From ac807ed0b070b1484b8bfd6d6d54b9fbc183807b Mon Sep 17 00:00:00 2001
From: James Hillyerd <james@hillyerd.com>
Date: Mon, 5 Nov 2012 12:50:16 -0800
Subject: [PATCH] Cycle logfiles on SIGHUP for logrotated

---
 inbucket.go | 66 +++++++++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 57 insertions(+), 9 deletions(-)

diff --git a/inbucket.go b/inbucket.go
index 12abe6a..81170c0 100644
--- a/inbucket.go
+++ b/inbucket.go
@@ -13,15 +13,22 @@ import (
 	"github.com/jhillyerd/inbucket/web"
 	golog "log"
 	"os"
+	"os/signal"
+	"syscall"
 	"time"
 )
 
+// Command line flags
 var help = flag.Bool("help", false, "Displays this help")
 var pidfile = flag.String("pidfile", "none", "Write our PID into the specified file")
 var logfile = flag.String("logfile", "stderr", "Write out log into the specified file")
 
+// startTime is used to calculate uptime of Inbucket
 var startTime = time.Now()
 
+// The file we send log output to, will be nil for stderr or stdout
+var logf *os.File
+
 func main() {
 	flag.Parse()
 	if *help {
@@ -40,34 +47,37 @@ func main() {
 		os.Exit(1)
 	}
 
+	// Setup signal handler
+	sigChan := make(chan os.Signal)
+	signal.Notify(sigChan, syscall.SIGHUP)
+	go signalProcessor(sigChan)
+
 	// Configure logging, close std* fds
+	level, _ := config.Config.String("logging", "level")
+	log.SetLogLevel(level)
+
 	if *logfile != "stderr" {
 		// stderr is the go logging default
 		if *logfile == "stdout" {
 			// set to stdout
 			golog.SetOutput(os.Stdout)
 		} else {
-			// use specificed log file
-			logf, err := os.OpenFile(*logfile, os.O_WRONLY | os.O_APPEND | os.O_CREATE, 0666)
+			err = openLogFile()
 			if err != nil {
-				fmt.Fprintf(os.Stderr, "Failed to create %v: %v\n", *logfile, err)
+				fmt.Fprintf(os.Stderr, "%v", err)
 				os.Exit(1)
 			}
-			defer logf.Close()
-			golog.SetOutput(logf)
+			defer closeLogFile()
 
 			// close std* streams
 			os.Stdout.Close()
-			os.Stderr.Close()
+			os.Stderr.Close() // Warning: this will hide panic() output
 			os.Stdin.Close()
 			os.Stdout = logf
 			os.Stderr = logf
 		}
 	}
 
-	level, _ := config.Config.String("logging", "level")
-	log.SetLogLevel(level)
-
 	// Write pidfile if requested
 	// TODO: Probably supposed to remove pidfile during shutdown
 	if *pidfile != "none" {
@@ -87,6 +97,43 @@ func main() {
 	web.Start()
 }
 
+// openLogFile creates or appends to the logfile passed on commandline
+func openLogFile() error {
+	// use specified log file
+	var err error
+	logf, err = os.OpenFile(*logfile, os.O_WRONLY|os.O_APPEND|os.O_CREATE, 0666)
+	if err != nil {
+		return fmt.Errorf("Failed to create %v: %v\n", *logfile, err)
+	}
+	golog.SetOutput(logf)
+	log.Trace("Opened new logfile")
+	return nil
+}
+
+// closeLogFile closes the current logfile
+func closeLogFile() error {
+	log.Trace("Closing logfile")
+	return logf.Close()
+}
+
+// signalProcessor is a goroutine that handles OS signals
+func signalProcessor(c <-chan os.Signal) {
+	for {
+		sig := <-c
+		switch sig {
+		case syscall.SIGHUP:
+			// Rotate logs if configured
+			if logf != nil {
+				log.Info("Recieved SIGHUP, cycling logfile")
+				closeLogFile()
+				openLogFile()
+			} else {
+				log.Info("Ignoring SIGHUP, logfile not configured")
+			}
+		}
+	}
+}
+
 func init() {
 	flag.Usage = func() {
 		fmt.Fprintln(os.Stderr, "Usage of inbucket [options] <conf file>:")
@@ -96,6 +143,7 @@ func init() {
 	expvar.Publish("uptime", expvar.Func(uptime))
 }
 
+// uptime() is published as an expvar
 func uptime() interface{} {
 	return time.Since(startTime) / time.Second
 }