Hybrid applications in NestJS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a NestJS hybrid application that supports both HTTP and WebSocket.

NestJS

import { NestFactory } from '@nestjs/core';
import { AppModule } from './app.module';

async function bootstrap() {
  const app = await NestFactory.[1](AppModule);
  await app.listen(3000);
}
bootstrap();

Drag options to blanks, or click blank then click option'

AcreateMicroservice

BcreateHybridApplication

CcreateWebSocketAdapter

Dcreate

Attempts:

3 left

💡 Hint

Common Mistakes

Using createMicroservice instead of create for hybrid apps.

Trying to use a non-existent method like createHybridApplication.

The NestFactory.create() method creates a NestJS application that supports HTTP by default. To support WebSocket, you need to enable a WebSocket adapter separately.

2fill in blank

medium

Complete the code to enable WebSocket adapter in a NestJS hybrid application.

NestJS

import { NestFactory } from '@nestjs/core';
import { AppModule } from './app.module';
import { IoAdapter } from '@nestjs/platform-socket.io';

async function bootstrap() {
  const app = await NestFactory.create(AppModule);
  app.useWebSocketAdapter(new [1](app));
  await app.listen(3000);
}
bootstrap();

Drag options to blanks, or click blank then click option'

AWsAdapter

BIoAdapter

CSocketAdapter

DWebSocketAdapter

Attempts:

3 left

💡 Hint

Common Mistakes

Using a non-existent adapter like WsAdapter or WebSocketAdapter.

Not passing the app instance to the adapter constructor.

The IoAdapter is the built-in WebSocket adapter for Socket.IO in NestJS.

3fill in blank

hard

Fix the error in the code to properly create a hybrid application with HTTP and microservice support.

NestJS

import { NestFactory } from '@nestjs/core';
import { AppModule } from './app.module';
import { Transport } from '@nestjs/microservices';

async function bootstrap() {
  const app = await NestFactory.create(AppModule);
  app.connectMicroservice({ transport: [1].TCP });
  await app.startAllMicroservices();
  await app.listen(3000);
}
bootstrap();

Drag options to blanks, or click blank then click option'

ATransport

Btransport

CTRANSPORT

DTransporter

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase 'transport' which is undefined.

Using a wrong identifier like 'Transporter'.

The Transport enum is imported and used with uppercase 'T' to specify the transport type.

4fill in blank

hard

Fill both blanks to create a NestJS hybrid app that connects a Redis microservice and listens on port 4000.

NestJS

import { NestFactory } from '@nestjs/core';
import { AppModule } from './app.module';
import { Transport } from '@nestjs/microservices';

async function bootstrap() {
  const app = await NestFactory.[1](AppModule);
  app.connectMicroservice({ transport: [2].REDIS });
  await app.startAllMicroservices();
  await app.listen(4000);
}
bootstrap();

Drag options to blanks, or click blank then click option'

Acreate

BcreateMicroservice

CTransport

Dtransport

Attempts:

3 left

💡 Hint

Common Mistakes

Using createMicroservice instead of create for main app.

Using lowercase 'transport' instead of 'Transport'.

Use create to create the main app and Transport.REDIS to specify Redis microservice transport.

5fill in blank

hard

Fill all three blanks to create a hybrid app with HTTP, connect a TCP microservice, and start both on port 5000.

NestJS

import { NestFactory } from '@nestjs/core';
import { AppModule } from './app.module';
import { Transport } from '@nestjs/microservices';

async function bootstrap() {
  const app = await NestFactory.[1](AppModule);
  app.connectMicroservice({ transport: [2].TCP });
  await app.startAllMicroservices();
  await app.[3](5000);
}
bootstrap();

Drag options to blanks, or click blank then click option'

Acreate

BTransport

Clisten

Dstart

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'start' instead of 'listen' to start the HTTP server.

Using lowercase 'transport' instead of 'Transport'.

Use create to create the app, Transport.TCP for TCP microservice, and listen to start the HTTP server.

Practice

1. What is a hybrid application in NestJS?

easy

A. An app that combines HTTP and microservices in one project

B. An app that only uses HTTP controllers

C. An app that only uses microservices

D. An app that runs on multiple servers

Solution

1. Step 1: Understand NestJS application types

   NestJS apps can be HTTP-based, microservice-based, or both combined.

2. Step 2: Define hybrid application

   A hybrid app combines HTTP and microservices in one project to handle both communication types.

3. Final Answer:

   An app that combines HTTP and microservices in one project -> Option A

4. Quick Check:

   Hybrid app = HTTP + microservices [OK]

Hint: Hybrid means mixing HTTP and microservices in one app [OK]

Common Mistakes:

• Thinking hybrid means multiple servers
• Confusing hybrid with only HTTP or only microservices
• Assuming hybrid apps are separate projects

2. Which method is used to add microservice support in a NestJS hybrid application?

easy

A. connectMicroservice()

B. createMicroservice()

C. addMicroservice()

D. useMicroservice()

Solution

1. Step 1: Recall NestJS microservice integration method

   The official NestJS method to add microservices to an app is connectMicroservice().

2. Step 2: Verify method names

   Other options like createMicroservice(), addMicroservice(), or useMicroservice() are not valid NestJS methods.

3. Final Answer:

   connectMicroservice() -> Option A

4. Quick Check:

   Use connectMicroservice() to add microservices [OK]

Hint: Remember: connectMicroservice() connects microservices [OK]

Common Mistakes:

• Using createMicroservice() which does not exist
• Confusing with addMicroservice() or useMicroservice()
• Trying to add microservices without this method

3. Given this NestJS hybrid app code snippet, what will be the output when the app starts?

const app = await NestFactory.create(AppModule);
app.connectMicroservice({ transport: Transport.TCP });
await app.startAllMicroservices();
await app.listen(3000);
console.log('App is running');

medium

A. App listens on port 3000 but microservices do not start

B. App is running (and microservices start listening)

C. Error: connectMicroservice is not a function

D. App crashes due to missing microservice configuration

Solution

1. Step 1: Analyze microservice connection

   The code calls connectMicroservice with TCP transport, which is valid to add microservices.

2. Step 2: Check microservice start and app listen

   startAllMicroservices() starts microservices, then app.listen(3000) starts HTTP server. Console logs 'App is running'.

3. Final Answer:

   App is running (and microservices start listening) -> Option B

4. Quick Check:

   connectMicroservice + startAllMicroservices + listen = running app [OK]

Hint: connectMicroservice + startAllMicroservices means microservices run [OK]

Common Mistakes:

• Thinking microservices start automatically without startAllMicroservices()
• Confusing connectMicroservice with createMicroservice
• Assuming app.listen blocks microservices

4. Identify the error in this NestJS hybrid app setup:

const app = await NestFactory.create(AppModule);
app.connectMicroservice({ transport: Transport.REDIS });
await app.listen(3000);
await app.startAllMicroservices();

medium

A. AppModule cannot be used with microservices

B. connectMicroservice() does not accept transport option

C. startAllMicroservices() must be called before app.listen()

D. Missing await before connectMicroservice()

Solution

1. Step 1: Check method call order

   In NestJS, microservices must be started before the HTTP server listens, so startAllMicroservices() should be before app.listen().

2. Step 2: Validate other options

   connectMicroservice() accepts transport option; AppModule supports microservices; connectMicroservice() is synchronous, no await needed.

3. Final Answer:

   startAllMicroservices() must be called before app.listen() -> Option C

4. Quick Check:

   Start microservices before HTTP listen [OK]

Hint: Call startAllMicroservices() before app.listen() [OK]

Common Mistakes:

• Calling startAllMicroservices() after app.listen()
• Adding await to connectMicroservice()
• Thinking transport option is invalid

5. You want to build a NestJS hybrid app that handles HTTP requests and listens to RabbitMQ messages. Which steps correctly set up the microservice part?

hard

A. Use connectMicroservice({ transport: Transport.TCP }) and call startAllMicroservices() after app.listen()

B. Use createMicroservice({ transport: Transport.RMQ }) and call app.listen() before starting microservices

C. Add RabbitMQ config in AppModule imports and call app.listen() only

D. Use connectMicroservice({ transport: Transport.RMQ, options: { urls: ['amqp://localhost'], queue: 'main_queue' } }), then call startAllMicroservices() before app.listen()

Solution

1. Step 1: Choose correct microservice setup for RabbitMQ

   connectMicroservice() with Transport.RMQ and proper options (urls, queue) is the correct way to add RabbitMQ microservice.

2. Step 2: Call startAllMicroservices() before app.listen()

   Microservices must start before HTTP server listens to ensure both run properly.

3. Final Answer:

   Use connectMicroservice({ transport: Transport.RMQ, options: { urls: ['amqp://localhost'], queue: 'main_queue' } }), then call startAllMicroservices() before app.listen() -> Option D

4. Quick Check:

   connectMicroservice + RMQ options + startAllMicroservices before listen [OK]

Hint: Set RMQ options in connectMicroservice and start microservices first [OK]

Common Mistakes:

• Using createMicroservice() which is not a NestFactory method
• Calling app.listen() before starting microservices
• Using wrong transport type for RabbitMQ
• Not providing RabbitMQ connection options