feat(medusa,event-bus-local,event-bus-redis): Event Bus modules (#2599)

packages/event-bus-local/.gitignore

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+/dist
+node_modules
+.DS_store
+.env*
+.env
+*.sql

packages/event-bus-local/README.md

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+<p align="center">
+  <a href="https://www.medusajs.com">
+    <img alt="Medusa" src="https://user-images.githubusercontent.com/7554214/153162406-bf8fd16f-aa98-4604-b87b-e13ab4baf604.png" width="100" />
+  </a>
+</p>
+<h1 align="center">
+  @medusajs/event-bus-local
+</h1>
+
+<h4 align="center">
+  <a href="https://docs.medusajs.com">Documentation</a> |
+  <a href="https://www.medusajs.com">Website</a>
+</h4>
+
+<p align="center">
+An open source composable commerce engine built for developers.
+</p>
+<p align="center">
+  <a href="https://github.com/medusajs/medusa/blob/master/LICENSE">
+    <img src="https://img.shields.io/badge/license-MIT-blue.svg" alt="Medusa is released under the MIT license." />
+  </a>
+  <a href="https://circleci.com/gh/medusajs/medusa">
+    <img src="https://circleci.com/gh/medusajs/medusa.svg?style=shield" alt="Current CircleCI build status." />
+  </a>
+  <a href="https://github.com/medusajs/medusa/blob/master/CONTRIBUTING.md">
+    <img src="https://img.shields.io/badge/PRs-welcome-brightgreen.svg?style=flat" alt="PRs welcome!" />
+  </a>
+    <a href="https://www.producthunt.com/posts/medusa"><img src="https://img.shields.io/badge/Product%20Hunt-%231%20Product%20of%20the%20Day-%23DA552E" alt="Product Hunt"></a>
+  <a href="https://discord.gg/xpCwq3Kfn8">
+    <img src="https://img.shields.io/badge/chat-on%20discord-7289DA.svg" alt="Discord Chat" />
+  </a>
+  <a href="https://twitter.com/intent/follow?screen_name=medusajs">
+    <img src="https://img.shields.io/twitter/follow/medusajs.svg?label=Follow%20@medusajs" alt="Follow @medusajs" />
+  </a>
+</p>
+
+## Overview
+
+Local Event Bus module for Medusa. When installed, the events system of Medusa is powered by the Node EventEmitter. This module installed by default in new (> v1.8.0) Medusa projects.
+
+The Node EventEmitter is limited to a single process environment. We generally recommend using the `@medusajs/event-bus-redis` module in a production environment. 
+
+## Getting started
+
+Install the module:
+
+```bash
+yarn add @medusajs/event-bus-local
+```
+
+You don't need to add the module to your project configuration as it is the default one. Medusa will try to use it, if no other event buses are installed. 
+
+```js
+module.exports = {
+  // ...
+  modules: [ ... ],
+  // ...
+}
+```
+
+## Configuration
+
+The module comes with no configuration options.

packages/event-bus-local/jest.config.js

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+module.exports = {
+  globals: {
+    "ts-jest": {
+      tsConfig: "tsconfig.spec.json",
+      isolatedModules: false,
+    },
+  },
+  transform: {
+    "^.+\\.[jt]s?$": "ts-jest",
+  },
+  testEnvironment: `node`,
+  moduleFileExtensions: [`js`, `jsx`, `ts`, `tsx`, `json`],
+}

packages/event-bus-local/package.json

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+{
+  "name": "@medusajs/event-bus-local",
+  "version": "0.1.0",
+  "description": "Local Event Bus Module for Medusa",
+  "main": "dist/index.js",
+  "files": [
+    "dist"
+  ],
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/medusajs/medusa",
+    "directory": "packages/event-bus-local"
+  },
+  "publishConfig": {
+    "access": "public"
+  },
+  "author": "Medusa",
+  "license": "MIT",
+  "devDependencies": {
+    "@medusajs/types": "^0.0.1",
+    "cross-env": "^5.2.1",
+    "jest": "^25.5.2",
+    "ts-jest": "^25.5.1",
+    "typescript": "^4.4.4"
+  },
+  "scripts": {
+    "watch": "tsc --build --watch",
+    "prepare": "cross-env NODE_ENV=production yarn run build",
+    "build": "tsc --build",
+    "test": "jest --passWithNoTests",
+    "test:unit": "jest --passWithNoTests"
+  },
+  "dependencies": {
+    "@medusajs/modules-sdk": "*",
+    "@medusajs/utils": "^0.0.1"
+  }
+}

packages/event-bus-local/src/index.ts

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+import { ModuleExports } from "@medusajs/modules-sdk"
+import Loader from "./loaders"
+import LocalEventBus from "./services/event-bus-local"
+
+export const service = LocalEventBus
+export const loaders = [Loader]
+
+const moduleDefinition: ModuleExports = {
+  service,
+  loaders,
+}
+
+export default moduleDefinition

packages/event-bus-local/src/loaders/index.ts

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+import { LoaderOptions } from "@medusajs/modules-sdk"
+
+
+export default async ({ logger }: LoaderOptions): Promise<void> => {
+  logger?.warn(
+    "Local Event Bus installed. This is not recommended for production."
+  )
+}

packages/event-bus-local/src/services/__tests__/event-bus-local.js

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+import LocalEventBusService from "../event-bus-local"
+
+jest.genMockFromModule("events")
+jest.mock("events")
+
+const loggerMock = {
+  info: jest.fn().mockReturnValue(console.log),
+  warn: jest.fn().mockReturnValue(console.log),
+  error: jest.fn().mockReturnValue(console.log),
+}
+
+const moduleDeps = {
+  logger: loggerMock,
+}
+
+describe("LocalEventBusService", () => {
+  let eventBus
+
+  describe("emit", () => {
+    describe("Successfully emits events", () => {
+      beforeEach(() => {
+        jest.clearAllMocks()
+      })
+
+      it("Emits an event", () => {
+        eventBus = new LocalEventBusService(
+          moduleDeps,
+          {},
+          {
+            resources: "shared",
+          }
+        )
+
+        eventBus.eventEmitter_.emit.mockImplementationOnce((data) => data)
+
+        eventBus.emit("eventName", { hi: "1234" })
+
+        expect(eventBus.eventEmitter_.emit).toHaveBeenCalledTimes(1)
+        expect(eventBus.eventEmitter_.emit).toHaveBeenCalledWith("eventName", {
+          hi: "1234",
+        })
+      })
+
+      it("Emits multiple events", () => {
+        eventBus = new LocalEventBusService(
+          moduleDeps,
+          {},
+          {
+            resources: "shared",
+          }
+        )
+
+        eventBus.eventEmitter_.emit.mockImplementationOnce((data) => data)
+
+        eventBus.emit([
+          { eventName: "event-1", data: { hi: "1234" } },
+          { eventName: "event-2", data: { hi: "5678" } },
+        ])
+
+        expect(eventBus.eventEmitter_.emit).toHaveBeenCalledTimes(2)
+        expect(eventBus.eventEmitter_.emit).toHaveBeenCalledWith("event-1", {
+          hi: "1234",
+        })
+        expect(eventBus.eventEmitter_.emit).toHaveBeenCalledWith("event-2", {
+          hi: "5678",
+        })
+      })
+    })
+  })
+})

packages/event-bus-local/src/services/event-bus-local.ts

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+import { Logger, MedusaContainer } from "@medusajs/modules-sdk"
+import { EmitData, Subscriber } from "@medusajs/types"
+import { AbstractEventBusModuleService } from "@medusajs/utils"
+import { EventEmitter } from "events"
+
+type InjectedDependencies = {
+  logger: Logger
+}
+
+const eventEmitter = new EventEmitter()
+
+export default class LocalEventBusService extends AbstractEventBusModuleService {
+  protected readonly logger_: Logger
+  protected readonly eventEmitter_: EventEmitter
+
+  constructor({ logger }: MedusaContainer & InjectedDependencies) {
+    // @ts-ignore
+    super(...arguments)
+
+    this.logger_ = logger
+    this.eventEmitter_ = eventEmitter
+  }
+
+  async emit<T>(
+    eventName: string,
+    data: T,
+    options: Record<string, unknown>
+  ): Promise<void>
+
+  /**
+   * Emit a number of events
+   * @param {EmitData} data - the data to send to the subscriber.
+   */
+  async emit<T>(data: EmitData<T>[]): Promise<void>
+
+  async emit<T, TInput extends string | EmitData<T>[] = string>(
+    eventOrData: TInput,
+    data?: T,
+    options: Record<string, unknown> = {}
+  ): Promise<void> {
+    const isBulkEmit = Array.isArray(eventOrData)
+
+    const events: EmitData[] = isBulkEmit
+      ? eventOrData
+      : [{ eventName: eventOrData, data }]
+
+    for (const event of events) {
+      const eventListenersCount = this.eventEmitter_.listenerCount(
+        event.eventName
+      )
+
+      this.logger_.info(
+        `Processing ${event.eventName} which has ${eventListenersCount} subscribers`
+      )
+      
+      if (eventListenersCount === 0) {
+        continue
+      }
+
+
+      try {
+        this.eventEmitter_.emit(event.eventName, event.data)
+      } catch (error) {
+        this.logger_.error(
+          `An error occurred while processing ${event.eventName}: ${error}`
+        )
+      }
+    }
+  }
+
+  subscribe(event: string | symbol, subscriber: Subscriber): this {
+    this.eventEmitter_.on(event, subscriber)
+    return this
+  }
+
+  unsubscribe(event: string | symbol, subscriber: Subscriber): this {
+    this.eventEmitter_.off(event, subscriber)
+    return this
+  }
+}

packages/event-bus-local/tsconfig.json

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+{
+  "compilerOptions": {
+    "lib": ["es5", "es6", "es2019"],
+    "target": "es6",
+    "outDir": "./dist",
+    "esModuleInterop": true,
+    "declaration": true,
+    "module": "commonjs",
+    "moduleResolution": "node",
+    "emitDecoratorMetadata": true,
+    "experimentalDecorators": true,
+    "sourceMap": true,
+    "noImplicitReturns": true,
+    "strictNullChecks": true,
+    "strictFunctionTypes": true,
+    "noImplicitThis": true,
+    "allowJs": true,
+    "skipLibCheck": true,
+    "downlevelIteration": true // to use ES5 specific tooling
+  },
+  "include": ["src"],
+  "exclude": [
+    "dist",
+    "./src/**/__tests__",
+    "./src/**/__mocks__",
+    "./src/**/__fixtures__",
+    "node_modules"
+  ]
+}

packages/event-bus-local/tsconfig.spec.json

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+{
+  "extends": "./tsconfig.json",
+  "include": ["src"],
+  "exclude": ["node_modules"]
+}