minio/cmd/logger-file-hook.go

/*
 * Minio Cloud Storage, (C) 2015, 2016 Minio, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package cmd

import (
	"fmt"
	"io/ioutil"
	"os"

	"github.com/Sirupsen/logrus"
)

type fileLogger struct {
	Enable   bool   `json:"enable"`
	Filename string `json:"fileName"`
	Level    string `json:"level"`
}

type localFile struct {
	*os.File
}

func enableFileLogger() {
	flogger := serverConfig.GetFileLogger()
	if !flogger.Enable || flogger.Filename == "" {
		return
	}

	// Creates the named file with mode 0666, honors system umask.
	file, err := os.OpenFile(flogger.Filename, os.O_CREATE|os.O_APPEND|os.O_WRONLY, 0666)
	fatalIf(err, "Unable to open log file.")

	fileLogger := logrus.New()

	// Add a local file hook.
	fileLogger.Hooks.Add(&localFile{file})

	lvl, err := logrus.ParseLevel(flogger.Level)
	fatalIf(err, "Unknown log level found in the config file.")

	// Set default JSON formatter.
	fileLogger.Out = ioutil.Discard
	fileLogger.Formatter = new(logrus.JSONFormatter)
	fileLogger.Level = lvl // Minimum log level.

	log.mu.Lock()
	log.loggers = append(log.loggers, fileLogger)
	log.mu.Unlock()
}

// Fire fires the file logger hook and logs to the file.
func (l *localFile) Fire(entry *logrus.Entry) error {
	line, err := entry.String()
	if err != nil {
		return fmt.Errorf("Unable to read entry, %v", err)
	}
	l.File.Write([]byte(line))
	l.File.Sync()
	return nil
}

// Levels - indicate log levels supported.
func (l *localFile) Levels() []logrus.Level {
	return []logrus.Level{
		logrus.PanicLevel,
		logrus.FatalLevel,
		logrus.ErrorLevel,
	}
}