[Question] Custom logger

[szkumorowski]

Is it possible to inject custom logger into nest components ?

[szkumorowski]

@chadjaros Totally agree

Best way and the simplest one - to forward on this topic is allow set for Nest

• LoggerFactory or class which implementes Nest logger interface

Then developers could do whatever they would like to do in this topic (disable, change colors which causes as well the errors on linux environments). Like in: http://typeorm.io/#/logging

[kamilmysliwiec]

Since v4.6.1 you can use your own logger implementation instead of default built-in one:

const app = await NestFactory.create(ApplicationModule, {
    logger: new Logger(),
});

The Logger class has to implement LoggerService interface (@nestjs/common), for example:

class Logger implements LoggerService {
  log(message: string) {
    console.log(message);
  }
  error(message: string, trace: string) {
    console.error(message);
  }
  warn(message: string) {
    console.warn(message);
  }
}

[chanlito]

@kamilmysliwiec nice 🍾

[chadjaros]

Thank you! This is exactly what I wanted.

[cojack]

@kamilmysliwiec but this class is out of Nest scope, and there is no possibility to inject some services inside, Am I right?

[kamilmysliwiec]

@cojack yes, and actually it cannot be a part of Nest scope. This feature is only to provide an ability to override default logger (disable bootstrap messages/transport them elsewhere/etc.), it works independently. Logger starts to log messages before even 1 instance from Nest scope is instantiated. However, you are still able to use the same logger instance in Nest scope as well as a default logger, just provide it using useValue.

[BorntraegerMarc]

I didn't find any documentation about the custom logger feature on the official website. Is there already an open issue to add the docs for this new feature?

[cojack]

@kamilmysliwiec hmmm sound interesting. Please put this example in documentation.

[FrancisVarga]

Any documentation or example for this?

[shekohex]

@FrancisVarga Check this Comment https://github.com/nestjs/nest/issues/507#comment-374221089

[jsdevtom]

In large angular projects, I have had the experience of providing your logger in a common modules as detailed below. This has the advantage of a coherent logging when you also pass the logger to the NestFactory as @kamilmysliwiec details above:

common.module.ts

import { Module } from '@nestjs/common';
import { ConsoleLogger } from '../logger/logger';

const services = [
  ConsoleLogger,
];

@Module({
  providers: [
    ...services,
  ],
  exports: [
    ...services,
  ],
})
export class CommonModule {
}

where the logger looks like this:

logger.ts

import { Injectable, LoggerService } from '@nestjs/common';
import chalk from 'chalk';

@Injectable()
export class ConsoleLogger implements LoggerService {
  log(...messages: any[]) {
    // tslint:disable-next-line:no-console
    console.log(chalk.green(`log: [${ConsoleLogger.time()}]`), ...messages);
  }
  error(...messages: any[]) {
    // tslint:disable-next-line:no-console
    console.error(chalk.red(`error: [${ConsoleLogger.time()}]`), ...messages);
  }
  warn(...messages: any[]) {
    // tslint:disable-next-line:no-console
    console.warn(chalk.yellow(`warn: [${ConsoleLogger.time()}]`), ...messages);
  }
}

Then just inject the common module where you need it like so:

example.module.ts

import { Module } from '@nestjs/common';
import { ShopController } from './shop.controller';
import { ShopService } from './shop.service';
import { CommonModule } from '../common/common.module';

@Module({
  imports: [CommonModule],
  controllers: [ShopController],
  providers: [ShopService],
})
export class ShopModule {
}

and finally use it:

example.controller.ts

@Controller('example')
export class ShopController {

  constructor(
    private logger: ConsoleLogger,
  ) {

  @Get()
  root(): string {
    this.logger.log('hi'); // results in: log: [Sat, 23 Jun 2018 08:58:27 GMT] hi
  }

}

[lock[bot]]

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