【Backend入門】Express.js+Typescriptでのウェブサーバ(logging)

概要

ログを出しかた、log4jsを利用しての方法について記述したいと思います。

log4jsとは

javaで利用されているlog4jをjavascriptで利用できるようにしたモジュール。

導入

モジュールのインストールします。

$ npm install log4js
$ npm install -D @types/log4js

configを設定します。

{
  "appenders": {
    "console": { "type": "console" },
    "file": { "type": "file", "filename": "logs/server.log" }
  },
  "categories": {
    "default": { "appenders": ["console", "file"], "level": "debug" }
  }
}

使用の用意します。

import log4js from 'log4js';
...
const logConfigure: log4js.Configuration = {
  "appenders": {
    "console": { "type": "console" },
    "file": { "type": "file", "filename": "logs/server.log" }
  },
  "categories": {
    "default": { "appenders": ["console", "file"], "level": "debug" }
  }
} 

const logger = log4js.configure(logConfigure).getLogger();
...

app.listen(port, () => {
  console.log(`Server is running on port: ${port}`);
  logger.log(`Server is running on port: ${port}`);
});

起動してログを確認する

$ npx ts-node src/index.ts
Server is running on port: 3000
[2024-04-01T16:06:33.450] [INFO] default - Server is running on port: 3000
..
..
$ cat logs/server.log
[2024-04-01T16:06:33.450] [INFO] default - Server is running on port: 3000

全体

index.ts

import cors, { CorsOptions } from 'cors';
import express from 'express';
import dotenv from 'dotenv';
import { router } from './router';
import log4js from 'log4js';

dotenv.config();

const app = express();
const port = process.env.PORT || 3000;

const logConfigure: log4js.Configuration = {
  "appenders": {
    "console": { "type": "console" },
    "file": { "type": "file", "filename": "logs/server.log" }
  },
  "categories": {
    "default": { "appenders": ["console", "file"], "level": "debug" }
  }
} 

const logger = log4js.configure(logConfigure).getLogger();

const corsOptions: CorsOptions = {
  origin: ['http://localhost:3000'],
  methods: [ 'GET', 'POST', 'PUT', 'DELET' ],
  allowedHeaders: [ 'Content-Type', 'X-Requested-With',  'Authorization' ],
}

app.use(cors(corsOptions));

// ミドルウェア設定
app.use(express.json());

// 
app.use('/users',router);

app.listen(port, () => {
  console.log(`Server is running on port: ${port}`);
  logger.log(`Server is running on port: ${port}`);
});

configをファイル化して構造的にする

$ cat config/log.config.json
{
  "appenders": {
    "console": { "type": "console" },
    "file": { "type": "file", "filename": "logs/server.log" }
  },
  "categories": {
    "default": { "appenders": ["console", "file"], "level": "debug" }
  }
} 

index.tsの変更

import cors, { CorsOptions } from 'cors';
import express from 'express';
import dotenv from 'dotenv';
import { router } from './router';
import log4js from 'log4js';

dotenv.config();

const app = express();
const port = process.env.PORT || 3000;

const logger = log4js.configure('src/config/log.config.json').getLogger();

const corsOptions: CorsOptions = {
  origin: ['http://localhost:3000'],
  methods: [ 'GET', 'POST', 'PUT', 'DELET' ],
  allowedHeaders: [ 'Content-Type', 'X-Requested-With',  'Authorization' ],
}

app.use(cors(corsOptions));

// ミドルウェア設定
app.use(express.json());

// 
app.use('/users',router);

app.listen(port, () => {
  console.log(`Server is running on port: ${port}`);
  logger.log(`Server is running on port: ${port}`);
});