chore: revamp transactional impl (#4916)

## About the changes
This transactional implementation decorates a service with a
transactional method that removes the need to start transactions in the
method using the service.

This is a gradual rollout with a feature toggle, just because
transactions are not easy.

src/lib/__snapshots__/create-config.test.ts.snap

@@ -105,6 +105,7 @@ exports[`should create default config 1`] = `
       "proPlanAutoCharge": false,
       "responseTimeWithAppNameKillSwitch": false,
       "strictSchemaValidation": false,
+      "transactionalDecorator": false,
       "variantTypeNumber": false,
     },
   },
@@ -144,6 +145,7 @@ exports[`should create default config 1`] = `
       "proPlanAutoCharge": false,
       "responseTimeWithAppNameKillSwitch": false,
       "strictSchemaValidation": false,
+      "transactionalDecorator": false,
       "variantTypeNumber": false,
     },
     "externalResolver": {

src/lib/db/transaction.ts

@@ -20,3 +20,34 @@ export const createKnexTransactionStarter = (
     }
     return transaction;
 };
+
+export type DbServiceFactory<S> = (db: Knex) => S;
+export type WithTransactional<S> = S & {
+    transactional: <R>(fn: (service: S) => R) => Promise<R>;
+};
+
+export function withTransactional<S>(
+    serviceFactory: (db: Knex) => S,
+    db: Knex,
+): WithTransactional<S> {
+    const service = serviceFactory(db) as WithTransactional<S>;
+
+    service.transactional = async <R>(fn: (service: S) => R) =>
+        db.transaction(async (trx: Knex.Transaction) => {
+            const transactionalService = serviceFactory(trx);
+            return fn(transactionalService);
+        });
+
+    return service;
+}
+
+/** Just for testing purposes */
+export function withFakeTransactional<S>(service: S): WithTransactional<S> {
+    const serviceWithFakeTransactional = service as WithTransactional<S>;
+
+    serviceWithFakeTransactional.transactional = async <R>(
+        fn: (service: S) => R,
+    ) => fn(serviceWithFakeTransactional);
+
+    return serviceWithFakeTransactional;
+}

src/lib/features/export-import-toggles/createExportImportService.ts

@@ -43,6 +43,7 @@ import {
     createFakePrivateProjectChecker,
     createPrivateProjectChecker,
 } from '../private-project/createPrivateProjectChecker';
+import { DbServiceFactory } from 'lib/db/transaction';
 
 export const createFakeExportImportTogglesService = (
     config: IUnleashConfig,
@@ -127,13 +128,17 @@ export const createFakeExportImportTogglesService = (
     return exportImportService;
 };
 
-export const createExportImportTogglesService = (
+export const deferredExportImportTogglesService = (
-    db: Db,
     config: IUnleashConfig,
-): ExportImportService => {
+): DbServiceFactory<ExportImportService> => {
+    return (db: Db) => {
         const { eventBus, getLogger, flagResolver } = config;
         const importTogglesStore = new ImportTogglesStore(db);
-    const featureToggleStore = new FeatureToggleStore(db, eventBus, getLogger);
+        const featureToggleStore = new FeatureToggleStore(
+            db,
+            eventBus,
+            getLogger,
+        );
         const tagStore = new TagStore(db, eventBus, getLogger);
         const tagTypeStore = new TagTypeStore(db, eventBus, getLogger);
         const segmentStore = new SegmentStore(
@@ -233,3 +238,11 @@ export const createExportImportTogglesService = (
 
         return exportImportService;
     };
+};
+export const createExportImportTogglesService = (
+    db: Db,
+    config: IUnleashConfig,
+): ExportImportService => {
+    const unboundService = deferredExportImportTogglesService(config);
+    return unboundService(db);
+};

src/lib/features/export-import-toggles/export-import-controller.ts

@@ -3,7 +3,11 @@ import Controller from '../../routes/controller';
 import { Logger } from '../../logger';
 import ExportImportService from './export-import-service';
 import { OpenApiService } from '../../services';
-import { TransactionCreator, UnleashTransaction } from '../../db/transaction';
+import {
+    TransactionCreator,
+    UnleashTransaction,
+    WithTransactional,
+} from '../../db/transaction';
 import {
     IUnleashConfig,
     IUnleashServices,
@@ -28,14 +32,19 @@ import ApiUser from '../../types/api-user';
 class ExportImportController extends Controller {
     private logger: Logger;
 
+    /** @deprecated gradually rolling out exportImportV2 */
     private exportImportService: ExportImportService;
 
+    /** @deprecated gradually rolling out exportImportV2 */
     private transactionalExportImportService: (
         db: UnleashTransaction,
     ) => ExportImportService;
 
+    private exportImportServiceV2: WithTransactional<ExportImportService>;
+
     private openApiService: OpenApiService;
 
+    /** @deprecated gradually rolling out exportImportV2 */
     private readonly startTransaction: TransactionCreator<UnleashTransaction>;
 
     constructor(
@@ -43,10 +52,12 @@ class ExportImportController extends Controller {
         {
             exportImportService,
             transactionalExportImportService,
+            exportImportServiceV2,
             openApiService,
         }: Pick<
             IUnleashServices,
             | 'exportImportService'
+            | 'exportImportServiceV2'
             | 'openApiService'
             | 'transactionalExportImportService'
         >,
@@ -57,6 +68,7 @@ class ExportImportController extends Controller {
         this.exportImportService = exportImportService;
         this.transactionalExportImportService =
             transactionalExportImportService;
+        this.exportImportServiceV2 = exportImportServiceV2;
         this.startTransaction = startTransaction;
         this.openApiService = openApiService;
         this.route({
@@ -128,7 +140,13 @@ class ExportImportController extends Controller {
         this.verifyExportImportEnabled();
         const query = req.body;
         const userName = extractUsername(req);
-        const data = await this.exportImportService.export(query, userName);
+
+        const useTransactionalDecorator = this.config.flagResolver.isEnabled(
+            'transactionalDecorator',
+        );
+        const data = useTransactionalDecorator
+            ? await this.exportImportServiceV2.export(query, userName)
+            : await this.exportImportService.export(query, userName);
 
         this.openApiService.respondWithValidation(
             200,
@@ -145,7 +163,15 @@ class ExportImportController extends Controller {
         this.verifyExportImportEnabled();
         const dto = req.body;
         const { user } = req;
-        const validation = await this.startTransaction(async (tx) =>
+
+        const useTransactionalDecorator = this.config.flagResolver.isEnabled(
+            'transactionalDecorator',
+        );
+        const validation = useTransactionalDecorator
+            ? await this.exportImportServiceV2.transactional((service) =>
+                  service.validate(dto, user),
+              )
+            : await this.startTransaction(async (tx) =>
                   this.transactionalExportImportService(tx).validate(dto, user),
               );
 
@@ -172,9 +198,19 @@ class ExportImportController extends Controller {
 
         const dto = req.body;
 
+        const useTransactionalDecorator = this.config.flagResolver.isEnabled(
+            'transactionalDecorator',
+        );
+
+        if (useTransactionalDecorator) {
+            await this.exportImportServiceV2.transactional((service) =>
+                service.import(dto, user),
+            );
+        } else {
             await this.startTransaction(async (tx) =>
                 this.transactionalExportImportService(tx).import(dto, user),
             );
+        }
 
         res.status(200).end();
     }

src/lib/services/index.ts

@@ -50,8 +50,10 @@ import { Knex } from 'knex';
 import {
     createExportImportTogglesService,
     createFakeExportImportTogglesService,
+    deferredExportImportTogglesService,
 } from '../features/export-import-toggles/createExportImportService';
 import { Db } from '../db/db';
+import { withFakeTransactional, withTransactional } from '../db/transaction';
 import {
     createChangeRequestAccessReadModel,
     createFakeChangeRequestAccessService,
@@ -274,10 +276,12 @@ export const createServices = (
         projectService,
     );
 
-    // TODO: this is a temporary seam to enable packaging by feature
     const exportImportService = db
         ? createExportImportTogglesService(db, config)
         : createFakeExportImportTogglesService(config);
+    const exportImportServiceV2 = db
+        ? withTransactional(deferredExportImportTogglesService(config), db)
+        : withFakeTransactional(createFakeExportImportTogglesService(config));
     const transactionalExportImportService = (txDb: Knex.Transaction) =>
         createExportImportTogglesService(txDb, config);
     const transactionalFeatureToggleService = (txDb: Knex.Transaction) =>
@@ -380,6 +384,7 @@ export const createServices = (
         maintenanceService,
         exportImportService,
         transactionalExportImportService,
+        exportImportServiceV2,
         schedulerService,
         configurationRevisionService,
         transactionalFeatureToggleService,

src/lib/types/experimental.ts

@@ -31,7 +31,8 @@ export type IFlagKey =
     | 'privateProjects'
     | 'dependentFeatures'
     | 'datadogJsonTemplate'
-    | 'disableMetrics';
+    | 'disableMetrics'
+    | 'transactionalDecorator';
 
 export type IFlags = Partial<{ [key in IFlagKey]: boolean | Variant }>;
 
@@ -147,6 +148,10 @@ const flags: IFlags = {
         process.env.UNLEASH_EXPERIMENTAL_DISABLE_METRICS,
         false,
     ),
+    transactionalDecorator: parseEnvVarBoolean(
+        process.env.UNLEASH_EXPERIMENTAL_TRANSACTIONAL_DECORATOR,
+        false,
+    ),
 };
 
 export const defaultExperimentalOptions: IExperimentalOptions = {

src/lib/types/services.ts

@@ -45,6 +45,7 @@ import ConfigurationRevisionService from '../features/feature-toggle/configurati
 import EventAnnouncerService from 'lib/services/event-announcer-service';
 import { IPrivateProjectChecker } from '../features/private-project/privateProjectCheckerType';
 import { DependentFeaturesService } from '../features/dependent-features/dependent-features-service';
+import { WithTransactional } from 'lib/db/transaction';
 
 export interface IUnleashServices {
     accessService: AccessService;
@@ -88,10 +89,13 @@ export interface IUnleashServices {
     instanceStatsService: InstanceStatsService;
     favoritesService: FavoritesService;
     maintenanceService: MaintenanceService;
+    /** @deprecated prefer exportImportServiceV2, we're doing a gradual rollout */
     exportImportService: ExportImportService;
+    exportImportServiceV2: WithTransactional<ExportImportService>;
     configurationRevisionService: ConfigurationRevisionService;
     schedulerService: SchedulerService;
     eventAnnouncerService: EventAnnouncerService;
+    /** @deprecated prefer exportImportServiceV2, we're doing a gradual rollout */
     transactionalExportImportService: (
         db: Knex.Transaction,
     ) => ExportImportService;

src/server-dev.ts

@@ -45,6 +45,7 @@ process.nextTick(async () => {
                         accessOverview: true,
                         datadogJsonTemplate: true,
                         dependentFeatures: true,
+                        transactionalDecorator: true,
                     },
                 },
                 authentication: {