[Reporting] Add max concurrent shards setting to schema (#170344)

## Summary

Closes https://github.com/elastic/kibana/issues/161561
This PR exposes the `max_concurrent_shards` setting in the schema for
customers for point in time CSV report generation.

### Checklist

- [x] [Unit or functional
tests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)
were updated or added to match the most common scenarios

---------

Co-authored-by: Tim Sullivan <tsullivan@users.noreply.github.com>

packages/kbn-generate-csv/src/generate_csv.test.ts

@@ -118,6 +118,7 @@ describe('CsvGenerator', () => {
       useByteOrderMarkEncoding: false,
       scroll: { size: 500, duration: '30s' },
       enablePanelActionDownload: true,
+      maxConcurrentShardRequests: 5,
     };
 
     searchSourceMock.getField = jest.fn((key: string) => {
@@ -245,6 +246,7 @@ describe('CsvGenerator', () => {
       useByteOrderMarkEncoding: false,
       scroll: { size: 500, duration: '30s' },
       enablePanelActionDownload: true,
+      maxConcurrentShardRequests: 5,
     };
 
     mockDataClient.search = jest.fn().mockImplementation(() =>
@@ -345,7 +347,7 @@ describe('CsvGenerator', () => {
 
     expect(mockDataClient.search).toHaveBeenCalledTimes(10);
     expect(mockDataClient.search).toBeCalledWith(
-      { params: { body: {}, ignore_throttled: undefined } },
+      { params: { body: {}, ignore_throttled: undefined, max_concurrent_shard_requests: 5 } },
       { strategy: 'es', transport: { maxRetries: 0, requestTimeout: '30s' } }
     );
 
@@ -356,7 +358,7 @@ describe('CsvGenerator', () => {
         index: 'logstash-*',
         keep_alive: '30s',
       },
-      { maxRetries: 0, requestTimeout: '30s' }
+      { maxConcurrentShardRequests: 5, maxRetries: 0, requestTimeout: '30s' }
     );
 
     expect(mockEsClient.asCurrentUser.closePointInTime).toHaveBeenCalledTimes(1);
@@ -763,6 +765,7 @@ describe('CsvGenerator', () => {
         useByteOrderMarkEncoding: false,
         scroll: { size: 500, duration: '30s' },
         enablePanelActionDownload: true,
+        maxConcurrentShardRequests: 5,
       };
       mockDataClient.search = jest.fn().mockImplementation(() =>
         Rx.of({
@@ -833,7 +836,7 @@ describe('CsvGenerator', () => {
         index: 'logstash-*',
         keep_alive: '30s',
       },
-      { maxRetries: 0, requestTimeout: '30s' }
+      { maxConcurrentShardRequests: 5, maxRetries: 0, requestTimeout: '30s' }
     );
 
     expect(mockEsClient.asCurrentUser.openPointInTime).toHaveBeenCalledWith(
@@ -843,13 +846,14 @@ describe('CsvGenerator', () => {
         index: 'logstash-*',
         keep_alive: '30s',
       },
-      { maxRetries: 0, requestTimeout: '30s' }
+      { maxConcurrentShardRequests: 5, maxRetries: 0, requestTimeout: '30s' }
     );
 
     expect(mockDataClient.search).toBeCalledWith(
       {
         params: {
           body: {},
+          max_concurrent_shard_requests: 5,
         },
       },
       { strategy: 'es', transport: { maxRetries: 0, requestTimeout: '30s' } }

packages/kbn-generate-csv/src/generate_csv.ts

@@ -12,6 +12,7 @@ import type { Writable } from 'stream';
 import { errors as esErrors, estypes } from '@elastic/elasticsearch';
 import type { IScopedClusterClient, IUiSettingsClient, Logger } from '@kbn/core/server';
 import type {
+  IEsSearchRequest,
   IKibanaSearchResponse,
   ISearchSource,
   ISearchStartSearchSource,
@@ -66,7 +67,11 @@ export class CsvGenerator {
   ) {}
 
   private async openPointInTime(indexPatternTitle: string, settings: CsvExportSettings) {
-    const { duration } = settings.scroll;
+    const {
+      includeFrozen,
+      maxConcurrentShardRequests,
+      scroll: { duration },
+    } = settings;
     let pitId: string | undefined;
     this.logger.debug(`Requesting PIT for: [${indexPatternTitle}]...`);
     try {
@@ -77,11 +82,12 @@ export class CsvGenerator {
           keep_alive: duration,
           ignore_unavailable: true,
           // @ts-expect-error ignore_throttled is not in the type definition, but it is accepted by es
-          ignore_throttled: settings.includeFrozen ? false : undefined, // "true" will cause deprecation warnings logged in ES
+          ignore_throttled: includeFrozen ? false : undefined, // "true" will cause deprecation warnings logged in ES
         },
         {
           requestTimeout: duration,
           maxRetries: 0,
+          maxConcurrentShardRequests,
         }
       );
       pitId = response.id;
@@ -135,7 +141,7 @@ export class CsvGenerator {
     settings: CsvExportSettings,
     searchAfter?: estypes.SortResults
   ) {
-    const { scroll: scrollSettings } = settings;
+    const { scroll: scrollSettings, maxConcurrentShardRequests } = settings;
     searchSource.setField('size', scrollSettings.size);
 
     if (searchAfter) {
@@ -153,8 +159,14 @@ export class CsvGenerator {
       throw new Error('Could not retrieve the search body!');
     }
 
-    const searchParams = { params: { body: searchBody } };
-    let results: estypes.SearchResponse<unknown>;
+    const searchParams: IEsSearchRequest = {
+      params: {
+        body: searchBody,
+        max_concurrent_shard_requests: maxConcurrentShardRequests,
+      },
+    };
+
+    let results: estypes.SearchResponse<unknown> | undefined;
     try {
       const { rawResponse, ...rawDetails } = await lastValueFrom(
         this.clients.data.search(searchParams, {

packages/kbn-generate-csv/src/get_export_settings.test.ts

@@ -30,6 +30,7 @@ describe('getExportSettings', () => {
     maxSizeBytes: 180000,
     scroll: { size: 500, duration: '30s' },
     useByteOrderMarkEncoding: false,
+    maxConcurrentShardRequests: 5,
     enablePanelActionDownload: true,
   };
   const logger = loggingSystemMock.createLogger();
@@ -62,6 +63,7 @@ describe('getExportSettings', () => {
         "escapeFormulaValues": false,
         "escapeValue": [Function],
         "includeFrozen": false,
+        "maxConcurrentShardRequests": 5,
         "maxSizeBytes": 180000,
         "scroll": Object {
           "duration": "30s",

packages/kbn-generate-csv/src/get_export_settings.ts

@@ -31,6 +31,7 @@ export interface CsvExportSettings {
   escapeFormulaValues: boolean;
   escapeValue: (value: string) => string;
   includeFrozen: boolean;
+  maxConcurrentShardRequests: number;
 }
 
 export const getExportSettings = async (
@@ -82,5 +83,6 @@ export const getExportSettings = async (
     checkForFormulas: config.checkForFormulas,
     escapeFormulaValues,
     escapeValue,
+    maxConcurrentShardRequests: config.maxConcurrentShardRequests,
   };
 };

packages/kbn-reporting/server/__snapshots__/config_schema.test.ts.snap

@@ -9,6 +9,7 @@ Object {
     "checkForFormulas": true,
     "enablePanelActionDownload": true,
     "escapeFormulaValues": false,
+    "maxConcurrentShardRequests": 5,
     "maxSizeBytes": ByteSizeValue {
       "valueInBytes": 262144000,
     },
@@ -70,6 +71,7 @@ Object {
     "checkForFormulas": true,
     "enablePanelActionDownload": true,
     "escapeFormulaValues": false,
+    "maxConcurrentShardRequests": 5,
     "maxSizeBytes": ByteSizeValue {
       "valueInBytes": 262144000,
     },

packages/kbn-reporting/server/config_schema.ts

@@ -75,6 +75,7 @@ const CsvSchema = schema.object({
     }),
     size: schema.number({ defaultValue: 500 }),
   }),
+  maxConcurrentShardRequests: schema.number({ defaultValue: 5 }),
 });
 
 const EncryptionKeySchema = schema.conditional(