery.fromConfig(config);
 
   logger.debug('Creating application...');
   const preparers = new Preparers();
@@ -61,6 +65,7 @@ export async function startStandaloneServer(
     publisher,
     dockerClient,
     config,
+    discovery,
   });
   const service = createServiceBuilder(module)
     .enableCors({ origin: 'http://localhost:3000' })