Extract a LogTarget interface to make it easier to manage logging

cmd/grumble/grumble.go

@@ -44,7 +44,7 @@ func main() {
 	}
 	log.SetPrefix("[G] ")
 	log.SetFlags(log.LstdFlags | log.Lmicroseconds)
-	log.SetOutput(&logtarget.Target)
+	log.SetOutput(logtarget.Target)
 	log.Printf("Grumble")
 	log.Printf("Using data directory: %s", Args.DataDir)
 

cmd/grumble/server.go

@@ -156,7 +156,7 @@ func NewServer(id int64) (s *Server, err error) {
 	s.Channels[0] = NewChannel(0, "Root")
 	s.nextChanId = 1
 
-	s.Logger = log.New(&logtarget.Target, fmt.Sprintf("[%v] ", s.Id), log.LstdFlags|log.Lmicroseconds)
+	s.Logger = log.New(logtarget.Target, fmt.Sprintf("[%v] ", s.Id), log.LstdFlags|log.Lmicroseconds)
 
 	return
 }

pkg/logtarget/logtarget.go

@@ -7,15 +7,23 @@ package logtarget
 
 import (
 	"bytes"
+	"io"
 	"os"
 	"sync"
 )
 
+type LogTarget interface {
+	io.Writer
+
+	OpenFile(string) error
+	Rotate() error
+}
+
 // LogTarget implements the io.Writer interface, allowing
 // LogTarget to be registered with the regular Go log package.
 // LogTarget multiplexes its incoming writes to multiple optional
 // output writers, and one main output writer (the log file).
-type LogTarget struct {
+type FileLogTarget struct {
 	mu     sync.Mutex
 	logfn  string
 	file   *os.File
@@ -24,8 +32,12 @@ type LogTarget struct {
 
 var Target LogTarget
 
+func init() {
+	Target = &FileLogTarget{}
+}
+
 // Write writes a log message to all registered io.Writers
-func (target *LogTarget) Write(in []byte) (int, error) {
+func (target *FileLogTarget) Write(in []byte) (int, error) {
 	target.mu.Lock()
 	defer target.mu.Unlock()
 
@@ -48,7 +60,7 @@ func (target *LogTarget) Write(in []byte) (int, error) {
 
 // OpenFile opens the main log file for writing.
 // This method will open the file in append-only mode.
-func (target *LogTarget) OpenFile(fn string) (err error) {
+func (target *FileLogTarget) OpenFile(fn string) (err error) {
 	target.logfn = fn
 	target.file, err = os.OpenFile(target.logfn, os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0650)
 	if err != nil {
@@ -61,7 +73,7 @@ func (target *LogTarget) OpenFile(fn string) (err error) {
 // This method holds a lock while rotating the log file,
 // and all log writes will be held back until the rotation
 // is complete.
-func (target *LogTarget) Rotate() error {
+func (target *FileLogTarget) Rotate() error {
 	target.mu.Lock()
 	defer target.mu.Unlock()