nest-winston

A Nest module wrapper for winston logger.

Table of Contents

• Installation
• Quick start
• Async configuration
• Replacing the Nest logger
• Replacing the Nest logger (also for bootstrapping)
• Injection and usage summary
• Utilities
• Logger methods
• Upgrade
• Contributing
• License

Installation

npm install --save nest-winston winston

Having troubles configuring nest-winston? Clone this repository and cd in a sample:

cd sample/quick-start
npm install
npm run start:dev

If you want to upgrade to a major or minor version, have a look at the upgrade section.

Quick start

Import WinstonModule into the root AppModule and use the forRoot() method to configure it. This method accepts the same options object as createLogger() function from the winston package:

import { Module } from '@nestjs/common';
import { WinstonModule } from 'nest-winston';
import * as winston from 'winston';

@Module({
  imports: [
    WinstonModule.forRoot({
      // options
    }),
  ],
})
export class AppModule {}

Afterward, the winston instance will be available to inject across entire project (and in your feature modules, being WinstonModule a global one) using the WINSTON_MODULE_PROVIDER injection token:

import { Controller, Inject } from '@nestjs/common';
import { WINSTON_MODULE_PROVIDER } from 'nest-winston';
import { Logger } from 'winston';

@Controller('cats')
export class CatsController {
  constructor(@Inject(WINSTON_MODULE_PROVIDER) private readonly logger: Logger) { }
}

Async configuration

> Caveats: because the way Nest works, you can't inject dependencies exported from the root module itself (using exports). If you use forRootAsync() and need to inject a service, that service must be either imported using the imports options or exported from a global module.

Maybe you need to asynchronously pass your module options, for example when you need a configuration service. In such case, use the forRootAsync() method, returning an options object from the useFactory method:

import { Module } from '@nestjs/common';
import { WinstonModule } from 'nest-winston';
import * as winston from 'winston';

@Module({
  imports: [
    WinstonModule.forRootAsync({
      useFactory: () => ({
        // options
      }),
      inject: [],
    }),
  ],
})
export class AppModule {}

The factory might be async, can inject dependencies with inject option and import other modules using the imports option.

Alternatively, you can use the useClass syntax:

WinstonModule.forRootAsync({
  useClass: WinstonConfigService,
})

With the above code, Nest will create a new instance of WinstonConfigService and its method createWinstonModuleOptions will be called in order to provide the module options.

Replacing the Nest logger

This module also provides the WinstonLogger class (custom implementation of the LoggerService interface) to be used by Nest for system logging. This will ensure consistent behavior and formatting across both Nest system logging and your application event/message logging.

Change your main.ts as shown below:

import { WINSTON_MODULE_NEST_PROVIDER } from 'nest-winston';

async function bootstrap() {
  const app = await NestFactory.create(AppModule);
  app.useLogger(app.get(WINSTON_MODULE_NEST_PROVIDER));
  await app.listen(3000);
}
bootstrap();

Then inject the logger using the WINSTON_MODULE_NEST_PROVIDER token and the LoggerService typing:

import { Controller, Inject, LoggerService } from '@nestjs/common';
import { WINSTON_MODULE_NEST_PROVIDER } from 'nest-winston';

@Controller('cats')
export class CatsController {
  constructor(@Inject(WINSTON_MODULE_NEST_PROVIDER) private readonly logger: LoggerService) { }
}

Under the hood, the WinstonLogger class uses the configured winston logger instance (through forRoot or forRootAsync), forwarding all calls to it.

Replacing the Nest logger (also for bootstrapping)

> Important: by doing this, you give up the dependency injection, meaning that forRoot and forRootAsync are not needed and shouldn't be used. Remove them from your main module.

Using the dependency injection has one minor drawback. Nest has to bootstrap the application first (instantiating modules and providers, injecting dependencies, etc.) and during this process the instance of WinstonLogger is not yet available, which means that Nest falls back to the internal logger.

One solution is to create the logger outside of the application lifecycle, using the createLogger function, and pass it to NestFactory.create. Nest will then wrap our winston logger (the same instance returned by the createLogger method) into the Logger class, forwarding all calls to it:

import { WinstonModule } from 'nest-winston';

async function bootstrap() {
  const app = await NestFactory.create(AppModule, {
    logger: WinstonModule.createLogger({
      // options (same as WinstonModule.forRoot() options)
    })
  });
  await app.listen(3000);
}
bootstrap();

An alternative is to provide directly an instance of Winston in the options. This allows you to keep a reference to the instance and interact with it.

import { createLogger } from 'winston';
import { WinstonModule } from 'nest-winston';

async function bootstrap() {
  // createLogger of Winston
  const instance = createLogger({
    // options of Winston
  });
  const app = await NestFactory.create(AppModule, {
    logger: WinstonModule.createLogger({
      instance,
    }),
  });
  await app.listen(3000);
}
bootstrap();

The usage afterwards for both solutions is the same. First, change your main module to provide the Logger service:

import { Logger, Module } from '@nestjs/common';

@Module({
  providers: [Logger],
})
export class AppModule {}

Then inject the logger simply by type hinting it with Logger from @nestjs/common:

import { Controller, Logger } from '@nestjs/common';

@Controller('cats')
export class CatsController {
  constructor(private readonly logger: Logger) {}
}

Alternative syntax using the LoggerService typing and the @Inject decorator:

import { Controller, Inject, Logger, LoggerService } from '@nestjs/common';

@Controller('cats')
export class CatsController {
  constructor(@Inject(Logger) private readonly logger: LoggerService) {}
}

Injection and usage summary

Here is a summary of the three techniques explained above:

Utilities

The module also provides a custom Nest-like special formatter for console transports named nestLike. Supported options:

• colors: enable console colors, defaults to true, unless process.env.NO_COLOR is set (same behaviour of Nest > 7.x)
• prettyPrint: pretty format log metadata, defaults to true
• processId: includes the Node Process ID (process.pid) in the output, defaults to true
• appName: includes the provided application name in the output, defaults to true

import { Module } from '@nestjs/common';
import { utilities as nestWinstonModuleUtilities, WinstonModule } from 'nest-winston';
import * as winston from 'winston';

@Module({
  imports: [
    WinstonModule.forRoot({
      transports: [
        new winston.transports.Console({
          format: winston.format.combine(
            winston.format.timestamp(),
            winston.format.ms(),
            nestWinstonModuleUtilities.format.nestLike('MyApp', {
              colors: true,
              prettyPrint: true,
              processId: true,
              appName: true,
            }),
          ),
        }),
        // other transports...
      ],
      // other options
    }),
  ],
})
export class AppModule {}

Logger methods

> Note: the logger instance has different logger methods, and each takes different arguments. To make sure the logger is being formatted the same way across the board take note of the following:

debug(message: any, context?: string)
log(message: any, context?: string)
error(message: any, stack?: string, context?: string)
fatal(message: any, stack?: string, context?: string)
verbose(message: any, context?: string)
warn(message: any, context?: string)

Example:

import { Controller, Get, Logger } from '@nestjs/common';
import { AppService } from './app.service';

@Controller()
export class AppController {
  constructor(
    private readonly appService: AppService,
    private readonly logger: Logger,
  ) {}

  @Get()
  getHello(): string {
    this.logger.log('Calling getHello()', AppController.name);
    this.logger.debug('Calling getHello()', AppController.name);
    this.logger.verbose('Calling getHello()', AppController.name);
    this.logger.warn('Calling getHello()', AppController.name);

    try {
      throw new Error()
    } catch (e) {
      this.logger.error('Calling getHello()', e.stack, AppController.name);
    }

    return this.appService.getHello();
  }
}

Upgrade

Some notes about upgrading to a major or minor version.

1.6.x to 1.7

• The exported type NestLikeConsoleFormatOptions has slightly changed: prettyPrint is now optional and colors has been added.
• The nestLike formatter has the new colors option: if not provided, colors will be used according to Nest "approach" (disabled if env variable process.env.NO_COLOR is defined). Before output was always colorized.

Contributing

All types of contributions are encouraged and valued. See the Contributing guidelines, the community looks forward to your contributions!

License

This project is released under the under terms of the ISC License.