Reorganize logging

- Move the opening/closing of logs to the log package
- Use conditional compilation for redirecting stdout/err to logfile,
  Unix allows a superior method to Windows
- Panic output will now to go log file on Unix platforms

log/logging.go

@@ -1,7 +1,9 @@
 package log
 
 import (
+	"fmt"
 	golog "log"
+	"os"
 	"strings"
 )
 
@@ -19,8 +21,37 @@ const (
 	TRACE
 )
 
-// MaxLevel is the highest Level we will log (max TRACE, min ERROR)
-var MaxLevel = TRACE
+var (
+	// MaxLevel is the highest Level we will log (max TRACE, min ERROR)
+	MaxLevel = TRACE
+
+	// logfname is the name of the logfile
+	logfname string
+
+	// logf is the file we send log output to, will be nil for stderr or stdout
+	logf *os.File
+)
+
+// Initialize logging.  If logfile is equal to "stderr" or "stdout", then
+// we will log to that output stream.  Otherwise the specificed file will
+// opened for writing, and all log data will be placed in it.
+func Initialize(logfile string) error {
+	if logfile != "stderr" {
+		// stderr is the go logging default
+		if logfile == "stdout" {
+			// set to stdout
+			golog.SetOutput(os.Stdout)
+		} else {
+			logfname = logfile
+			if err := openLogFile(); err != nil {
+				return err
+			}
+			// Platform specific
+			closeStdin()
+		}
+	}
+	return nil
+}
 
 // SetLogLevel sets MaxLevel based on the provided string
 func SetLogLevel(level string) (ok bool) {
@@ -69,3 +100,46 @@ func Tracef(msg string, args ...interface{}) {
 		golog.Printf(msg, args...)
 	}
 }
+
+// Rotate closes the current log file, then reopens it.  This gives an external
+// log rotation system the opportunity to move the existing log file out of the
+// way and have Inbucket create a new one.
+func Rotate() {
+	// Rotate logs if configured
+	if logf != nil {
+		closeLogFile()
+		// There is nothing we can do if the log open fails
+		_ = openLogFile()
+	} else {
+		Infof("Ignoring SIGHUP, logfile not configured")
+	}
+}
+
+// Close the log file if we have one open
+func Close() {
+	if logf != nil {
+		closeLogFile()
+	}
+}
+
+// openLogFile creates or appends to the logfile passed on commandline
+func openLogFile() error {
+	// use specified log file
+	var err error
+	logf, err = os.OpenFile(logfname, os.O_WRONLY|os.O_APPEND|os.O_CREATE, 0666)
+	if err != nil {
+		return fmt.Errorf("Failed to create %v: %v\n", logfname, err)
+	}
+	golog.SetOutput(logf)
+	Tracef("Opened new logfile")
+	// Platform specific
+	reassignStdout()
+	return nil
+}
+
+// closeLogFile closes the current logfile
+func closeLogFile() {
+	Tracef("Closing logfile")
+	// We are never in a situation where we can do anything about failing to close
+	_ = logf.Close()
+}