[Logs onboarding] elastic-agent.yml file now includes es host with ports (#162490)

Closes https://github.com/elastic/kibana/issues/162141.

### Changes
- Created an `esLegacyConfigService` to access esConfiguration and get
the hosts (protocol + url + port).
- Initialised the service mentioned using
`core.elasticsearch.legacy.config$`.
- Injected `esLegacyConfigService` as a resource for routes.
- Stop service whenever plugin is stopped.

x-pack/plugins/observability_onboarding/server/plugin.ts

@@ -24,6 +24,7 @@ import {
 } from './types';
 import { ObservabilityOnboardingConfig } from '.';
 import { observabilityOnboardingState } from './saved_objects/observability_onboarding_status';
+import { EsLegacyConfigService } from './services/es_legacy_config_service';
 
 export class ObservabilityOnboardingPlugin
   implements
@@ -35,6 +36,8 @@ export class ObservabilityOnboardingPlugin
     >
 {
   private readonly logger: Logger;
+  esLegacyConfigService = new EsLegacyConfigService();
+
   constructor(
     private readonly initContext: PluginInitializerContext<ObservabilityOnboardingConfig>
   ) {
@@ -47,6 +50,7 @@ export class ObservabilityOnboardingPlugin
     plugins: ObservabilityOnboardingPluginSetupDependencies
   ) {
     this.logger.debug('observability_onboarding: Setup');
+    this.esLegacyConfigService.setup(core.elasticsearch.legacy.config$);
 
     core.savedObjects.registerType(observabilityOnboardingState);
 
@@ -70,6 +74,9 @@ export class ObservabilityOnboardingPlugin
       repository: getObservabilityOnboardingServerRouteRepository(),
       plugins: resourcePlugins,
       config,
+      services: {
+        esLegacyConfigService: this.esLegacyConfigService,
+      },
     });
 
     return {};
@@ -81,5 +88,7 @@ export class ObservabilityOnboardingPlugin
     return {};
   }
 
-  public stop() {}
+  public stop() {
+    this.esLegacyConfigService.stop();
+  }
 }

x-pack/plugins/observability_onboarding/server/routes/custom_logs/get_fallback_urls.ts

@@ -5,31 +5,10 @@
  * 2.0.
  */
 
-import type { Client } from '@elastic/elasticsearch';
 import { CoreStart } from '@kbn/core/server';
+import { EsLegacyConfigService } from '../../services/es_legacy_config_service';
 
-export function getFallbackUrls(coreStart: CoreStart) {
-  const esClient = coreStart.elasticsearch.client.asInternalUser as Client;
-  const [elasticsearchUrl] = getElasticsearchUrl(esClient);
-  const kibanaUrl = getKibanaUrl(coreStart);
-  return { elasticsearchUrl, kibanaUrl };
-}
-
-function getElasticsearchUrl(esClient: Client): string[] {
-  const aliveConnections = esClient.connectionPool.connections.filter(
-    ({ status }) => status === 'alive'
-  );
-  if (aliveConnections.length) {
-    return aliveConnections.map(({ url }) => {
-      const { protocol, host } = new URL(url);
-      return `${protocol}//${host}`;
-    });
-  }
-
-  return ['http://localhost:9200'];
-}
-
-function getKibanaUrl({ http }: CoreStart) {
+export function getFallbackKibanaUrl({ http }: CoreStart) {
   const basePath = http.basePath;
   const { protocol, hostname, port } = http.getServerInfo();
   return `${protocol}://${hostname}:${port}${basePath
@@ -37,3 +16,11 @@ function getKibanaUrl({ http }: CoreStart) {
     .prepend('/')
     .slice(0, -1)}`;
 }
+
+export async function getFallbackESUrl(
+  esLegacyConfigService: EsLegacyConfigService
+) {
+  const config = await esLegacyConfigService.readConfig();
+
+  return config.hosts;
+}

x-pack/plugins/observability_onboarding/server/routes/custom_logs/route.ts

@@ -11,7 +11,7 @@ import { ObservabilityOnboardingState } from '../../saved_objects/observability_
 import { createObservabilityOnboardingServerRoute } from '../create_observability_onboarding_server_route';
 import { createShipperApiKey } from './api_key/create_shipper_api_key';
 import { hasLogMonitoringPrivileges } from './api_key/has_log_monitoring_privileges';
-import { getFallbackUrls } from './get_fallback_urls';
+import { getFallbackKibanaUrl } from './get_fallback_urls';
 import { getHasLogs } from './get_has_logs';
 import { getObservabilityOnboardingState } from './get_observability_onboarding_state';
 import { saveObservabilityOnboardingState } from './save_observability_onboarding_state';
@@ -52,7 +52,7 @@ const installShipperSetupRoute = createObservabilityOnboardingServerRoute({
     const kibanaUrl =
       core.setup.http.basePath.publicBaseUrl ?? // priority given to server.publicBaseUrl
       plugins.cloud?.setup?.kibanaUrl ?? // then cloud id
-      getFallbackUrls(coreStart).kibanaUrl; // falls back to local network binding
+      getFallbackKibanaUrl(coreStart); // falls back to local network binding
     const scriptDownloadUrl = `${kibanaUrl}/plugins/observabilityOnboarding/assets/standalone_agent_setup.sh`;
     const apiEndpoint = `${kibanaUrl}/internal/observability_onboarding`;
 

x-pack/plugins/observability_onboarding/server/routes/elastic_agent/route.ts

@@ -10,7 +10,7 @@ import { getAuthenticationAPIKey } from '../../lib/get_authentication_api_key';
 import { createObservabilityOnboardingServerRoute } from '../create_observability_onboarding_server_route';
 import { getObservabilityOnboardingState } from '../custom_logs/get_observability_onboarding_state';
 import { generateYml } from './generate_yml';
-import { getFallbackUrls } from '../custom_logs/get_fallback_urls';
+import { getFallbackESUrl } from '../custom_logs/get_fallback_urls';
 
 const generateConfig = createObservabilityOnboardingServerRoute({
   endpoint: 'GET /internal/observability_onboarding/elastic_agent/config',
@@ -26,6 +26,7 @@ const generateConfig = createObservabilityOnboardingServerRoute({
       core,
       plugins,
       request,
+      services: { esLegacyConfigService },
     } = resources;
     const authApiKey = getAuthenticationAPIKey(request);
 
@@ -33,9 +34,9 @@ const generateConfig = createObservabilityOnboardingServerRoute({
     const savedObjectsClient =
       coreStart.savedObjects.createInternalRepository();
 
-    const elasticsearchUrl =
-      plugins.cloud?.setup?.elasticsearchUrl ??
-      getFallbackUrls(coreStart).elasticsearchUrl;
+    const elasticsearchUrl = plugins.cloud?.setup?.elasticsearchUrl
+      ? [plugins.cloud?.setup?.elasticsearchUrl]
+      : await getFallbackESUrl(esLegacyConfigService);
 
     const savedState = await getObservabilityOnboardingState({
       savedObjectsClient,
@@ -50,7 +51,7 @@ const generateConfig = createObservabilityOnboardingServerRoute({
       apiKey: authApiKey
         ? `${authApiKey?.apiKeyId}:${authApiKey?.apiKey}`
         : '$API_KEY',
-      esHost: [elasticsearchUrl],
+      esHost: elasticsearchUrl,
       logfileId: `custom-logs-${Date.now()}`,
       serviceName: savedState?.state.serviceName,
     });

x-pack/plugins/observability_onboarding/server/routes/register_routes.ts

@@ -15,6 +15,7 @@ import {
 } from '@kbn/server-route-repository';
 import * as t from 'io-ts';
 import { ObservabilityOnboardingConfig } from '..';
+import { EsLegacyConfigService } from '../services/es_legacy_config_service';
 import { ObservabilityOnboardingRequestHandlerContext } from '../types';
 import { ObservabilityOnboardingRouteHandlerResources } from './types';
 
@@ -24,6 +25,9 @@ interface RegisterRoutes {
   logger: Logger;
   plugins: ObservabilityOnboardingRouteHandlerResources['plugins'];
   config: ObservabilityOnboardingConfig;
+  services: {
+    esLegacyConfigService: EsLegacyConfigService;
+  };
 }
 
 export function registerRoutes({
@@ -32,6 +36,7 @@ export function registerRoutes({
   logger,
   plugins,
   config,
+  services,
 }: RegisterRoutes) {
   const routes = Object.values(repository);
 
@@ -77,6 +82,7 @@ export function registerRoutes({
               },
             },
             config,
+            services,
           })) as any;
 
           if (data === undefined) {

x-pack/plugins/observability_onboarding/server/routes/types.ts

@@ -7,6 +7,7 @@
 import { CoreSetup, CoreStart, KibanaRequest, Logger } from '@kbn/core/server';
 import { ObservabilityOnboardingServerRouteRepository } from '.';
 import { ObservabilityOnboardingConfig } from '..';
+import { EsLegacyConfigService } from '../services/es_legacy_config_service';
 import {
   ObservabilityOnboardingPluginSetupDependencies,
   ObservabilityOnboardingPluginStartDependencies,
@@ -32,6 +33,9 @@ export interface ObservabilityOnboardingRouteHandlerResources {
     start: () => Promise<CoreStart>;
   };
   config: ObservabilityOnboardingConfig;
+  services: {
+    esLegacyConfigService: EsLegacyConfigService;
+  };
 }
 
 export interface ObservabilityOnboardingRouteCreateOptions {

x-pack/plugins/observability_onboarding/server/services/es_legacy_config_service.ts

@@ -0,0 +1,53 @@
+/*
+ * 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; you may not use this file except in compliance with the Elastic License
+ * 2.0.
+ */
+
+import { firstValueFrom, Observable, Subscription } from 'rxjs';
+import { ElasticsearchConfig } from '@kbn/core/server';
+
+export class EsLegacyConfigService {
+  /**
+   * The elasticsearch config value at a given point in time.
+   */
+  private config?: ElasticsearchConfig;
+
+  /**
+   * An observable that emits elasticsearch config.
+   */
+  private config$?: Observable<ElasticsearchConfig>;
+
+  /**
+   * A reference to the subscription to the elasticsearch observable
+   */
+  private configSub?: Subscription;
+
+  setup(config$: Observable<ElasticsearchConfig>) {
+    this.config$ = config$;
+    this.configSub = this.config$.subscribe((config) => {
+      this.config = config;
+    });
+  }
+
+  stop() {
+    if (this.configSub) {
+      this.configSub.unsubscribe();
+    }
+  }
+
+  async readConfig(): Promise<ElasticsearchConfig> {
+    if (!this.config$) {
+      throw new Error(
+        'Could not read elasticsearch config, this service has not been setup!'
+      );
+    }
+
+    if (!this.config) {
+      return firstValueFrom(this.config$);
+    }
+
+    return this.config;
+  }
+}