Health checks (Terminus) in NestJS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the TerminusModule in a NestJS module.

NestJS

import { Module } from '@nestjs/common';
import { [1] } from '@nestjs/terminus';

@Module({
  imports: [[1]],
})
export class AppModule {}

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

AHealthCheckModule

BHealthModule

CTerminusModule

DHealthTerminus

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect module names like HealthModule or HealthCheckModule.

Forgetting to import the TerminusModule.

The TerminusModule is the official NestJS module for health checks and must be imported to use Terminus features.

2fill in blank

medium

Complete the code to create a health check endpoint using Terminus in a controller.

NestJS

import { Controller, Get } from '@nestjs/common';
import { HealthCheck, HealthCheckService } from '@nestjs/terminus';

@Controller('health')
export class HealthController {
  constructor(private health: HealthCheckService) {}

  @Get()
  @HealthCheck()
  check() {
    return this.health.[1]([]);
  }
}

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

Aexecute

Brun

Cperform

Dcheck

Attempts:

3 left

💡 Hint

Common Mistakes

Using methods like run() or execute() which do not exist on HealthCheckService.

Forgetting to call the method as a function.

The HealthCheckService provides a method called check() to run all registered health indicators.

3fill in blank

hard

Fix the error in the health indicator registration by completing the code.

NestJS

import { Injectable } from '@nestjs/common';
import { HealthIndicator, HealthIndicatorResult, HealthCheckError } from '@nestjs/terminus';

@Injectable()
export class DiskHealthIndicator extends HealthIndicator {
  async isHealthy(key: string): Promise<HealthIndicatorResult> {
    const diskFree = 100; // pretend value
    const isHealthy = diskFree > 50;
    if (!isHealthy) {
      throw new HealthCheckError('Disk space too low', [1]);
    }
    return this.getStatus(key, isHealthy, { diskFree });
  }
}

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

Athis.getStatus(key, isHealthy, { diskFree })

Bthis.getStatus(key, false, { diskFree })

Cthis.getStatus(key, true, { diskFree })

Dthis.getStatus(key, isHealthy)

Attempts:

3 left

💡 Hint

Common Mistakes

Passing incomplete or incorrect status objects to HealthCheckError.

Omitting the third argument with details.

The HealthCheckError requires the health indicator result object, which is returned by getStatus with the current health state and details.

4fill in blank

hard

Fill both blanks to add a memory health indicator to the health check controller.

NestJS

import { Controller, Get } from '@nestjs/common';
import { HealthCheck, HealthCheckService, [1] } from '@nestjs/terminus';

@Controller('health')
export class HealthController {
  constructor(
    private health: HealthCheckService,
    private [2]: MemoryHealthIndicator
  ) {}

  @Get('memory')
  @HealthCheck()
  checkMemory() {
    return this.health.check([
      () => this.[2].checkHeap('memory_heap'),
    ]);
  }
}

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

AMemoryHealthIndicator

BMemoryIndicator

CMemoryCheck

DMemoryHealth

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect class names like MemoryIndicator or MemoryCheck.

Mismatching the injected variable name and the class.

MemoryHealthIndicator is the official class to check memory usage in Terminus and must be imported and injected with the same name.

5fill in blank

hard

Fill all three blanks to create a custom health indicator and register it in the health check controller.

NestJS

import { Injectable } from '@nestjs/common';
import { HealthIndicator, HealthIndicatorResult, HealthCheckError } from '@nestjs/terminus';

@Injectable()
export class [1] extends HealthIndicator {
  async isHealthy(key: string): Promise<HealthIndicatorResult> {
    const serviceUp = true; // pretend check
    const isHealthy = serviceUp;
    if (!isHealthy) {
      throw new HealthCheckError('Service down', this.getStatus(key, isHealthy));
    }
    return this.getStatus(key, isHealthy);
  }
}

import { Controller, Get } from '@nestjs/common';
import { HealthCheck, HealthCheckService } from '@nestjs/terminus';

@Controller('health')
export class HealthController {
  constructor(
    private health: HealthCheckService,
    private [2]: [1]
  ) {}

  @Get('custom')
  @HealthCheck()
  checkCustom() {
    return this.health.check([
      () => this.[2].isHealthy('custom_service'),
    ]);
  }
}

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

ACustomHealthIndicator

BcustomHealthIndicator

CCustomIndicator

DcustomIndicator

Attempts:

3 left

💡 Hint

Common Mistakes

Using inconsistent names between class and injected variable.

Calling wrong methods or using wrong variable names.

The custom health indicator class is named CustomHealthIndicator, and the injected variable uses camelCase customHealthIndicator. The method isHealthy is called on the injected instance.