Added logging

vendor/github.com/op/go-logging/logger.go

@@ -0,0 +1,249 @@
+// Copyright 2013, Örjan Persson. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package logging implements a logging infrastructure for Go. It supports
+// different logging backends like syslog, file and memory. Multiple backends
+// can be utilized with different log levels per backend and logger.
+package logging
+
+import (
+	"bytes"
+	"fmt"
+	"log"
+	"os"
+	"strings"
+	"sync/atomic"
+	"time"
+)
+
+// Redactor is an interface for types that may contain sensitive information
+// (like passwords), which shouldn't be printed to the log. The idea was found
+// in relog as part of the vitness project.
+type Redactor interface {
+	Redacted() interface{}
+}
+
+// Redact returns a string of * having the same length as s.
+func Redact(s string) string {
+	return strings.Repeat("*", len(s))
+}
+
+var (
+	// Sequence number is incremented and utilized for all log records created.
+	sequenceNo uint64
+
+	// timeNow is a customizable for testing purposes.
+	timeNow = time.Now
+)
+
+// Record represents a log record and contains the timestamp when the record
+// was created, an increasing id, filename and line and finally the actual
+// formatted log line.
+type Record struct {
+	Id     uint64
+	Time   time.Time
+	Module string
+	Level  Level
+	Args   []interface{}
+
+	// message is kept as a pointer to have shallow copies update this once
+	// needed.
+	message   *string
+	fmt       string
+	formatter Formatter
+	formatted string
+}
+
+// Formatted returns the formatted log record string.
+func (r *Record) Formatted(calldepth int) string {
+	if r.formatted == "" {
+		var buf bytes.Buffer
+		r.formatter.Format(calldepth+1, r, &buf)
+		r.formatted = buf.String()
+	}
+	return r.formatted
+}
+
+// Message returns the log record message.
+func (r *Record) Message() string {
+	if r.message == nil {
+		// Redact the arguments that implements the Redactor interface
+		for i, arg := range r.Args {
+			if redactor, ok := arg.(Redactor); ok == true {
+				r.Args[i] = redactor.Redacted()
+			}
+		}
+		msg := fmt.Sprintf(r.fmt, r.Args...)
+		r.message = &msg
+	}
+	return *r.message
+}
+
+// Logger is the actual logger which creates log records based on the functions
+// called and passes them to the underlying logging backend.
+type Logger struct {
+	Module      string
+	backend     LeveledBackend
+	haveBackend bool
+
+	// ExtraCallDepth can be used to add additional call depth when getting the
+	// calling function. This is normally used when wrapping a logger.
+	ExtraCalldepth int
+}
+
+// SetBackend overrides any previously defined backend for this logger.
+func (l *Logger) SetBackend(backend LeveledBackend) {
+	l.backend = backend
+	l.haveBackend = true
+}
+
+// TODO call NewLogger and remove MustGetLogger?
+
+// GetLogger creates and returns a Logger object based on the module name.
+func GetLogger(module string) (*Logger, error) {
+	return &Logger{Module: module}, nil
+}
+
+// MustGetLogger is like GetLogger but panics if the logger can't be created.
+// It simplifies safe initialization of a global logger for eg. a package.
+func MustGetLogger(module string) *Logger {
+	logger, err := GetLogger(module)
+	if err != nil {
+		panic("logger: " + module + ": " + err.Error())
+	}
+	return logger
+}
+
+// Reset restores the internal state of the logging library.
+func Reset() {
+	// TODO make a global Init() method to be less magic? or make it such that
+	// if there's no backends at all configured, we could use some tricks to
+	// automatically setup backends based if we have a TTY or not.
+	sequenceNo = 0
+	b := SetBackend(NewLogBackend(os.Stderr, "", log.LstdFlags))
+	b.SetLevel(DEBUG, "")
+	SetFormatter(DefaultFormatter)
+	timeNow = time.Now
+}
+
+// IsEnabledFor returns true if the logger is enabled for the given level.
+func (l *Logger) IsEnabledFor(level Level) bool {
+	return defaultBackend.IsEnabledFor(level, l.Module)
+}
+
+func (l *Logger) log(lvl Level, format string, args ...interface{}) {
+	if !l.IsEnabledFor(lvl) {
+		return
+	}
+
+	// Create the logging record and pass it in to the backend
+	record := &Record{
+		Id:     atomic.AddUint64(&sequenceNo, 1),
+		Time:   timeNow(),
+		Module: l.Module,
+		Level:  lvl,
+		fmt:    format,
+		Args:   args,
+	}
+
+	// TODO use channels to fan out the records to all backends?
+	// TODO in case of errors, do something (tricky)
+
+	// calldepth=2 brings the stack up to the caller of the level
+	// methods, Info(), Fatal(), etc.
+	// ExtraCallDepth allows this to be extended further up the stack in case we
+	// are wrapping these methods, eg. to expose them package level
+	if l.haveBackend {
+		l.backend.Log(lvl, 2+l.ExtraCalldepth, record)
+		return
+	}
+
+	defaultBackend.Log(lvl, 2+l.ExtraCalldepth, record)
+}
+
+// Fatal is equivalent to l.Critical(fmt.Sprint()) followed by a call to os.Exit(1).
+func (l *Logger) Fatal(args ...interface{}) {
+	s := fmt.Sprint(args...)
+	l.log(CRITICAL, "%s", s)
+	os.Exit(1)
+}
+
+// Fatalf is equivalent to l.Critical followed by a call to os.Exit(1).
+func (l *Logger) Fatalf(format string, args ...interface{}) {
+	l.log(CRITICAL, format, args...)
+	os.Exit(1)
+}
+
+// Panic is equivalent to l.Critical(fmt.Sprint()) followed by a call to panic().
+func (l *Logger) Panic(args ...interface{}) {
+	s := fmt.Sprint(args...)
+	l.log(CRITICAL, "%s", s)
+	panic(s)
+}
+
+// Panicf is equivalent to l.Critical followed by a call to panic().
+func (l *Logger) Panicf(format string, args ...interface{}) {
+	s := fmt.Sprintf(format, args...)
+	l.log(CRITICAL, "%s", s)
+	panic(s)
+}
+
+// Critical logs a message using CRITICAL as log level.
+func (l *Logger) Critical(format string, args ...interface{}) {
+	l.log(CRITICAL, format, args...)
+}
+
+// Error logs a message using ERROR as log level.
+func (l *Logger) Error(format string, args ...interface{}) {
+	l.log(ERROR, format, args...)
+}
+
+// Errorf logs a message using ERROR as log level.
+func (l *Logger) Errorf(format string, args ...interface{}) {
+	l.log(ERROR, format, args...)
+}
+
+// Warning logs a message using WARNING as log level.
+func (l *Logger) Warning(format string, args ...interface{}) {
+	l.log(WARNING, format, args...)
+}
+
+// Warningf logs a message using WARNING as log level.
+func (l *Logger) Warningf(format string, args ...interface{}) {
+	l.log(WARNING, format, args...)
+}
+
+// Notice logs a message using NOTICE as log level.
+func (l *Logger) Notice(format string, args ...interface{}) {
+	l.log(NOTICE, format, args...)
+}
+
+// Noticef logs a message using NOTICE as log level.
+func (l *Logger) Noticef(format string, args ...interface{}) {
+	l.log(NOTICE, format, args...)
+}
+
+// Info logs a message using INFO as log level.
+func (l *Logger) Info(format string, args ...interface{}) {
+	l.log(INFO, format, args...)
+}
+
+// Infof logs a message using INFO as log level.
+func (l *Logger) Infof(format string, args ...interface{}) {
+	l.log(INFO, format, args...)
+}
+
+// Debug logs a message using DEBUG as log level.
+func (l *Logger) Debug(format string, args ...interface{}) {
+	l.log(DEBUG, format, args...)
+}
+
+// Debugf logs a message using DEBUG as log level.
+func (l *Logger) Debugf(format string, args ...interface{}) {
+	l.log(DEBUG, format, args...)
+}
+
+func init() {
+	Reset()
+}