Logging with Winston or Pino in NestJS - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of this Winston logger configuration?

Given this NestJS Winston logger setup, what will be logged when calling logger.info('Server started')?

NestJS

import { WinstonModule } from 'nest-winston';
import * as winston from 'winston';

const logger = WinstonModule.createLogger({
  transports: [
    new winston.transports.Console({
      level: 'info',
      format: winston.format.combine(
        winston.format.timestamp(),
        winston.format.printf(({ level, message, timestamp }) => `${timestamp} ${level}: ${message}`)
      )
    })
  ]
});

logger.info('Server started');

A info: Server started

B 2024-06-01T12:00:00.000Z info: Server started

C Server started

D Error: logger.info is not a function

💡 Hint

Look at the format used in the Console transport.

The logger uses a timestamp and printf format, so the output includes the ISO timestamp, the log level, and the message.

❓ Configuration

intermediate

Which Pino configuration enables pretty printing in NestJS?

Choose the correct Pino logger configuration snippet to enable pretty printing (human-readable logs) in a NestJS application.

A

import pino from 'pino';
const logger = pino({ format: 'pretty' });

B

import pino from 'pino';
const logger = pino({ prettyPrint: true });

C

import pino from 'pino';
const logger = pino({ transport: { target: 'pino-pretty' } });

D

import pino from 'pino';
const logger = pino({ pretty: true });

💡 Hint

Check the latest Pino documentation for pretty printing options.

Since Pino v7, pretty printing is enabled via the transport option with target: 'pino-pretty'.

❓ Troubleshoot

advanced

Why does this Winston logger not output any logs?

Consider this Winston logger setup in NestJS. Why does calling logger.info('Failure') produce no output?

NestJS

import { WinstonModule } from 'nest-winston';
import * as winston from 'winston';

const logger = WinstonModule.createLogger({
  transports: [
    new winston.transports.Console({ level: 'warn' })
  ]
});

logger.info('Failure');

A Because the transport level is set to 'warn', and 'info' is lower priority so it does not log.

B Because the transport level is set to 'warn', and 'info' is a higher priority so it should log.

C Because the transport level is set to 'warn', but the logger instance is not properly created.

D Because the transport level is set to 'warn', and 'info' is higher priority so it logs.

💡 Hint

Remember the log level priorities: error > warn > info.

Log levels in Winston have priorities (lower number = higher priority): 'error'(0) > 'warn'(1) > 'info'(2). With transport level 'warn', only 'warn' and 'error' log, not 'info'.

🔀 Workflow

advanced

What is the correct order to integrate Pino logger in a NestJS app?

Arrange these steps in the correct order to add Pino logging to a NestJS application.

A 2,1,3,4

B 3,1,2,4

C 1,3,2,4

D 1,2,3,4

💡 Hint

Think about installation before usage.

You first install packages, then import the module, configure it, and finally use the logger service.

✅ Best Practice

expert

Which practice improves performance when using Pino in production?

Choose the best practice to improve logging performance in a production NestJS app using Pino.

A Use asynchronous logging with a separate process or transport for log writing

B Disable logging completely in production to avoid overhead

C Use synchronous logging to ensure all logs are written immediately

D Log all debug and trace level messages in production for full details

💡 Hint

Think about how to reduce blocking operations in production.

Asynchronous logging offloads log writing to a separate process, reducing app blocking and improving performance.