git » log » commit c82a0ea

diff --git a/log.go b/log.go
new file mode 100644
index 0000000..9cde2d1
--- /dev/null
+++ b/log.go
@@ -0,0 +1,249 @@
+// Package log implements a simple logger.
+//
+// It implements an API somewhat similar to "github.com/google/glog" with a
+// focus towards logging to stderr, which is useful for systemd-based
+// environments.
+//
+// There are command line flags (defined using the flag package) to control
+// the behaviour of the default logger. By default, it will write to stderr
+// without timestamps; this is suitable for systemd (or equivalent) logging.
+package log
+
+import (
+	"flag"
+	"fmt"
+	"io"
+	"log/syslog"
+	"os"
+	"path/filepath"
+	"runtime"
+	"strconv"
+	"strings"
+	"sync"
+	"time"
+)
+
+// Flags that control the default logging.
+var (
+	vLevel = flag.Int("v", 0, "Verbosity level (1 = debug)")
+
+	logFile = flag.String("logfile", "",
+		"file to log to (enables logtime)")
+
+	logToSyslog = flag.String("logtosyslog", "",
+		"log to syslog, with the given tag")
+
+	logTime = flag.Bool("logtime", false,
+		"include the time when writing the log to stderr")
+
+	alsoLogToStderr = flag.Bool("alsologtostderr", false,
+		"also log to stderr, in addition to the file")
+)
+
+// Logging levels.
+type Level int
+
+const (
+	Error = Level(-1)
+	Info  = Level(0)
+	Debug = Level(1)
+)
+
+var levelToLetter = map[Level]string{
+	Error: "E",
+	Info:  "_",
+	Debug: ".",
+}
+
+// A Logger represents a logging object that writes logs to the given writer.
+type Logger struct {
+	Level   Level
+	LogTime bool
+
+	CallerSkip int
+
+	w io.WriteCloser
+	sync.Mutex
+}
+
+func New(w io.WriteCloser) *Logger {
+	return &Logger{
+		w:          w,
+		CallerSkip: 0,
+		Level:      Info,
+		LogTime:    true,
+	}
+}
+
+func NewFile(path string) (*Logger, error) {
+	f, err := os.OpenFile(path, os.O_CREATE|os.O_APPEND|os.O_WRONLY, 0644)
+	if err != nil {
+		return nil, err
+	}
+
+	l := New(f)
+	l.LogTime = true
+	return l, nil
+}
+
+func NewSyslog(priority syslog.Priority, tag string) (*Logger, error) {
+	w, err := syslog.New(priority, tag)
+	if err != nil {
+		return nil, err
+	}
+
+	l := New(w)
+	l.LogTime = false
+	return l, nil
+}
+
+func (l *Logger) Close() {
+	l.w.Close()
+}
+
+func (l *Logger) V(level Level) bool {
+	return level <= l.Level
+}
+
+func (l *Logger) Log(level Level, skip int, format string, a ...interface{}) {
+	if !l.V(level) {
+		return
+	}
+
+	// Message.
+	msg := fmt.Sprintf(format, a...)
+
+	// Caller.
+	_, file, line, ok := runtime.Caller(1 + l.CallerSkip + skip)
+	if !ok {
+		file = "unknown"
+	}
+	fl := fmt.Sprintf("%s:%-4d", filepath.Base(file), line)
+	if len(fl) > 18 {
+		fl = fl[len(fl)-18:]
+	}
+	msg = fmt.Sprintf("%-18s", fl) + " " + msg
+
+	// Level.
+	letter, ok := levelToLetter[level]
+	if !ok {
+		letter = strconv.Itoa(int(level))
+	}
+	msg = letter + " " + msg
+
+	// Time.
+	if l.LogTime {
+		msg = time.Now().Format("20060102 15:04:05.000000 ") + msg
+	}
+
+	if !strings.HasSuffix(msg, "\n") {
+		msg += "\n"
+	}
+
+	l.Lock()
+	l.w.Write([]byte(msg))
+	l.Unlock()
+}
+
+func (l *Logger) Debugf(format string, a ...interface{}) {
+	l.Log(Debug, 1, format, a...)
+}
+
+func (l *Logger) Infof(format string, a ...interface{}) {
+	l.Log(Info, 1, format, a...)
+}
+
+func (l *Logger) Errorf(format string, a ...interface{}) error {
+	l.Log(Error, 1, format, a...)
+	return fmt.Errorf(format, a...)
+}
+
+func (l *Logger) Fatalf(format string, a ...interface{}) {
+	l.Log(-2, 1, format, a...)
+	// TODO: Log traceback?
+	os.Exit(1)
+}
+
+// The default logger, used by the top-level functions below.
+var Default = &Logger{
+	w:          os.Stderr,
+	CallerSkip: 1,
+	Level:      Info,
+	LogTime:    false,
+}
+
+// Init the default logger, based on the command-line flags.
+// Must be called after flag.Parse().
+func Init() {
+	var err error
+
+	if *logToSyslog != "" {
+		Default, err = NewSyslog(syslog.LOG_DAEMON|syslog.LOG_INFO, *logToSyslog)
+		if err != nil {
+			panic(err)
+		}
+	} else if *logFile != "" {
+		Default, err = NewFile(*logFile)
+		if err != nil {
+			panic(err)
+		}
+		*logTime = true
+	}
+
+	if *alsoLogToStderr && Default.w != os.Stderr {
+		Default.w = multiWriteCloser(Default.w, os.Stderr)
+	}
+
+	Default.CallerSkip = 1
+	Default.Level = Level(*vLevel)
+	Default.LogTime = *logTime
+}
+
+func V(level Level) bool {
+	return Default.V(level)
+}
+
+func Log(level Level, skip int, format string, a ...interface{}) {
+	Default.Log(level, skip, format, a...)
+}
+
+func Debugf(format string, a ...interface{}) {
+	Default.Debugf(format, a...)
+}
+
+func Infof(format string, a ...interface{}) {
+	Default.Infof(format, a...)
+}
+
+func Errorf(format string, a ...interface{}) error {
+	return Default.Errorf(format, a...)
+}
+
+func Fatalf(format string, a ...interface{}) {
+	Default.Fatalf(format, a...)
+}
+
+// multiWriteCloser creates a WriteCloser that duplicates its writes and
+// closes to all the provided writers.
+func multiWriteCloser(wc ...io.WriteCloser) io.WriteCloser {
+	return mwc(wc)
+}
+
+type mwc []io.WriteCloser
+
+func (m mwc) Write(p []byte) (n int, err error) {
+	for _, w := range m {
+		if n, err = w.Write(p); err != nil {
+			return
+		}
+	}
+	return
+}
+func (m mwc) Close() error {
+	for _, w := range m {
+		if err := w.Close(); err != nil {
+			return err
+		}
+	}
+	return nil
+}
diff --git a/log_test.go b/log_test.go
new file mode 100644
index 0000000..06764d6
--- /dev/null
+++ b/log_test.go
@@ -0,0 +1,104 @@
+package log
+
+import (
+	"io/ioutil"
+	"os"
+	"regexp"
+	"testing"
+)
+
+func mustNewFile(t *testing.T) (string, *Logger) {
+	f, err := ioutil.TempFile("", "log_test-")
+	if err != nil {
+		t.Fatalf("failed to create temp file: %v", err)
+	}
+
+	l, err := NewFile(f.Name())
+	if err != nil {
+		t.Fatalf("failed to open new log file: %v", err)
+	}
+
+	return f.Name(), l
+}
+
+func checkContentsMatch(t *testing.T, name, path, expected string) {
+	content, err := ioutil.ReadFile(path)
+	if err != nil {
+		panic(err)
+	}
+
+	got := string(content)
+	if !regexp.MustCompile(expected).Match(content) {
+		t.Errorf("%s: regexp %q did not match %q",
+			name, expected, got)
+	}
+}
+
+func testLogger(t *testing.T, fname string, l *Logger) {
+	l.LogTime = false
+	l.Infof("message %d", 1)
+	checkContentsMatch(t, "info-no-time", fname,
+		"^_ log_test.go:....   message 1\n")
+
+	os.Truncate(fname, 0)
+	l.Infof("message %d\n", 1)
+	checkContentsMatch(t, "info-with-newline", fname,
+		"^_ log_test.go:....   message 1\n")
+
+	os.Truncate(fname, 0)
+	l.LogTime = true
+	l.Infof("message %d", 1)
+	checkContentsMatch(t, "info-with-time", fname,
+		`^\d{8} ..:..:..\.\d{6} _ log_test.go:....   message 1\n`)
+
+	os.Truncate(fname, 0)
+	l.LogTime = false
+	l.Errorf("error %d", 1)
+	checkContentsMatch(t, "error", fname, `^E log_test.go:....   error 1\n`)
+
+	if l.V(Debug) {
+		t.Fatalf("Debug level enabled by default (level: %v)", l.Level)
+	}
+
+	os.Truncate(fname, 0)
+	l.LogTime = false
+	l.Debugf("debug %d", 1)
+	checkContentsMatch(t, "debug-no-log", fname, `^$`)
+
+	os.Truncate(fname, 0)
+	l.Level = Debug
+	l.Debugf("debug %d", 1)
+	checkContentsMatch(t, "debug", fname, `^\. log_test.go:....   debug 1\n`)
+
+	if !l.V(Debug) {
+		t.Errorf("l.Level = Debug, but V(Debug) = false")
+	}
+
+	os.Truncate(fname, 0)
+	l.Level = Info
+	l.Log(Debug, 0, "log debug %d", 1)
+	l.Log(Info, 0, "log info %d", 1)
+	checkContentsMatch(t, "log", fname,
+		`^_ log_test.go:....   log info 1\n`)
+
+}
+
+func TestBasic(t *testing.T) {
+	fname, l := mustNewFile(t)
+	defer l.Close()
+	defer os.Remove(fname)
+
+	testLogger(t, fname, l)
+}
+
+func TestDefaultFile(t *testing.T) {
+	fname, l := mustNewFile(t)
+	l.Close()
+	defer os.Remove(fname)
+
+	*logFile = fname
+
+	Init()
+
+	testLogger(t, fname, Default)
+}