Justlog NPM | npm.io

justlog

justlog , focus on logging

Features:

coloured console logging
file appender, with log rotate based on time
configurable log message/patterns
different log levels for different log categories (info debug warn error )
can use as a connect middleware for access-log

Installation

npm install justlog

Usage

Getting start

// simple.js
var justlog = require('justlog');

var log = justlog(); 
l.info('simple', 'info');
l.debug({a:1, b:2});
l.warn([1,2,3,4]);
l.error('name:%s, number:%d', 'somename', 123);

$ node simple.js

the stdout/stderr is as below

19:01:41 INFO  a.js:4 simple info
19:01:41 DEBUG a.js:5 {"a":1,"b":2}
19:01:41 WARN  a.js:6 1,2,3,4
19:01:41 ERROR a.js:7 name:somename, number:123

and also, you can got a log file on logs/simple-%Y-%M-%D.log

2013-01-06 19:01:41 [WARN] (a.js:6) 1,2,3,4
2013-01-06 19:01:41 [ERROR] (a.js:7) name:somename, number:123

Change log levels

var log = justlog({
  file : {level: justlog.INFO | justlog.WARN} // file log levels
  stdio : {level: justlog.DEBUG | justlog.ERROR} // stdio log levels
});

available levels

justlog.INFO
justlog.DEBUG
justlog.WARN
justlog.ERROR
justlog.ALL include all 4 level above
justlog.EXCEPTION include WARN and ERROR

Log only one way

var stdLog = justlog({file : false}); // not write log file, only use stdio
var fileLog = justlog({stdio : false}); // not use stdio, only write a log file
});

log error & warn messages into stdout

var log = justlog({
  stdio: {
    stderr: process.stdout
  }
});

custom log file path & log file rotate

// write logs into filename.log and never rotate
var log1 = justlog({
  file: {
    path : '[filename.log]'
  }
});

// write logs into filename-%Y-%M-%D.log, and rotate every days
var log2 = justlog({
  file: {
    path : '[filename]-YYYY-MM-DD[.log]'
  }
});

time format use moment string-format

rotate will be trigger when log filename changed.

custom log line format

var log = justlog({
  file : {
    pattern : '{fulltime} [{level}] {msg}' // use custom pattern
  }
  stdio : {
    pattern : 'simple-color' // use predefined pattern
  }
});
log.warn('log msg');

All options

{
  file : {
    level           : error | warn, // levels for filelog
    pattern         : 'file', // filelog pattern
    path            : '[logs/%main_script_name]YYYY-MM-DD[.log]', // log file path
    mode            : '0664', // log file mode
    dir_mode        : '2775', // if log dir is not exists, log dir mode when create
    _watcher_timeout : 5007,  // log file renamed watch timeout, DO NOT CHANGE THIS IF YOU REALLY KNOWN WHAT YOU DO.
  },
  stdio : {
    level   : error | warn | debug | info, // levels for stdio
    pattern : 'color', // stdio pattern
    stdout  : process.stdout, // stdout stream (for info & debug log)
    stderr  : process.stderr, // stderr stream (for warn & error log)
  }
}

Middleware

a connect middleware for apache-like accesslog.

middleware's has same options as normally justlog object, but has different default value

var app = connect();
app.use(justlog.middleware({}));

Middleware default options

{
  file: {
    path    : '[logs/%main_script_name-access-]YYYY-MM-DD[.log]',
    pattern : 'accesslog-rt'
  }
  stdio :
    pattern : 'accesslog-color'
}

Buffer Log

you can buffer your log if you have big visits.

var log = justlog({
  duration : 1000, // flush buffer time, default is 1000
  bufferLength : 1000 // max buffer length, default is 0
  //... other options
});

var log = justlog.create({
  duration : 1000, // flush buffer time, default is 1000
  bufferLength : 1000 // max buffer length, default is 0
});

default options

{
  duration : 1000,
  bufferLength : 0,
  // file: ...
  // stdio : ...
}

close buffer log

justlog.end(cb);

About log pattern

Justlog has a powerful log line pattern support. You can use variables, objects and functions in you patterns. And you can define ansi color output patterns easily.

Syntax

{var[ args...][@colors...]}

"{variable_name}": show varaible's value. eg. {remote-address}
"{object_name.prop_name}": show property value. eg. {headers.accepted-encoding}
"{function_name "const1", "const2"}": show function's return value with const arguments. eg. {now "YYYY-MM-DD"}
"{function_name variable_name, object_name.prop_name}": show function's return value with variable arguments. eg. {color.status status-code}
"{something@color1,color2}": set output ansi color. eg. {url@blue,underline}