安装 (terminal)

npm install log4js

logger.js 简易内容

var log4js = require('log4js');
log4js.configure( options ) ;
var logger = log4js.getLogger([category]);
module.exports = logger;

logger.js 具体内容梳理

const log4js = require( "log4js" );
const options = {
    appenders: {
        out: {
            type: "stdout",
            layout: {
                type: "pattern",
                pattern: "%[[%x{reqid}] [%d{ISO8601_WITH_TZ_OFFSET}] [%x{ip}] [%p] [%x{user}]%] %m%n",
                tokens: {
                    user( logEvent ) {
                        if ( logEvent.context.user ) {
                            return logEvent.context.user;
                        }
                        return "";
                    }
                }
            }
        },
        file: {
            type: "file",
            filename: "logs/access.log",
            maxLogSize: 10485760,
            layout: {
                type: "messagePassThrough"
            },
            compress: true
        }
    },
    categories: {
        "out": {
            appenders: [ "out" ],
            level: "info"
        },
        default: {
            appenders: [ "file" ],
            level: "info"
        }
    }
} 
log4js.configure( options );

var logger = log4js.getLogger( "out" );

module.exports = logger;

options 配置

options:

1. levels:
   All -> Trace -> Debug -> Info -> Warn -> Error -> Fatal -> Mark -> Off(关闭)
2. appenders ( appendersObject ):
   日志事件序列化为某种形式的输出
3. categories ( categoriesObject ):
   用于分组日志事件的标签
4. pm2, pm2InstanceVar, disableClustering:
   与PM2相关的配置

appendersObject { key : object}
key: {
type: types, (required)
layout: layoutObject
}

types : 输出类型

• categoryFilter
• console (向控制台写入大量输出会使应用程序占用大量内存。如果遇到此问题，请尝试切换到stdout appender。
  )
• dateFile (filename, pattern('.yyyy-MM-dd-hh'), compress, encoding)
• file (filename, maxLogSize, backups, compress, encoding)
• fileSync ( 不支持compress)
• logLevelFilter
• multiFile (多文件 ,base, extension(后缀), timeout, property: 'categoryName' (用于文件名区分))
• multiprocess (多进程 mode(master | worker), appender(针对master), loggerPort, loggerHost )
• recording
• stderr (标准错误流)
• stdout (标准输出流)
• tcp (port, host)
• tcp-server

layoutObject: 输出格式 【也可自定义layout】

• basic: 时间，级别， 类别， 信息
  [2017-03-30 07:57:00.113] [ERROR] cheese - Cheese is too ripe!
• colored: 比 basic 多了颜色
  TRACE - '蓝色blue' | DEBUG - '青色cyan' | INFO - '绿色green' | WARN - '黄色yellow' | ERROR - '红red' | FATAL - '洋红色magenta'
• pattern (pattern(patternString), tokens(tokenObject))

patternString

• %r time in toLocaleTimeString format
• %p 日志级别
• %c 日志种类
• %h 主机名
• %m 日志信息
• %d 日志日期 (默认2017-06-01 08:32:56.283) %d{yyyy/MM/dd-hh.mm.ss}
• %% % - for when you want a literal % in your output
• %n 换行
• %z process id (from process.pid)
• %x{<tokenname>} 将tokens中的变量带入
• %X{<tokenname>} logger.addContext('user', 'charlie'); 将user带入
• %[ start a coloured block (colour will be taken from the log level, similar to colouredLayout)
• %] end a coloured block

tokenObject

tokens: {
  reqid( logEvent ) {
  if ( logEvent.context.reqid ) {
    return logEvent.context.reqid;
  }
  return "";
}

categoriesObject : 必有一个default
"out" : {
appenders: [ "out" ],
level: "info"
},
default: {
appenders: [ "file" ],
level: "info"
}

自定义layout

log4js.addLayout('json', function(config) {
  return function(logEvent) { return JSON.stringify(logEvent); }
});

LogEvent 对象

LoggingEvent {
  startTime: 2018-12-03T05:57:50.033Z,
  categoryName: '[Logger]',
  data: [ '拉取日志失败' ],
  level: Level { level: 40000, levelStr: 'ERROR', colour: 'red' },
  context: {},
  pid: 2262 } {}
}