Add two features in gplog (#43)

* Add two features in gplog

- A new function FatalWithoutPanic, same as Fatal but will not
  panic and will exit(1)
- Enable user to customize the log file name

* Add comment and change FatalWithoutPanic errorCode to 2.

* Add test cases & FatalWithoutPanic can mock exit function

gplog/gplog.go

@@ -36,6 +36,11 @@ var (
 	 * arise while running tests in parallel.
 	 */
 	logMutex sync.Mutex
+	/*
+	 * A function which can customize log file name
+	 */
+	logFileNameFunc		LogFileNameFunc
+	exitFunc	   		ExitFunc
 )
 
 const (
@@ -75,8 +80,11 @@ const (
  * - Fatal: Messages indicating that the program cannot proceed, e.g. the database
  *          cannot be reached.  This function will exit the program after printing
  *          the error message.
+ * - FatalWithoutPanic: Same as Fatal, but will not trigger panic. Just exit(1).
  */
 type LogPrefixFunc func(string) string
+type LogFileNameFunc func(string, string) string
+type ExitFunc func()
 
 type GpLogger struct {
 	logStdout      *log.Logger
@@ -108,11 +116,23 @@ func InitializeLogging(program string, logdir string) {
 	}
 
 	createLogDirectory(logdir)
-	timestamp := operating.System.Now().Format("20060102")
-	logfile := fmt.Sprintf("%s/%s_%s.log", logdir, program, timestamp)
+
+	logfile := GenerateLogFileName(program, logdir)
 	logFileHandle := openLogFile(logfile)
 
 	logger = NewLogger(os.Stdout, os.Stderr, logFileHandle, logfile, LOGINFO, program)
+	SetExitFunc(defaultExit)
+}
+
+func GenerateLogFileName(program, logdir string) string {
+	var logfile string
+	if logFileNameFunc != nil {
+		logfile = logFileNameFunc(program, logdir)
+	} else {
+		timestamp := operating.System.Now().Format("20060102")
+		logfile = fmt.Sprintf("%s/%s_%s.log", logdir, program, timestamp)
+	}
+	return logfile
 }
 
 func SetLogger(log *GpLogger) {
@@ -157,6 +177,14 @@ func SetLogPrefixFunc(logPrefixFunc func(string) string) {
 	logger.logPrefixFunc = logPrefixFunc
 }
 
+func SetLogFileNameFunc(fileNameFunc func(string, string) string) {
+	logFileNameFunc = fileNameFunc
+}
+
+func SetExitFunc(pExitFunc func()) {
+	exitFunc = pExitFunc
+}
+
 func defaultLogPrefixFunc(level string) string {
 	logTimestamp := operating.System.Now().Format("20060102:15:04:05")
 	return fmt.Sprintf("%s %s", logTimestamp, fmt.Sprintf(logger.header, level))
@@ -286,6 +314,16 @@ func FatalOnError(err error, output ...string) {
 	}
 }
 
+func FatalWithoutPanic(s string, v ...interface{}) {
+	logMutex.Lock()
+	defer logMutex.Unlock()
+	message := GetLogPrefix("CRITICAL") + fmt.Sprintf(s, v...)
+	errorCode = 2
+	_ = logger.logFile.Output(1, message)
+	_ = logger.logStderr.Output(1, message)
+	exitFunc()
+}
+
 type stackTracer interface {
 	StackTrace() errors.StackTrace
 }
@@ -338,3 +376,7 @@ func createLogDirectory(dirname string) {
 		abort(errors.Errorf("%s is a file, not a directory", dirname))
 	}
 }
+
+func defaultExit() {
+	os.Exit(1)
+}

gplog/gplog_test.go

@@ -499,6 +499,16 @@ var _ = Describe("logger/log tests", func() {
 					gplog.Fatal(errors.New(expectedMessage), "")
 				})
 			})
+			Context("FatalWithoutPanic", func() {
+				It("prints to the log file, then exit(1)", func() {
+					gplog.SetExitFunc(func() {})
+					expectedMessage := "logfile error fatalwithoutpanic"
+					gplog.FatalWithoutPanic(expectedMessage)
+					testhelper.NotExpectRegexp(stdout, fatalExpected+expectedMessage)
+					testhelper.ExpectRegexp(stderr, fatalExpected+expectedMessage)
+					testhelper.ExpectRegexp(logfile, fatalExpected+expectedMessage)
+				})
+			})
 		})
 	})
 })