Local Filesystem Hook for Logrus

Sometimes developers like to write directly to a file on the filesystem. This is a hook for logrus designed to allow users to do just that. The log levels are dynamic at instanciation of the hook, so it is capable of logging at some or all levels.

Example

import (
	log "github.com/sirupsen/logrus"
	"github.com/rifflock/lfshook"
)

var Log *log.Logger

func NewLogger( config map[string]interface{} ) *log.Logger {
	if Log != nil {
		return Log
	}

	Log = log.New()
	Log.Formatter = new(log.JSONFormatter)
	Log.Hooks.Add(lfshook.NewHook(lfshook.PathMap{
		log.InfoLevel : "/var/log/info.log",
		log.ErrorLevel : "/var/log/error.log",
	}))
	return Log
}

Formatters

lfshook will strip colors from any TextFormatter type formatters when writing to local file, because the color codes don't look so great.

Log rotation

In order to enable automatic log rotation it's possible to provide an io.Writer instead of the path string of a log file. In combination with pakages like go-file-rotatelogs log rotation can easily be achieved.

  import "github.com/lestrrat/go-file-rotatelogs"

  path := "/var/log/go.log"
  writer := rotatelogs.NewRotateLogs(
    path + ".%Y%m%d%H%M",
    rotatelogs.WithLinkName(path),
    rotatelogs.WithMaxAge(time.Duration(86400) * time.Second),
    rotatelogs.WithRotationTime(time.Duration(604800) * time.Second),
  )

  log.Hooks.Add(lfshook.NewHook(lfshook.WriterMap{
    logrus.InfoLevel: writer,
    logrus.ErrorLevel: writer,
  }))

Note:

Whichever user is running the go application must have read/write permissions to the log files selected, or if the files do not yet exists, then to the directory in which the files will be created.