Break out logger as a reusable component

2014-10-26 13:16:54 +01:00
parent 58945a429f
commit 15ee9a5cac
19 changed files with 74 additions and 42 deletions
@@ -0,0 +1,160 @@
+// Copyright (C) 2014 Jakob Borg. All rights reserved. Use of this source code
+// is governed by an MIT-style license that can be found in the LICENSE file.
+
+// Package logger implements a standardized logger with callback functionality
+package logger
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"strings"
+	"sync"
+)
+
+type LogLevel int
+
+const (
+	LevelDebug LogLevel = iota
+	LevelInfo
+	LevelOK
+	LevelWarn
+	LevelFatal
+	NumLevels
+)
+
+// A MessageHandler is called with the log level and message text.
+type MessageHandler func(l LogLevel, msg string)
+
+type Logger struct {
+	logger   *log.Logger
+	handlers [NumLevels][]MessageHandler
+	mut      sync.Mutex
+}
+
+// The default logger logs to standard output with a time prefix.
+var DefaultLogger = New()
+
+func New() *Logger {
+	return &Logger{
+		logger: log.New(os.Stdout, "", log.Ltime),
+	}
+}
+
+// AddHandler registers a new MessageHandler to receive messages with the
+// specified log level or above.
+func (l *Logger) AddHandler(level LogLevel, h MessageHandler) {
+	l.mut.Lock()
+	defer l.mut.Unlock()
+	l.handlers[level] = append(l.handlers[level], h)
+}
+
+// See log.SetFlags
+func (l *Logger) SetFlags(flag int) {
+	l.logger.SetFlags(flag)
+}
+
+// See log.SetPrefix
+func (l *Logger) SetPrefix(prefix string) {
+	l.logger.SetPrefix(prefix)
+}
+
+func (l *Logger) callHandlers(level LogLevel, s string) {
+	for _, h := range l.handlers[level] {
+		h(level, strings.TrimSpace(s))
+	}
+}
+
+// Debugln logs a line with a DEBUG prefix.
+func (l *Logger) Debugln(vals ...interface{}) {
+	l.mut.Lock()
+	defer l.mut.Unlock()
+	s := fmt.Sprintln(vals...)
+	l.logger.Output(2, "DEBUG: "+s)
+	l.callHandlers(LevelDebug, s)
+}
+
+// Debugf logs a formatted line with a DEBUG prefix.
+func (l *Logger) Debugf(format string, vals ...interface{}) {
+	l.mut.Lock()
+	defer l.mut.Unlock()
+	s := fmt.Sprintf(format, vals...)
+	l.logger.Output(2, "DEBUG: "+s)
+	l.callHandlers(LevelDebug, s)
+}
+
+// Infoln logs a line with an INFO prefix.
+func (l *Logger) Infoln(vals ...interface{}) {
+	l.mut.Lock()
+	defer l.mut.Unlock()
+	s := fmt.Sprintln(vals...)
+	l.logger.Output(2, "INFO: "+s)
+	l.callHandlers(LevelInfo, s)
+}
+
+// Infof logs a formatted line with an INFO prefix.
+func (l *Logger) Infof(format string, vals ...interface{}) {
+	l.mut.Lock()
+	defer l.mut.Unlock()
+	s := fmt.Sprintf(format, vals...)
+	l.logger.Output(2, "INFO: "+s)
+	l.callHandlers(LevelInfo, s)
+}
+
+// Okln logs a line with an OK prefix.
+func (l *Logger) Okln(vals ...interface{}) {
+	l.mut.Lock()
+	defer l.mut.Unlock()
+	s := fmt.Sprintln(vals...)
+	l.logger.Output(2, "OK: "+s)
+	l.callHandlers(LevelOK, s)
+}
+
+// Okf logs a formatted line with an OK prefix.
+func (l *Logger) Okf(format string, vals ...interface{}) {
+	l.mut.Lock()
+	defer l.mut.Unlock()
+	s := fmt.Sprintf(format, vals...)
+	l.logger.Output(2, "OK: "+s)
+	l.callHandlers(LevelOK, s)
+}
+
+// Warnln logs a formatted line with a WARNING prefix.
+func (l *Logger) Warnln(vals ...interface{}) {
+	l.mut.Lock()
+	defer l.mut.Unlock()
+	s := fmt.Sprintln(vals...)
+	l.logger.Output(2, "WARNING: "+s)
+	l.callHandlers(LevelWarn, s)
+}
+
+// Warnf logs a formatted line with a WARNING prefix.
+func (l *Logger) Warnf(format string, vals ...interface{}) {
+	l.mut.Lock()
+	defer l.mut.Unlock()
+	s := fmt.Sprintf(format, vals...)
+	l.logger.Output(2, "WARNING: "+s)
+	l.callHandlers(LevelWarn, s)
+}
+
+// Fatalln logs a line with a FATAL prefix and exits the process with exit
+// code 1.
+func (l *Logger) Fatalln(vals ...interface{}) {
+	l.mut.Lock()
+	defer l.mut.Unlock()
+	s := fmt.Sprintln(vals...)
+	l.logger.Output(2, "FATAL: "+s)
+	l.callHandlers(LevelFatal, s)
+	os.Exit(1)
+}
+
+// Fatalf logs a formatted line with a FATAL prefix and exits the process with
+// exit code 1.
+func (l *Logger) Fatalf(format string, vals ...interface{}) {
+	l.mut.Lock()
+	defer l.mut.Unlock()
+	s := fmt.Sprintf(format, vals...)
+	l.logger.Output(2, "FATAL: "+s)
+	l.callHandlers(LevelFatal, s)
+	os.Exit(1)
+}