Node.js+Express.js+log4js

※「≈≈≈」は省略を表す

バージョン

$ node -v
v6.2.1

$ cat package.json
{
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  "dependencies": {
    "express": "~4.13.1",
    "log4js": "^0.6.37",
    ≈≈≈
  },
  ≈≈≈
}

log4jsの設定

$ mkdir modules
$ cat modules/logger.js 
var log4js = require('log4js');

log4js.configure({
    "appenders": [{
      "category": "access",
      "type": "dateFile",
      "filename": "/var/log/nodejs/access.log",
      "pattern": "-yyyy-MM-dd",
      "backups": 3
    },
    {
      "category": "system",
      "type": "dateFile",
      "filename": "/var/log/nodejs/system.log",
      "pattern": "-yyyy-MM-dd",
      "backups": 3
    },
    {
      "category": "error",
      "type": "dateFile",
      "filename": "/var/log/nodejs/error.log",
      "pattern": "-yyyy-MM-dd",
      "backups": 3
    },
    {
      "type": "console"
    }],
    "levels": {
      "access": "ALL",
      "system": "ALL",
      "error": "ERROR"
    }
});

module.exports = { 
  access: log4js.getLogger('access'),
  system: log4js.getLogger('system'),
  error: log4js.getLogger('error'),
  express: log4js.connectLogger(log4js.getLogger('access'), {level: log4js.levels.INFO}),
  isDebug: function(category) {
    return (log4js.levels.DEBUG.level >= category.level.level);
  }
};

app.js

$ cat app.js
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var logger = require('./modules/logger');
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app.use(logger.express);
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使い方

$ cat app.js
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var test = require('../routes/test');
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app.use('/', test);
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$ cat routes/test.js
var express = require('express');
var logger  = require('../modules/logger');
var router = express.Router();

router.get('/', function(req, res, next) {
  if(logger.isDebug(logger.system)) {
    logger.system.debug("debugログは、DEBUGレベルの時だけ呼びたい。");
  }

  logger.error.error("errorじゃないけどね！");
}

module.exports = router;