[Search service] Add support for ES request preference (elastic#49424)

* Add support for ES preference

* Fix name of test

src/plugins/data/public/search/es_search/es_search_strategy.ts

@@ -20,18 +20,25 @@
 import { Observable } from 'rxjs';
 import { ES_SEARCH_STRATEGY, IEsSearchResponse } from '../../../common/search';
 import { SYNC_SEARCH_STRATEGY } from '../sync_search_strategy';
+import { getEsPreference } from './get_es_preference';
 import { TSearchStrategyProvider, ISearchStrategy, ISearchGeneric, ISearchContext } from '..';
 
 export const esSearchStrategyProvider: TSearchStrategyProvider<typeof ES_SEARCH_STRATEGY> = (
   context: ISearchContext,
   search: ISearchGeneric
 ): ISearchStrategy<typeof ES_SEARCH_STRATEGY> => {
   return {
-    search: (request, options) =>
-      search(
+    search: (request, options) => {
+      if (typeof request.params.preference === 'undefined') {
+        const setPreference = context.core.uiSettings.get('courier:setRequestPreference');
+        const customPreference = context.core.uiSettings.get('courier:customRequestPreference');
+        request.params.preference = getEsPreference(setPreference, customPreference);
+      }
+      return search(
         { ...request, serverStrategy: ES_SEARCH_STRATEGY },
         options,
         SYNC_SEARCH_STRATEGY
-      ) as Observable<IEsSearchResponse>,
+      ) as Observable<IEsSearchResponse>;
+    },
   };
 };

src/plugins/data/public/search/es_search/get_es_preference.test.ts

@@ -0,0 +1,46 @@
+/*
+ * Licensed to Elasticsearch B.V. under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch B.V. licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import { getEsPreference } from './get_es_preference';
+
+jest.useFakeTimers();
+
+describe('Get ES preference', () => {
+  test('returns the session ID if set to sessionId', () => {
+    const setPreference = 'sessionId';
+    const customPreference = 'foobar';
+    const sessionId = 'my_session_id';
+    const preference = getEsPreference(setPreference, customPreference, sessionId);
+    expect(preference).toBe(sessionId);
+  });
+
+  test('returns the custom preference if set to custom', () => {
+    const setPreference = 'custom';
+    const customPreference = 'foobar';
+    const preference = getEsPreference(setPreference, customPreference);
+    expect(preference).toBe(customPreference);
+  });
+
+  test('returns undefined if set to none', () => {
+    const setPreference = 'none';
+    const customPreference = 'foobar';
+    const preference = getEsPreference(setPreference, customPreference);
+    expect(preference).toBe(undefined);
+  });
+});

src/plugins/data/public/search/es_search/get_es_preference.ts

@@ -0,0 +1,29 @@
+/*
+ * Licensed to Elasticsearch B.V. under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch B.V. licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+const defaultSessionId = `${Date.now()}`;
+
+export function getEsPreference(
+  setRequestPreference: string,
+  customRequestPreference?: string,
+  sessionId: string = defaultSessionId
+) {
+  if (setRequestPreference === 'sessionId') return `${sessionId}`;
+  return setRequestPreference === 'custom' ? customRequestPreference : undefined;
+}