NestJS: Setting up file logging daily rotation with winston

Nest Provides a default logger and that’s fine when developing.
But if you want to go further, I recommend using winston, and with nest-winston package we can easily replace the default logger.

Installing nest-winston

npm install --save winston
npm install --save nest-winston

Using winston logger instead of NestJS’s one

We configure the logger used by our App when bootstrapping:

main.ts

import { NestFactory } from '@nestjs/core';
import { ValidationPipe } from '@nestjs/common';
import { WinstonModule } from 'nest-winston';
import { transports, format } from 'winston';

import { AppModule } from './app.module';

async function bootstrap() {
  const app = await NestFactory.create(AppModule, {
    logger: WinstonModule.createLogger({
      transports: [
     // let's log errors into its own file
        new transports.File({
          filename: `logs/error.log`,
          level: 'error',
          format: format.combine(format.timestamp(), format.json()),
        }),
        // logging all level
        new transports.File({
          filename: `logs/combined.log`,
          format: format.combine(format.timestamp(), format.json()),
        }),
        // we also want to see logs in our console
        new transports.Console({
         format: format.combine(
           format.cli(),
           format.splat(),
           format.timestamp(),
           format.printf((info) => {
             return `${info.timestamp} ${info.level}: ${info.message}`;
           }),
          ),
      }),
      ],
    }),
  });
  await app.listen(3000);
}
bootstrap();

This configuration will output:
- error logs into logs/error.log
- all logs (info, warning, debug, error…) into logs/combined.log
- also also logs level into the console.

Nice! But what about file rotation ? Let’s see it now ↓

Adding log rotation

Install winston-daily-rotate-file package

npm install winston-daily-rotate-file

Now, let’s change main.ts to add log rotation:

// we need to import it to make transports.DailyRotate is available
import 'winston-daily-rotate-file'; 

async function bootstrap() {
  const app = await NestFactory.create(AppModule, {
    logger: WinstonModule.createLogger({
      transports: [
        // file on daily rotation (error only)
        new transports.DailyRotateFile({
       // %DATE will be replaced by the current date
          filename: `logs/%DATE%-error.log`, 
          level: 'error',
          format: format.combine(format.timestamp(), format.json()),
          datePattern: 'YYYY-MM-DD',
          zippedArchive: false, // don't want to zip our logs
          maxFiles: '30d', // will keep log until they are older than 30 days
        }),
        // same for all levels
        new transports.DailyRotateFile({
          filename: `logs/%DATE%-combined.log`,
          format: format.combine(format.timestamp(), format.json()),
          datePattern: 'YYYY-MM-DD',
          zippedArchive: false,
          maxFiles: '30d',
        }),
        new transports.Console({
         format: format.combine(
           format.cli(),
           format.splat(),
           format.timestamp(),
           format.printf((info) => {
             return `${info.timestamp} ${info.level}: ${info.message}`;
           }),
          ),
      }),
      ],
    }),
  });
  await app.listen(3000);
}

That it for logs rotation.
Now at the root of your app when you run it you should see a folder named “logs” containing `YYYY-MM-DD-error.log` and `YYYY-MM-DD-combined.log`. YYYY-MM-DD being replaced by the actual date. So as I’m writing this post we are the 10th of mars 2023, my error log file will be named : 2023–03–10-error.log

Logging 404 , 401, 400 errors

By default Nest doesn’t log Bad Request, 401 Unauthorized, nor 405 Method Not Allowed. And that’s a shame 😛!

The simplest way I found to get those logged is to use a middleware:

request-logger.middleware.ts

import { Injectable, Logger, NestMiddleware } from '@nestjs/common';
import { Request, Response, NextFunction } from 'express';

@Injectable()
export class RequestLoggerMiddleware implements NestMiddleware {
  private readonly logger = new Logger();

  use(req: Request, res: Response, next: NextFunction) {
    res.on('finish', () => {
      const statusCode = res.statusCode;
      if (statusCode === 401 || statusCode === 404 || statusCode === 405) {
        this.logger.warn(`[${req.method}] ${req.url} - ${statusCode}`);
      }
    });

    next();
  }
}

Now let’s apply our middleware to our app module:

app.module.ts

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

import { AppController } from './app.controller';
import { RequestLoggerMiddleware } from '../middleware/request-logger.middleware';
@Module({
  controllers: [AppController],
  providers: [],
})
export class AppModule {
  // let's add a middleware on all routes
  configure(consumer: MiddlewareConsumer) {
    consumer.apply(RequestLoggerMiddleware).forRoutes('*');
  }
}

Conclusion

File logging isn’t too hard to setup and improves our NestJs API by:
- helping with debugging
- monitoring performance (if you put metrics you can track)
- improving security by monitor unauthorized access attempts

That’s it! Thank you for reading