feat(core): allow using AsyncLocalStorage for request context

Closes #575

docs/docs/async-local-storage.md

@@ -0,0 +1,19 @@
+---
+title: Using `AsyncLocalStorage`
+---
+
+By default, `domain` api use used in the `RequestContext` helper. Since v4.0.3,
+you can use the new `AsyncLocalStorage` too, if you are on up to date node version:
+
+```typescript
+const storage = new AsyncLocalStorage<EntityManager>();
+
+const orm = await MikroORM.init({
+  context: () => storage.getStore(),
+  // ...
+});
+
+app.use((req, res, next) => {
+  storage.run(orm.em.fork(true, true), next);
+});
+```

docs/sidebars.js

@@ -59,6 +59,7 @@ module.exports = {
       'entity-constructors',
       'multiple-schemas',
       'using-bigint-pks',
+      'async-local-storage',
       'custom-driver',
     ],
     'Example Integrations': [

docs/versioned_docs/version-4.0/async-local-storage.md

@@ -0,0 +1,19 @@
+---
+title: Using `AsyncLocalStorage`
+---
+
+By default, `domain` api use used in the `RequestContext` helper. Since v4.0.3,
+you can use the new `AsyncLocalStorage` too, if you are on up to date node version:
+
+```typescript
+const storage = new AsyncLocalStorage<EntityManager>();
+
+const orm = await MikroORM.init({
+  context: () => storage.getStore(),
+  // ...
+});
+
+app.use((req, res, next) => {
+  storage.run(orm.em.fork(true, true), next);
+});
+```

docs/versioned_sidebars/version-4.0-sidebars.json

@@ -232,6 +232,10 @@
           "type": "doc",
           "id": "version-4.0/using-bigint-pks"
         },
+        {
+          "type": "doc",
+          "id": "version-4.0/async-local-storage"
+        },
         {
           "type": "doc",
           "id": "version-4.0/custom-driver"

packages/core/package.json

@@ -54,8 +54,7 @@
     "fs-extra": "^9.0.1",
     "globby": "^11.0.1",
     "reflect-metadata": "^0.1.13",
-    "strip-json-comments": "^3.1.1",
-    "uuid": "^8.3.0"
+    "strip-json-comments": "^3.1.1"
   },
   "peerDependencies": {
     "@mikro-orm/entity-generator": "^4.0.0",

packages/core/src/EntityManager.ts

@@ -1,7 +1,6 @@
-import { v4 as uuid } from 'uuid';
 import { inspect } from 'util';
 
-import { Configuration, QueryHelper, RequestContext, Utils } from './utils';
+import { Configuration, QueryHelper, Utils } from './utils';
 import { AssignOptions, EntityAssigner, EntityFactory, EntityLoader, EntityRepository, EntityValidator, IdentifiedReference, Reference } from './entity';
 import { UnitOfWork } from './unit-of-work';
 import { CountOptions, DeleteOptions, EntityManagerType, FindOneOptions, FindOneOrFailOptions, FindOptions, IDatabaseDriver, UpdateOptions } from './drivers';
@@ -19,7 +18,8 @@ import { OptimisticLockError, ValidationError } from './errors';
  */
 export class EntityManager<D extends IDatabaseDriver = IDatabaseDriver> {
 
-  readonly id = uuid();
+  private static counter = 1;
+  readonly id = EntityManager.counter++;
   private readonly validator = new EntityValidator(this.config.get('strict'));
   private readonly repositoryMap: Dictionary<EntityRepository<AnyEntity>> = {};
   private readonly entityLoader: EntityLoader = new EntityLoader(this);
@@ -647,15 +647,15 @@ export class EntityManager<D extends IDatabaseDriver = IDatabaseDriver> {
    * Gets the UnitOfWork used by the EntityManager to coordinate operations.
    */
   getUnitOfWork(): UnitOfWork {
-    const em = this.useContext ? (RequestContext.getEntityManager() || this) : this;
+    const em = this.useContext ? (this.config.get('context')() || this) : this;
     return em.unitOfWork;
   }
 
   /**
    * Gets the EntityFactory used by the EntityManager.
    */
   getEntityFactory(): EntityFactory {
-    const em = this.useContext ? (RequestContext.getEntityManager() || this) : this;
+    const em = this.useContext ? (this.config.get('context')() || this) : this;
     return em.entityFactory;
   }
 

packages/core/src/utils/Configuration.ts

@@ -18,6 +18,7 @@ import { EventSubscriber } from '../events';
 import { IDatabaseDriver } from '../drivers/IDatabaseDriver';
 import { EntityOptions } from '../decorators';
 import { NotFoundError } from '../errors';
+import { RequestContext } from './RequestContext';
 
 export class Configuration<D extends IDatabaseDriver = IDatabaseDriver> {
 
@@ -35,6 +36,7 @@ export class Configuration<D extends IDatabaseDriver = IDatabaseDriver> {
     },
     strict: false,
     validate: false,
+    context: () => RequestContext.getEntityManager(),
     // eslint-disable-next-line no-console
     logger: console.log.bind(console),
     findOneOrFailHandler: (entityName: string, where: Dictionary | IPrimaryKey) => NotFoundError.findOneFailed(entityName, where),
@@ -329,6 +331,7 @@ export interface MikroORMOptions<D extends IDatabaseDriver = IDatabaseDriver> ex
   replicas?: Partial<ConnectionOptions>[];
   strict: boolean;
   validate: boolean;
+  context: () => EntityManager | undefined;
   logger: (message: string) => void;
   findOneOrFailHandler: (entityName: string, where: Dictionary | IPrimaryKey) => Error;
   debug: boolean | LoggerNamespace[];

packages/core/src/utils/RequestContext.ts

@@ -1,13 +1,16 @@
 import domain, { Domain } from 'domain';
-import { v4 as uuid } from 'uuid';
 import { EntityManager } from '../EntityManager';
 import { Dictionary } from '../typings';
 
 export type ORMDomain = Domain & { __mikro_orm_context?: RequestContext };
 
+/**
+ * For node 14 and above it is suggested to use `AsyncLocalStorage` instead,
+ * @see https://mikro-orm.io/docs/async-local-storage/
+ */
 export class RequestContext {
 
-  readonly id = uuid();
+  readonly id = this.em.id;
 
   constructor(readonly em: EntityManager) { }