make isInlineScriptingEnabled resilient to ES errors (#170208)

## Summary

Fix https://github.com/elastic/kibana/issues/163787

Change the way `isInlineScriptingEnabled` function to retry retryable
errors from ES (similar to how the valid connection or migration ES
calls do)

packages/core/elasticsearch/core-elasticsearch-server-internal/index.ts

@@ -30,4 +30,5 @@ export { CoreElasticsearchRouteHandlerContext } from './src/elasticsearch_route_
 export { retryCallCluster, migrationRetryCallCluster } from './src/retry_call_cluster';
 export { isInlineScriptingEnabled } from './src/is_scripting_enabled';
 export { getCapabilitiesFromClient } from './src/get_capabilities';
+export { isRetryableEsClientError } from './src/retryable_es_client_errors';
 export type { ClusterInfo } from './src/get_cluster_info';

packages/core/elasticsearch/core-elasticsearch-server-internal/src/is_scripting_enabled.test.mocks.ts

@@ -0,0 +1,15 @@
+/*
+ * 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 and the Server Side Public License, v 1; you may not use this file except
+ * in compliance with, at your election, the Elastic License 2.0 or the Server
+ * Side Public License, v 1.
+ */
+
+export const isRetryableEsClientErrorMock = jest.fn();
+
+jest.doMock('./retryable_es_client_errors', () => {
+  return {
+    isRetryableEsClientError: isRetryableEsClientErrorMock,
+  };
+});

packages/core/elasticsearch/core-elasticsearch-server-internal/src/is_scripting_enabled.test.ts

@@ -6,6 +6,7 @@
  * Side Public License, v 1.
  */
 
+import { isRetryableEsClientErrorMock } from './is_scripting_enabled.test.mocks';
 import * as estypes from '@elastic/elasticsearch/lib/api/typesWithBodyKey';
 import { elasticsearchClientMock } from '@kbn/core-elasticsearch-client-server-mocks';
 import { isInlineScriptingEnabled } from './is_scripting_enabled';
@@ -94,4 +95,58 @@ describe('isInlineScriptingEnabled', () => {
 
     expect(await isInlineScriptingEnabled({ client })).toEqual(false);
   });
+
+  describe('resiliency', () => {
+    beforeEach(() => {
+      isRetryableEsClientErrorMock.mockReset();
+    });
+
+    const mockSuccessOnce = () => {
+      client.cluster.getSettings.mockResolvedValueOnce({
+        transient: {},
+        persistent: {},
+        defaults: {},
+      });
+    };
+    const mockErrorOnce = () => {
+      client.cluster.getSettings.mockResponseImplementationOnce(() => {
+        throw Error('ERR CON REFUSED');
+      });
+    };
+
+    it('retries the ES api call in case of retryable error', async () => {
+      isRetryableEsClientErrorMock.mockReturnValue(true);
+
+      mockErrorOnce();
+      mockSuccessOnce();
+
+      await expect(isInlineScriptingEnabled({ client, maxRetryDelay: 1 })).resolves.toEqual(true);
+      expect(client.cluster.getSettings).toHaveBeenCalledTimes(2);
+    });
+
+    it('throws in case of non-retryable error', async () => {
+      isRetryableEsClientErrorMock.mockReturnValue(false);
+
+      mockErrorOnce();
+      mockSuccessOnce();
+
+      await expect(isInlineScriptingEnabled({ client, maxRetryDelay: 0.1 })).rejects.toThrowError(
+        'ERR CON REFUSED'
+      );
+    });
+
+    it('retries up to `maxRetries` times', async () => {
+      isRetryableEsClientErrorMock.mockReturnValue(true);
+
+      mockErrorOnce();
+      mockErrorOnce();
+      mockErrorOnce();
+      mockSuccessOnce();
+
+      await expect(
+        isInlineScriptingEnabled({ client, maxRetryDelay: 0.1, maxRetries: 2 })
+      ).rejects.toThrowError('ERR CON REFUSED');
+      expect(client.cluster.getSettings).toHaveBeenCalledTimes(3);
+    });
+  });
 });

packages/core/elasticsearch/core-elasticsearch-server-internal/src/is_scripting_enabled.ts

@@ -6,27 +6,48 @@
  * Side Public License, v 1.
  */
 
+import { defer, map, retry, timer, firstValueFrom, throwError } from 'rxjs';
 import type { ElasticsearchClient } from '@kbn/core-elasticsearch-server';
+import { isRetryableEsClientError } from './retryable_es_client_errors';
 
 const scriptAllowedTypesKey = 'script.allowed_types';
 
 export const isInlineScriptingEnabled = async ({
   client,
+  maxRetries = 20,
+  maxRetryDelay = 64,
 }: {
   client: ElasticsearchClient;
+  maxRetries?: number;
+  maxRetryDelay?: number;
 }): Promise<boolean> => {
-  const settings = await client.cluster.getSettings({
-    include_defaults: true,
-    flat_settings: true,
-  });
+  return firstValueFrom(
+    defer(() => {
+      return client.cluster.getSettings({
+        include_defaults: true,
+        flat_settings: true,
+      });
+    }).pipe(
+      retry({
+        count: maxRetries,
+        delay: (error, retryIndex) => {
+          if (isRetryableEsClientError(error)) {
+            const retryDelay = 1000 * Math.min(Math.pow(2, retryIndex), maxRetryDelay); // 2s, 4s, 8s, 16s, 32s, 64s, 64s, 64s ...
+            return timer(retryDelay);
+          } else {
+            return throwError(error);
+          }
+        },
+      }),
+      map((settings) => {
+        const scriptAllowedTypes: string[] =
+          settings.transient[scriptAllowedTypesKey] ??
+          settings.persistent[scriptAllowedTypesKey] ??
+          settings.defaults![scriptAllowedTypesKey] ??
+          [];
 
-  // priority: transient -> persistent -> default
-  const scriptAllowedTypes: string[] =
-    settings.transient[scriptAllowedTypesKey] ??
-    settings.persistent[scriptAllowedTypesKey] ??
-    settings.defaults![scriptAllowedTypesKey] ??
-    [];
-
-  // when unspecified, the setting as a default `[]` value that means that both scriptings are allowed.
-  return scriptAllowedTypes.length === 0 || scriptAllowedTypes.includes('inline');
+        return scriptAllowedTypes.length === 0 || scriptAllowedTypes.includes('inline');
+      })
+    )
+  );
 };

packages/core/elasticsearch/core-elasticsearch-server-internal/src/retryable_es_client_errors.test.ts

@@ -0,0 +1,73 @@
+/*
+ * 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 and the Server Side Public License, v 1; you may not use this file except
+ * in compliance with, at your election, the Elastic License 2.0 or the Server
+ * Side Public License, v 1.
+ */
+
+import { errors as esErrors } from '@elastic/elasticsearch';
+import { elasticsearchClientMock } from '@kbn/core-elasticsearch-client-server-mocks';
+import { isRetryableEsClientError } from './retryable_es_client_errors';
+
+describe('isRetryableEsClientError', () => {
+  describe('returns `false` for', () => {
+    test('non-retryable response errors', async () => {
+      const error = new esErrors.ResponseError(
+        elasticsearchClientMock.createApiResponse({
+          body: { error: { type: 'cluster_block_exception' } },
+          statusCode: 400,
+        })
+      );
+
+      expect(isRetryableEsClientError(error)).toEqual(false);
+    });
+  });
+
+  describe('returns `true` for', () => {
+    it('NoLivingConnectionsError', () => {
+      const error = new esErrors.NoLivingConnectionsError(
+        'reason',
+        elasticsearchClientMock.createApiResponse()
+      );
+
+      expect(isRetryableEsClientError(error)).toEqual(true);
+    });
+
+    it('ConnectionError', () => {
+      const error = new esErrors.ConnectionError(
+        'reason',
+        elasticsearchClientMock.createApiResponse()
+      );
+      expect(isRetryableEsClientError(error)).toEqual(true);
+    });
+
+    it('TimeoutError', () => {
+      const error = new esErrors.TimeoutError(
+        'reason',
+        elasticsearchClientMock.createApiResponse()
+      );
+      expect(isRetryableEsClientError(error)).toEqual(true);
+    });
+
+    it('ResponseError of type snapshot_in_progress_exception', () => {
+      const error = new esErrors.ResponseError(
+        elasticsearchClientMock.createApiResponse({
+          body: { error: { type: 'snapshot_in_progress_exception' } },
+        })
+      );
+      expect(isRetryableEsClientError(error)).toEqual(true);
+    });
+
+    it.each([503, 401, 403, 408, 410, 429])('ResponseError with %p status code', (statusCode) => {
+      const error = new esErrors.ResponseError(
+        elasticsearchClientMock.createApiResponse({
+          statusCode,
+          body: { error: { type: 'reason' } },
+        })
+      );
+
+      expect(isRetryableEsClientError(error)).toEqual(true);
+    });
+  });
+});

packages/core/elasticsearch/core-elasticsearch-server-internal/src/retryable_es_client_errors.ts

@@ -0,0 +1,40 @@
+/*
+ * 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 and the Server Side Public License, v 1; you may not use this file except
+ * in compliance with, at your election, the Elastic License 2.0 or the Server
+ * Side Public License, v 1.
+ */
+
+import { errors as EsErrors } from '@elastic/elasticsearch';
+
+const retryResponseStatuses = [
+  503, // ServiceUnavailable
+  401, // AuthorizationException
+  403, // AuthenticationException
+  408, // RequestTimeout
+  410, // Gone
+  429, // TooManyRequests -> ES circuit breaker
+];
+
+/**
+ * Returns true if the given elasticsearch error should be retried
+ * by retry-based resiliency systems such as the SO migration, false otherwise.
+ */
+export const isRetryableEsClientError = (e: EsErrors.ElasticsearchClientError): boolean => {
+  if (
+    e instanceof EsErrors.NoLivingConnectionsError ||
+    e instanceof EsErrors.ConnectionError ||
+    e instanceof EsErrors.TimeoutError ||
+    (e instanceof EsErrors.ResponseError &&
+      (retryResponseStatuses.includes(e?.statusCode!) ||
+        // ES returns a 400 Bad Request when trying to close or delete an
+        // index while snapshots are in progress. This should have been a 503
+        // so once https://github.com/elastic/elasticsearch/issues/65883 is
+        // fixed we can remove this.
+        e?.body?.error?.type === 'snapshot_in_progress_exception'))
+  ) {
+    return true;
+  }
+  return false;
+};

packages/core/saved-objects/core-saved-objects-migration-server-internal/src/actions/catch_retryable_es_client_errors.ts

@@ -8,15 +8,7 @@
 
 import * as Either from 'fp-ts/lib/Either';
 import { errors as EsErrors } from '@elastic/elasticsearch';
-
-const retryResponseStatuses = [
-  503, // ServiceUnavailable
-  401, // AuthorizationException
-  403, // AuthenticationException
-  408, // RequestTimeout
-  410, // Gone
-  429, // TooManyRequests -> ES circuit breaker
-];
+import { isRetryableEsClientError } from '@kbn/core-elasticsearch-server-internal';
 
 export interface RetryableEsClientError {
   type: 'retryable_es_client_error';
@@ -27,18 +19,7 @@ export interface RetryableEsClientError {
 export const catchRetryableEsClientErrors = (
   e: EsErrors.ElasticsearchClientError
 ): Either.Either<RetryableEsClientError, never> => {
-  if (
-    e instanceof EsErrors.NoLivingConnectionsError ||
-    e instanceof EsErrors.ConnectionError ||
-    e instanceof EsErrors.TimeoutError ||
-    (e instanceof EsErrors.ResponseError &&
-      (retryResponseStatuses.includes(e?.statusCode!) ||
-        // ES returns a 400 Bad Request when trying to close or delete an
-        // index while snapshots are in progress. This should have been a 503
-        // so once https://github.com/elastic/elasticsearch/issues/65883 is
-        // fixed we can remove this.
-        e?.body?.error?.type === 'snapshot_in_progress_exception'))
-  ) {
+  if (isRetryableEsClientError(e)) {
     return Either.left({
       type: 'retryable_es_client_error' as const,
       message: e?.message,