Change the health gateway to use the status API (#160125)

## Summary

Follow-up of https://github.com/elastic/kibana/pull/159768
Related to https://github.com/elastic/kibana/issues/158910

Change the health-gateway behavior to hit the `/api/status` endpoint
instead of just the root `/` path. This was made possible by
https://github.com/elastic/kibana/pull/159768, as we now always return
the correct http code from the status endpoint even for unauthenticated
requests.

packages/kbn-health-gateway-server/src/kibana/handlers/index.ts

@@ -6,4 +6,4 @@
  * Side Public License, v 1.
  */
 
-export { RootRoute } from './root';
+export { StatusHandler } from './status';

packages/kbn-health-gateway-server/src/kibana/handlers/status.test.ts

@@ -8,12 +8,13 @@
 
 import { Server } from '@hapi/hapi';
 import { duration } from 'moment';
+import { URL } from 'url';
 import fetch, { Response } from 'node-fetch';
 import { loggerMock, MockedLogger } from '@kbn/logging-mocks';
 import type { KibanaConfig } from '../kibana_config';
-import { RootRoute } from './root';
+import { StatusHandler } from './status';
 
-describe('RootRoute', () => {
+describe('StatusHandler', () => {
   let kibanaConfig: KibanaConfig;
   let logger: MockedLogger;
   let server: Server;
@@ -30,7 +31,11 @@ describe('RootRoute', () => {
     logger = loggerMock.create();
 
     server = new Server();
-    server.route(new RootRoute(kibanaConfig, logger));
+    server.route({
+      method: 'GET',
+      path: '/',
+      handler: new StatusHandler(kibanaConfig, logger).handler,
+    });
     await server.initialize();
   });
 
@@ -248,5 +253,49 @@ describe('RootRoute', () => {
         })
       );
     });
+
+    it('should call the host with the correct path', async () => {
+      kibanaConfig.hosts.splice(0, kibanaConfig.hosts.length);
+      kibanaConfig.hosts.push('http://localhost:5601', 'http://localhost:5602');
+
+      (fetch as jest.MockedFunction<typeof fetch>).mockResolvedValue(new Response('', ok));
+
+      await server.inject({
+        method: 'get',
+        url: '/',
+      });
+
+      expect(fetch).toHaveBeenCalledTimes(2);
+      expect(fetch).toHaveBeenCalledWith(
+        new URL('http://localhost:5601/api/status'),
+        expect.any(Object)
+      );
+      expect(fetch).toHaveBeenCalledWith(
+        new URL('http://localhost:5602/api/status'),
+        expect.any(Object)
+      );
+    });
+
+    it('should append the status path when path already present on the host', async () => {
+      kibanaConfig.hosts.splice(0, kibanaConfig.hosts.length);
+      kibanaConfig.hosts.push('http://localhost:5601/prefix', 'http://localhost:5602/other/path');
+
+      (fetch as jest.MockedFunction<typeof fetch>).mockResolvedValue(new Response('', ok));
+
+      await server.inject({
+        method: 'get',
+        url: '/',
+      });
+
+      expect(fetch).toHaveBeenCalledTimes(2);
+      expect(fetch).toHaveBeenCalledWith(
+        new URL('http://localhost:5601/prefix/api/status'),
+        expect.any(Object)
+      );
+      expect(fetch).toHaveBeenCalledWith(
+        new URL('http://localhost:5602/other/path/api/status'),
+        expect.any(Object)
+      );
+    });
   });
 });

packages/kbn-health-gateway-server/src/kibana/handlers/status.ts

@@ -6,17 +6,19 @@
  * Side Public License, v 1.
  */
 
-import { capitalize, chain, memoize, pick } from 'lodash';
+import { capitalize, chain, memoize } from 'lodash';
 import { Agent, AgentOptions } from 'https';
 import { URL } from 'url';
-import type { Request, ResponseObject, ResponseToolkit, ServerRoute } from '@hapi/hapi';
+import type { Request, ResponseObject, ResponseToolkit } from '@hapi/hapi';
 import nodeFetch, { Response } from 'node-fetch';
 import type { Logger } from '@kbn/logging';
 import type { KibanaConfig } from '../kibana_config';
 
 type Status = 'healthy' | 'unhealthy' | 'failure' | 'timeout';
 
-interface RootRouteResponse {
+const statusApiPath = '/api/status';
+
+interface StatusRouteResponse {
   status: Status;
   hosts?: HostStatus[];
 }
@@ -27,9 +29,9 @@ interface HostStatus {
   code?: number;
 }
 
-export class RootRoute implements ServerRoute {
+export class StatusHandler {
   private static isHealthy(response: Response) {
-    return RootRoute.isSuccess(response) || RootRoute.isUnauthorized(response);
+    return StatusHandler.isSuccess(response) || StatusHandler.isUnauthorized(response);
   }
 
   private static isUnauthorized({ status, headers }: Response): boolean {
@@ -47,25 +49,20 @@ export class RootRoute implements ServerRoute {
     timeout: 504,
   };
 
-  readonly method = 'GET';
-  readonly path = '/';
-
   constructor(private kibanaConfig: KibanaConfig, private logger: Logger) {
     this.handler = this.handler.bind(this);
-
-    return pick(this, ['method', 'path', 'handler']) as RootRoute;
   }
 
   async handler(request: Request, toolkit: ResponseToolkit): Promise<ResponseObject> {
     const body = await this.poll();
-    const code = RootRoute.STATUS_CODE[body.status];
+    const code = StatusHandler.STATUS_CODE[body.status];
 
     this.logger.debug(`Returning ${code} response with body: ${JSON.stringify(body)}`);
 
     return toolkit.response(body).type('application/json').code(code);
   }
 
-  private async poll(): Promise<RootRouteResponse> {
+  private async poll(): Promise<StatusRouteResponse> {
     const hosts = await Promise.all(this.kibanaConfig.hosts.map(this.pollHost.bind(this)));
     const statuses = chain(hosts).map('status').uniq().value();
     const status = statuses.length <= 1 ? statuses[0] ?? 'healthy' : 'unhealthy';
@@ -81,7 +78,7 @@ export class RootRoute implements ServerRoute {
 
     try {
       const response = await this.fetch(host);
-      const status = RootRoute.isHealthy(response) ? 'healthy' : 'unhealthy';
+      const status = StatusHandler.isHealthy(response) ? 'healthy' : 'unhealthy';
       this.logger.debug(
         `${capitalize(status)} response from '${host}' with code ${response.status}`
       );
@@ -112,8 +109,9 @@ export class RootRoute implements ServerRoute {
     }
   }
 
-  private async fetch(url: string) {
+  private async fetch(host: string) {
-    const { protocol } = new URL(url);
+    const url = new URL(host);
+    appendStatusApiPath(url);
 
     const controller = new AbortController();
     const timeoutId = setTimeout(
@@ -123,7 +121,7 @@ export class RootRoute implements ServerRoute {
 
     try {
       return await nodeFetch(url, {
-        agent: protocol === 'https:' ? this.getAgent() : undefined,
+        agent: url.protocol === 'https:' ? this.getAgent() : undefined,
         signal: controller.signal,
         redirect: 'manual',
       });
@@ -161,3 +159,7 @@ export class RootRoute implements ServerRoute {
     return options;
   }
 }
+
+const appendStatusApiPath = (url: URL) => {
+  url.pathname = `${url.pathname}/${statusApiPath}`.replace(/\/{2,}/g, '/');
+};

packages/kbn-health-gateway-server/src/kibana/kibana_service.test.ts

@@ -50,6 +50,19 @@ describe('KibanaService', () => {
         expect.objectContaining({
           method: 'GET',
           path: '/',
+          handler: expect.any(Function),
+        })
+      );
+    });
+
+    test('registers /api/status route with the server', async () => {
+      const kibanaService = new KibanaService({ config, logger });
+      await kibanaService.start({ server });
+      expect(server.addRoute).toHaveBeenCalledWith(
+        expect.objectContaining({
+          method: 'GET',
+          path: '/api/status',
+          handler: expect.any(Function),
         })
       );
     });

packages/kbn-health-gateway-server/src/kibana/kibana_service.ts

@@ -10,7 +10,7 @@ import type { IConfigService } from '@kbn/config';
 import type { Logger, LoggerFactory } from '@kbn/logging';
 import { ServerStart } from '../server';
 import { KibanaConfig } from './kibana_config';
-import { RootRoute } from './routes';
+import { StatusHandler } from './handlers';
 
 interface KibanaServiceStartDependencies {
   server: ServerStart;
@@ -34,7 +34,17 @@ export class KibanaService {
   }
 
   async start({ server }: KibanaServiceStartDependencies) {
-    server.addRoute(new RootRoute(this.kibanaConfig, this.logger));
+    const statusHandler = new StatusHandler(this.kibanaConfig, this.logger);
+    server.addRoute({
+      method: 'GET',
+      path: '/',
+      handler: statusHandler.handler,
+    });
+    server.addRoute({
+      method: 'GET',
+      path: '/api/status',
+      handler: statusHandler.handler,
+    });
     this.logger.info('Server is ready');
   }
 

test/health_gateway/fixtures/flaky.yaml

@@ -4,8 +4,8 @@ server:
 
 kibana:
   hosts:
-    - ${KIBANA_URL}/api/status/ok
+    - ${KIBANA_URL}/health/ok
-    - ${KIBANA_URL}/api/status/flaky?session=${SESSION}
+    - ${KIBANA_URL}/health/flaky?session=${SESSION}
 
 logging:
   root:

test/health_gateway/fixtures/healthy.yaml

@@ -4,9 +4,9 @@ server:
 
 kibana:
   hosts:
-    - ${KIBANA_URL}/api/status/ok
+    - ${KIBANA_URL}/health/ok
-    - ${KIBANA_URL}/api/status/redirect
+    - ${KIBANA_URL}/health/redirect
-    - ${KIBANA_URL}/api/status/unauthorized
+    - ${KIBANA_URL}/health/unauthorized
 
 logging:
   root:

test/health_gateway/fixtures/invalid.yaml

@@ -4,7 +4,7 @@ server:
 
 kibana:
   hosts:
-    - http://localhost:65537/api/status/ok
+    - http://localhost:65537/health/ok
   requestTimeout: 2s
 
 logging:

test/health_gateway/fixtures/mixed.yaml

@@ -4,8 +4,8 @@ server:
 
 kibana:
   hosts:
-    - ${KIBANA_URL}/api/status/ok
+    - ${KIBANA_URL}/health/ok
-    - ${KIBANA_URL}/api/status/not-found
+    - ${KIBANA_URL}/health/not-found
 
 logging:
   root:

test/health_gateway/fixtures/timeout.yaml

@@ -4,7 +4,7 @@ server:
 
 kibana:
   hosts:
-    - ${KIBANA_URL}/api/status/slow
+    - ${KIBANA_URL}/health/slow
   requestTimeout: 2s
 
 logging:

test/health_gateway/fixtures/unhealthy.yaml

@@ -4,7 +4,7 @@ server:
 
 kibana:
   hosts:
-    - ${KIBANA_URL}/api/status/not-found
+    - ${KIBANA_URL}/health/not-found
 
 logging:
   root:

test/health_gateway/plugins/status/server/plugin.ts

@@ -13,23 +13,27 @@ export class HealthGatewayStatusPlugin implements Plugin<void, void> {
   public setup(core: CoreSetup) {
     const router = core.http.createRouter();
 
-    router.get({ path: '/api/status/ok', validate: {} }, async (context, req, res) => res.ok());
+    router.get({ path: '/health/ok/api/status', validate: {} }, async (context, req, res) =>
-
+      res.ok()
-    router.get({ path: '/api/status/redirect', validate: {} }, async (context, req, res) =>
-      res.redirected({ headers: { location: '/api/status/ok' } })
     );
 
-    router.get({ path: '/api/status/unauthorized', validate: {} }, async (context, req, res) =>
+    router.get({ path: '/health/redirect/api/status', validate: {} }, async (context, req, res) =>
+      res.redirected({ headers: { location: '/health/ok/api/status' } })
+    );
+
+    router.get(
+      { path: '/health/unauthorized/api/status', validate: {} },
+      async (context, req, res) =>
         res.unauthorized({
           headers: { 'www-authenticate': 'Basic' },
         })
     );
 
-    router.get({ path: '/api/status/not-found', validate: {} }, async (context, req, res) =>
+    router.get({ path: '/health/not-found/api/status', validate: {} }, async (context, req, res) =>
       res.notFound()
     );
 
-    router.get({ path: '/api/status/slow', validate: {} }, async (context, req, res) => {
+    router.get({ path: '/health/slow/api/status', validate: {} }, async (context, req, res) => {
       await new Promise((resolve) => setTimeout(resolve, 5000));
 
       return res.ok();
@@ -38,7 +42,7 @@ export class HealthGatewayStatusPlugin implements Plugin<void, void> {
     const sessions = new Set<string>();
     router.get(
       {
-        path: '/api/status/flaky',
+        path: '/health/flaky/api/status',
         validate: {
           query: schema.object({ session: schema.string() }),
         },
@@ -58,5 +62,6 @@ export class HealthGatewayStatusPlugin implements Plugin<void, void> {
   }
 
   public start() {}
+
   public stop() {}
 }

test/health_gateway/services/health_gateway.ts

@@ -66,9 +66,9 @@ export class HealthGatewayService extends FtrService {
     this.port = undefined;
   }
 
-  poll() {
+  poll(path: string) {
     this.assertRunning();
 
-    return supertest(`http://${this.host}:${this.port}`).get('/').send();
+    return supertest(`http://${this.host}:${this.port}`).get(path).send();
   }
 }

test/health_gateway/tests/index.ts

@@ -6,58 +6,10 @@
  * Side Public License, v 1.
  */
 
-import expect from '@kbn/expect';
 import { FtrProviderContext } from './ftr_provider_context';
 
-export default function ({ getService }: FtrProviderContext) {
+export default function ({ loadTestFile }: FtrProviderContext) {
-  const healthGateway = getService('healthGateway');
-
   describe('health gateway', () => {
-    it('returns 200 on healthy hosts', async () => {
+    loadTestFile(require.resolve('./status'));
-      await healthGateway.start('fixtures/healthy.yaml');
-
-      const { body } = await healthGateway.poll().expect(200);
-      expect(body).to.have.property('status', 'healthy');
-    });
-
-    it('returns 503 on unhealthy host', async () => {
-      await healthGateway.start('fixtures/unhealthy.yaml');
-
-      const { body } = await healthGateway.poll().expect(503);
-      expect(body).to.have.property('status', 'unhealthy');
-    });
-
-    it('returns 503 on mixed responses', async () => {
-      await healthGateway.start('fixtures/mixed.yaml');
-
-      const { body } = await healthGateway.poll().expect(503);
-      expect(body).to.have.property('status', 'unhealthy');
-    });
-
-    it('returns 504 on timeout', async () => {
-      await healthGateway.start('fixtures/timeout.yaml');
-
-      const { body } = await healthGateway.poll().expect(504);
-      expect(body).to.have.property('status', 'timeout');
-    });
-
-    it('returns 502 on exception', async () => {
-      await healthGateway.start('fixtures/invalid.yaml');
-
-      const { body } = await healthGateway.poll().expect(502);
-      expect(body).to.have.property('status', 'failure');
-    });
-
-    it('returns different status codes on state changes', async () => {
-      await healthGateway.start('fixtures/flaky.yaml', { env: { SESSION: `${Math.random()}` } });
-
-      await healthGateway.poll().expect(200);
-      await healthGateway.poll().expect(503);
-      await healthGateway.poll().expect(200);
-    });
-
-    afterEach(async () => {
-      await healthGateway.stop();
-    });
   });
 }

test/health_gateway/tests/status.ts

@@ -0,0 +1,69 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0 and the Server Side Public License, v 1; you may not use this file except
+ * in compliance with, at your election, the Elastic License 2.0 or the Server
+ * Side Public License, v 1.
+ */
+
+import expect from '@kbn/expect';
+import { FtrProviderContext } from './ftr_provider_context';
+
+export default function ({ getService }: FtrProviderContext) {
+  const healthGateway = getService('healthGateway');
+
+  describe('status API', () => {
+    afterEach(async () => {
+      await healthGateway.stop();
+    });
+
+    ['/', '/api/status'].forEach((path) => {
+      describe(`${path}`, () => {
+        it('returns 200 on healthy hosts', async () => {
+          await healthGateway.start('fixtures/healthy.yaml');
+
+          const { body } = await healthGateway.poll(path).expect(200);
+          expect(body).to.have.property('status', 'healthy');
+        });
+
+        it('returns 503 on unhealthy host', async () => {
+          await healthGateway.start('fixtures/unhealthy.yaml');
+
+          const { body } = await healthGateway.poll(path).expect(503);
+          expect(body).to.have.property('status', 'unhealthy');
+        });
+
+        it('returns 503 on mixed responses', async () => {
+          await healthGateway.start('fixtures/mixed.yaml');
+
+          const { body } = await healthGateway.poll(path).expect(503);
+          expect(body).to.have.property('status', 'unhealthy');
+        });
+
+        it('returns 504 on timeout', async () => {
+          await healthGateway.start('fixtures/timeout.yaml');
+
+          const { body } = await healthGateway.poll(path).expect(504);
+          expect(body).to.have.property('status', 'timeout');
+        });
+
+        it('returns 502 on exception', async () => {
+          await healthGateway.start('fixtures/invalid.yaml');
+
+          const { body } = await healthGateway.poll(path).expect(502);
+          expect(body).to.have.property('status', 'failure');
+        });
+
+        it('returns different status codes on state changes', async () => {
+          await healthGateway.start('fixtures/flaky.yaml', {
+            env: { SESSION: `${Math.random()}` },
+          });
+
+          await healthGateway.poll(path).expect(200);
+          await healthGateway.poll(path).expect(503);
+          await healthGateway.poll(path).expect(200);
+        });
+      });
+    });
+  });
+}