如何在NestJS中配置多个Winston日志器实现指定传输端输出？

• 方法签名与Nest内置LoggerService接口不匹配：你自定义的log、error方法参数顺序和Nest要求的不一致，导致你传入的配置对象被识别为上下文参数，无法正确判断输出目标。
• 缺失日志级别兜底配置：Winston实例未显式配置输出级别，默认仅输出info及以上级别的日志，如果传入的自定义level低于该等级会被直接过滤。
• error方法逻辑缺失trace参数处理：现有实现中完全丢弃了trace参数，不符合日志规范的同时可能触发参数校验异常。
• 未补全LoggerService要求的所有方法：Nest日志服务要求实现warn、debug、verbose等方法，缺失会导致部分场景下调用异常。

1. 修正CustomLogger实现 #

import { Injectable, LoggerService } from '@nestjs/common';
import winston from 'winston';
import { WinstonModule } from 'nest-winston';

@Injectable()
export class CustomLogger implements LoggerService {
  // 显式配置日志输出级别，可根据需求调整
  private readonly fileLogger = WinstonModule.createLogger({
    level: 'debug', // 允许输出debug及以上级别的日志
    transports: [
      new winston.transports.File({ filename: "combined.log" })
    ]
  });
  private readonly consoleLogger = WinstonModule.createLogger({
    level: 'debug',
    transports: [
      new winston.transports.Console(),
    ]
  });

  // 适配Nest LoggerService的标准参数签名：message, context?, ...rest
  log(message: any, context?: string, ...optionalParams: any[]) {
    // 提取配置对象：如果第二个参数是对象则为配置，否则取第三个参数
    const options = typeof context === 'object' ? context : optionalParams[0] || {};
    const level = options.level || 'info';

    if(options.logger === "file"){
      this.fileLogger.log(level, message);
    }else{
      this.consoleLogger.log(level, message);
    }
  }

  error(message: any, trace?: string, context?: string, ...optionalParams: any[]) {
    const options = typeof context === 'object' ? context : optionalParams[0] || {};
    const level = options.level || 'error';

    if(options.logger === "file"){
      this.fileLogger.error(level, message, trace);
    }else{
      this.consoleLogger.error(level, message, trace);
    }
  }

  // 补全LoggerService要求的剩余方法
  warn(message: any, context?: string, ...optionalParams: any[]) {
    const options = typeof context === 'object' ? context : optionalParams[0] || {};
    const level = options.level || 'warn';
    if(options.logger === "file"){
      this.fileLogger.warn(level, message);
    }else{
      this.consoleLogger.warn(level, message);
    }
  }

  debug(message: any, context?: string, ...optionalParams: any[]) {
    const options = typeof context === 'object' ? context : optionalParams[0] || {};
    const level = options.level || 'debug';
    if(options.logger === "file"){
      this.fileLogger.debug(level, message);
    }else{
      this.consoleLogger.debug(level, message);
    }
  }

  verbose(message: any, context?: string, ...optionalParams: any[]) {
    const options = typeof context === 'object' ? context : optionalParams[0] || {};
    const level = options.level || 'verbose';
    if(options.logger === "file"){
      this.fileLogger.verbose(level, message);
    }else{
      this.consoleLogger.verbose(level, message);
    }
  }
}

2. 注册CustomLogger #

在对应业务模块中注册服务，跨模块使用需要导出：

import { Module } from '@nestjs/common';
import { CustomLogger } from './custom-logger.service';
import { TestingService } from './testing.service';

@Module({
  providers: [CustomLogger, TestingService],
  exports: [CustomLogger]
})
export class LoggerModule {}

如果要替换Nest全局日志服务，在main.ts中配置：

import { NestFactory } from '@nestjs/core';
import { AppModule } from './app.module';
import { CustomLogger } from './custom-logger.service';

async function bootstrap() {
  const app = await NestFactory.create(AppModule, {
    logger: new CustomLogger()
  });
  await app.listen(3000);
}
bootstrap();

3. 调用逻辑 #

原有调用方式无需修改即可正常运行，指定logger: "file"的日志仅写入文件，未指定的默认输出到控制台：

@Injectable()
export class TestingService {
  constructor(
    private logger: CustomLogger
  ) { }

  async createLog(message: string, level: string): Promise<void> {
   this.logger.log(message, { logger: "file", level });
  }
}

内容的提问来源于stack exchange，提问作者Muhammad Zeeshan