pkg/logger/logger.go

// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
//
// 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 logger

import (
	"os"
	"strings"

	"go.uber.org/zap"
	"go.uber.org/zap/zapcore"
	lumberjack "gopkg.in/natefinch/lumberjack.v2"
)

// Configuration stores the config for the logger
type Configuration struct {
	LogLevel    string
	LogLocation string
}

// getZapLevel converts log level string to zapcore.Level
func getZapLevel(inputLogLevel string) zapcore.Level {
	lvl := strings.ToLower(inputLogLevel)

	switch lvl {
	case "debug":
		return zapcore.DebugLevel
	case "info":
		return zapcore.InfoLevel
	case "warn":
		return zapcore.WarnLevel
	case "error":
		return zapcore.ErrorLevel
	case "fatal":
		return zapcore.FatalLevel
	default:
		return zapcore.DebugLevel
	}
}

func getEncoder() zapcore.Encoder {
	encoderConfig := zap.NewProductionEncoderConfig()
	encoderConfig.EncodeTime = zapcore.ISO8601TimeEncoder
	return zapcore.NewJSONEncoder(encoderConfig)
}

func (logConfig *Configuration) newZapLogger() *zap.Logger { //Logger {
	var cores []zapcore.Core

	logLevel := getZapLevel(logConfig.LogLevel)

	writer := getLogFilePath(logConfig.LogLocation)

	cores = append(cores, zapcore.NewCore(getEncoder(), writer, logLevel))

	combinedCore := zapcore.NewTee(cores...)

	logger := zap.New(combinedCore,
		zap.AddCaller(),
	)
	defer logger.Sync()

	return logger
}

// getLogFilePath returns the writer
func getLogFilePath(logFilePath string) zapcore.WriteSyncer {
	var writer zapcore.WriteSyncer

	if logFilePath == "" {
		writer = zapcore.Lock(os.Stderr)
	} else if strings.ToLower(logFilePath) != "stdout" {
		writer = getLogWriter(logFilePath)
	} else {
		writer = zapcore.Lock(os.Stdout)
	}

	return writer
}

// getLogWriter is for lumberjack
func getLogWriter(logFilePath string) zapcore.WriteSyncer {
	lumberJackLogger := &lumberjack.Logger{
		Filename:   logFilePath,
		MaxSize:    100,
		MaxBackups: 5,
		MaxAge:     30,
		Compress:   true,
	}
	return zapcore.AddSync(lumberJackLogger)
}

// New logger initializes logger
func New(logLevel, logLocation string) *zap.Logger {
	inputLogConfig := &Configuration{
		LogLevel:    logLevel,
		LogLocation: logLocation,
	}

	logger := inputLogConfig.newZapLogger()
	return logger
}