Review nits

src/core/server/elasticsearch/client/cluster_client.ts

@@ -19,7 +19,7 @@
 
 import { Client } from '@elastic/elasticsearch';
 import { Logger } from '../../logging';
-import { GetAuthHeaders, isRealRequest, Headers } from '../../http';
+import { GetAuthHeaders, Headers, isKibanaRequest, isRealRequest } from '../../http';
 import { ensureRawRequest, filterHeaders, KibanaRequest } from '../../http/router';
 import { ScopeableRequest } from '../types';
 import { ElasticsearchClient } from './types';
@@ -96,8 +96,7 @@ export class ClusterClient implements ICustomClusterClient {
     let scopedHeaders: Headers;
     if (isRealRequest(request)) {
       const requestHeaders = ensureRawRequest(request).headers;
-      const requestIdHeaders =
-        request instanceof KibanaRequest ? { 'x-opaque-id': request.id } : {};
+      const requestIdHeaders = isKibanaRequest(request) ? { 'x-opaque-id': request.id } : {};
       const authHeaders = this.getAuthHeaders(request);
 
       scopedHeaders = filterHeaders({ ...requestHeaders, ...requestIdHeaders, ...authHeaders }, [

src/core/server/elasticsearch/legacy/cluster_client.ts

@@ -20,7 +20,7 @@ import { Client } from 'elasticsearch';
 import { get } from 'lodash';
 
 import { LegacyElasticsearchErrorHelpers } from './errors';
-import { GetAuthHeaders, isRealRequest, KibanaRequest } from '../../http';
+import { GetAuthHeaders, KibanaRequest, isKibanaRequest, isRealRequest } from '../../http';
 import { AuditorFactory } from '../../audit_trail';
 import { filterHeaders, ensureRawRequest } from '../../http/router';
 import { Logger } from '../../logging';
@@ -218,8 +218,7 @@ export class LegacyClusterClient implements ILegacyClusterClient {
   private getScopedAuditor(request?: ScopeableRequest) {
     // TODO: support alternative credential owners from outside of Request context in #39430
     if (request && isRealRequest(request)) {
-      const kibanaRequest =
-        request instanceof KibanaRequest ? request : KibanaRequest.from(request);
+      const kibanaRequest = isKibanaRequest(request) ? request : KibanaRequest.from(request);
       const auditorFactory = this.getAuditorFactory();
       return auditorFactory.asScoped(kibanaRequest);
     }
@@ -259,9 +258,9 @@ export class LegacyClusterClient implements ILegacyClusterClient {
       return request && request.headers ? request.headers : {};
     }
     const authHeaders = this.getAuthHeaders(request);
-    const headers = ensureRawRequest(request).headers;
-    const requestIdHeaders = request instanceof KibanaRequest ? { 'x-opaque-id': request.id } : {};
+    const requestHeaders = ensureRawRequest(request).headers;
+    const requestIdHeaders = isKibanaRequest(request) ? { 'x-opaque-id': request.id } : {};
 
-    return { ...headers, ...authHeaders, ...requestIdHeaders };
+    return { ...requestHeaders, ...requestIdHeaders, ...authHeaders };
   }
 }

src/core/server/http/http_server.ts

@@ -313,6 +313,7 @@ export class HttpServer {
   private setupRequestStateAssignment(config: HttpConfig) {
     this.server!.ext('onRequest', (request, responseToolkit) => {
       request.app = {
+        ...(request.app ?? {}),
         requestId: getRequestId(request, config.requestId),
       } as KibanaRequestState;
       return responseToolkit.continue;

src/core/server/http/index.ts

@@ -24,6 +24,7 @@ export { AuthStatus, GetAuthState, IsAuthenticated } from './auth_state_storage'
 export {
   CustomHttpResponseOptions,
   IKibanaSocket,
+  isKibanaRequest,
   isRealRequest,
   Headers,
   HttpResponseOptions,

src/core/server/http/router/index.ts

@@ -26,6 +26,7 @@ export {
   KibanaRequestRouteOptions,
   KibanaRouteOptions,
   KibanaRequestState,
+  isKibanaRequest,
   isRealRequest,
   LegacyRequest,
   ensureRawRequest,

src/core/server/http/router/request.ts

@@ -299,7 +299,11 @@ export class KibanaRequest<
 export const ensureRawRequest = (request: KibanaRequest | LegacyRequest) =>
   isKibanaRequest(request) ? request[requestSymbol] : request;
 
-function isKibanaRequest(request: unknown): request is KibanaRequest {
+/**
+ * Checks if an incoming request is a {@link KibanaRequest}
+ * @internal
+ */
+export function isKibanaRequest(request: unknown): request is KibanaRequest {
   return request instanceof KibanaRequest;
 }