advanced setting to control search request preference (#17271)

* advanced setting to control search request preference

* add header tests

* add sentince about caching to description

* change courier:setRequestPreference to list and add courier:customRequestPreference

* update setting text

src/core_plugins/kibana/ui_setting_defaults.js

@@ -115,6 +115,27 @@ export function getUiSettingDefaults() {
         'When set to true, filter(s) will be ignored for a visualization ' +
         'when the visualization\'s index does not contain the filtering field.'
     },
+    'courier:setRequestPreference': {
+      value: 'sessionId',
+      options: ['sessionId', 'custom', 'none'],
+      type: 'select',
+      description: 'Allows you to set which shards handle your search requests. ' +
+        '<ul>' +
+        '<li><strong>sessionId:</strong> restricts operations to execute all search requests on the same shards. ' +
+        'This has the benefit of reusing shard caches across requests. ' +
+        '<li><strong>custom:</strong> allows you to define a your own preference. ' +
+        'Use <strong>courier:customRequestPreference</strong> to customize your preference value. ' +
+        '<li><strong>none:</strong> means do not set a preference. ' +
+        'This might provide better performance because requests can be spread across all shard copies. ' +
+        'However, results might be inconsistent because different shards might be in different refresh states.' +
+        '</ul>'
+    },
+    'courier:customRequestPreference': {
+      value: '_local',
+      type: 'string',
+      description: '<a href="https://www.elastic.co/guide/en/elasticsearch/reference/current/search-request-preference.html" target="_blank" rel="noopener noreferrer">Request Preference</a> ' +
+        ' used when <strong>courier:setRequestPreference</strong> is set to "custom".'
+    },
     'fields:popularLimit': {
       value: 10,
       description: 'The top N most popular fields to show',

src/ui/public/courier/fetch/request/request_fetch_params_to_body.js

@@ -30,7 +30,8 @@ export function requestFetchParamsToBody(
   Promise,
   timeFilter,
   kbnIndex,
-  sessionId) {
+  sessionId,
+  config) {
   const indexToListMapping = {};
   const timeBounds = timeFilter.getActiveBounds();
   const promises = requestsFetchParams.map(function (fetchParams) {
@@ -68,15 +69,19 @@ export function requestFetchParamsToBody(
           index = indexList;
         }
 
-        return JSON.stringify({
+        const header = {
           index,
           type: fetchParams.type,
           search_type: fetchParams.search_type,
           ignore_unavailable: true,
-          preference: sessionId,
-        })
-        + '\n'
-        + toJson(body, JSON.stringify);
+        };
+        if (config.get('courier:setRequestPreference') === 'sessionId') {
+          header.preference = sessionId;
+        } else if (config.get('courier:setRequestPreference') === 'custom') {
+          header.preference = config.get('courier:customRequestPreference');
+        }
+
+        return `${JSON.stringify(header)}\n${toJson(body, JSON.stringify)}`;
       });
   });
 

src/ui/public/courier/fetch/request/request_fetch_params_to_body.test.js

@@ -1,6 +1,8 @@
 import { requestFetchParamsToBody } from './request_fetch_params_to_body';
 import _ from 'lodash';
 
+const DEFAULT_SESSION_ID = '1';
+
 function requestFetchParamsToBodyWithDefaults(paramOverrides) {
   const paramDefaults = {
     requestFetchParams: [],
@@ -9,7 +11,12 @@ function requestFetchParamsToBodyWithDefaults(paramOverrides) {
       getActiveBounds: () => undefined,
     },
     kbnIndex: '.kibana',
-    sessionId: '1',
+    sessionId: DEFAULT_SESSION_ID,
+    config: {
+      get: () => {
+        return 'sessionId';
+      }
+    }
   };
   const params = { ...paramDefaults, ...paramOverrides };
 
@@ -19,6 +26,7 @@ function requestFetchParamsToBodyWithDefaults(paramOverrides) {
     params.timeFilter,
     params.kbnIndex,
     params.sessionId,
+    params.config,
   );
 }
 
@@ -73,10 +81,68 @@ describe('when indexList is empty', () => {
     }
   ];
 
-  it('queries the kibana index (.kibana) with a must_not match_all boolean', () => {
+  test('queries the kibana index (.kibana) with a must_not match_all boolean', () => {
     return requestFetchParamsToBodyWithDefaults({ requestFetchParams }).then(value => {
       expect(_.includes(value, '"index":[".kibana"]')).toBe(true);
       expect(_.includes(value, emptyMustNotQuery)).toBe(true);
     });
   });
 });
+
+describe('headers', () => {
+
+  const requestFetchParams = [
+    {
+      index: ['logstash-123'],
+      type: 'blah',
+      search_type: 'blah2',
+      body: { foo: 'bar' }
+    }
+  ];
+
+  const getHeader = async (paramOverrides) => {
+    const request = await requestFetchParamsToBodyWithDefaults(paramOverrides);
+    const requestParts = request.split('\n');
+    if (requestParts.length < 2) {
+      throw new Error('fetch Body does not contain expected format header newline body.');
+    }
+    return JSON.parse(requestParts[0]);
+  };
+
+  describe('search request preference', async () => {
+    test('should be set to sessionId when courier:setRequestPreference is "sessionId"', async () => {
+      const config = {
+        get: () => {
+          return 'sessionId';
+        }
+      };
+      const header = await getHeader({ requestFetchParams, config });
+      expect(header.preference).toBe(DEFAULT_SESSION_ID);
+    });
+
+    test('should be set to custom string when courier:setRequestPreference is "custom"', async () => {
+      const CUSTOM_PREFERENCE = '_local';
+      const config = {
+        get: (key) => {
+          if (key === 'courier:setRequestPreference') {
+            return 'custom';
+          } else if (key === 'courier:customRequestPreference') {
+            return CUSTOM_PREFERENCE;
+          }
+        }
+      };
+      const header = await getHeader({ requestFetchParams, config });
+      expect(header.preference).toBe(CUSTOM_PREFERENCE);
+    });
+
+    test('should not be set when courier:setRequestPreference is "none"', async () => {
+      const config = {
+        get: () => {
+          return 'none';
+        }
+      };
+      const header = await getHeader({ requestFetchParams, config });
+      expect(header.preference).toBe(undefined);
+    });
+  });
+});

src/ui/public/courier/fetch/request/request_fetch_params_to_body_provider.js

@@ -1,12 +1,13 @@
 import { requestFetchParamsToBody } from './request_fetch_params_to_body';
 
-export function RequestFetchParamsToBodyProvider(Promise, timefilter, kbnIndex, sessionId) {
+export function RequestFetchParamsToBodyProvider(Promise, timefilter, kbnIndex, sessionId, config) {
   return (requestsFetchParams) => (
     requestFetchParamsToBody(
       requestsFetchParams,
       Promise,
       timefilter,
       kbnIndex,
-      sessionId)
+      sessionId,
+      config)
   );
 }