Use the nodeJs koa2 framework to develop back-end applications, and use the koa-log4 middleware to manage the access logs and system logs of nodeJs.

I. installation of koa-log4

Because the project uses koa2, the higher version of log4 is installed,

$ npm i --save koa-log4@2

If using koa1, use the directive

$ npm i --save koa-log4@1

koa-log4 Npm Homepage

2. Create a new log4.js file to configure log4

const path = require('path');//Introducing native path module
const log4js = require('koa-log4');//Introducing koa-log4

log4js.configure({
  appenders: {
    //Access log
    access: {
      type: 'dateFile',
      pattern: '-yyyy-MM-dd.log', //Generate files by date
      alwaysIncludePattern: true, //Filenames are always distinguished by date
      encoding:"utf-8",
      filename: path.join('logs/', 'access.log') //Build file path and file name
    },
    //system log
    application: {
      type: 'dateFile',
      pattern: '-yyyy-MM-dd.log', //Generate files by date
      alwaysIncludePattern: true, //Filenames are always distinguished by date
      encoding:"utf-8",
      filename: path.join('logs/', 'application.log') //Build file path and file name
    },
    out: {
      type: 'console'
    }
  },
  categories: {
    default: { appenders: [ 'out' ], level: 'info' },
    access: { appenders: [ 'access' ], level: 'info' },
    application: { appenders: [ 'application' ], level: 'WARN'}
  }
});

exports.accessLogger = () => log4js.koaLogger(log4js.getLogger('access')); //Log all access levels
exports.logger = log4js.getLogger('application');  //Log all application levels

III. if log is used

• Access log -- record all access requests of users, and use it in the form of Middleware in the koa portal

    const Koa = require('koa');
    const app = new Koa();
    const {  accessLogger,systemLogger, } = require('./logger');
    const router = new KoaRouter();
    app.use(accessLogger()); //middleware

• System log -- error recording system status

     app.on('error', err => {logger.error(err); });
  

Four, effect