Revert "Use a monitor process to handle panics and restarts (fixes #586)"v0.9.12v0.9-nomonitor

This reverts commit 10f071325726e8de1d44ec9ea1a7a9741f885c6d.

Conflicts:
	cmd/syncthing/monitor.go

4 files changed, 91 insertions, 193 deletions

diff --git a/cmd/syncthing/heapprof.go b/cmd/syncthing/heapprof.go
index a4631451f..24e0e522c 100644
--- a/cmd/syncthing/heapprof.go
+++ b/cmd/syncthing/heapprof.go
@@ -14,8 +14,7 @@ import (
 )
 
 func init() {
-	if innerProcess && os.Getenv("STHEAPPROFILE") != "" {
-		l.Debugln("Starting heap profiling")
+	if os.Getenv("STHEAPPROFILE") != "" {
 		go saveHeapProfiles()
 	}
 }
diff --git a/cmd/syncthing/main.go b/cmd/syncthing/main.go
index 61f3d6784..f04add856 100644
--- a/cmd/syncthing/main.go
+++ b/cmd/syncthing/main.go
@@ -16,6 +16,7 @@ import (
 	"net/http"
 	_ "net/http/pprof"
 	"os"
+	"os/exec"
 	"path/filepath"
 	"regexp"
 	"runtime"
@@ -52,15 +53,7 @@ var (
 	GoArchExtra string // "", "v5", "v6", "v7"
 )
 
-const (
-	exitSuccess            = 0
-	exitError              = 1
-	exitNoUpgradeAvailable = 2
-	exitRestarting         = 3
-)
-
 var l = logger.DefaultLogger
-var innerProcess = os.Getenv("STNORESTART") != ""
 
 func init() {
 	if Version != "unknown-dev" {
@@ -88,8 +81,10 @@ var (
 	confDir      string
 	logFlags     int = log.Ltime
 	rateBucket   *ratelimit.Bucket
-	stop         = make(chan int)
+	stop         = make(chan bool)
 	discoverer   *discover.Discoverer
+	lockConn     *net.TCPListener
+	lockPort     int
 	externalPort int
 	cert         tls.Certificate
 )
@@ -158,20 +153,16 @@ func init() {
 	rand.Seed(time.Now().UnixNano())
 }
 
-// Command line options
-var (
-	reset             bool
-	showVersion       bool
-	doUpgrade         bool
-	doUpgradeCheck    bool
-	noBrowser         bool
-	generateDir       string
-	guiAddress        string
-	guiAuthentication string
-	guiAPIKey         string
-)
-
 func main() {
+	var reset bool
+	var showVersion bool
+	var doUpgrade bool
+	var doUpgradeCheck bool
+	var noBrowser bool
+	var generateDir string
+	var guiAddress string
+	var guiAuthentication string
+	var guiAPIKey string
 	flag.StringVar(&confDir, "home", getDefaultConfDir(), "Set configuration directory")
 	flag.BoolVar(&reset, "reset", false, "Prepare to resync from cluster")
 	flag.BoolVar(&showVersion, "version", false, "Show version")
@@ -226,7 +217,7 @@ func main() {
 
 		if upgrade.CompareVersions(rel.Tag, Version) <= 0 {
 			l.Infof("No upgrade available (current %q >= latest %q).", Version, rel.Tag)
-			os.Exit(exitNoUpgradeAvailable)
+			os.Exit(2)
 		}
 
 		l.Infof("Upgrade available (current %q < latest %q)", Version, rel.Tag)
@@ -243,20 +234,11 @@ func main() {
 		}
 	}
 
-	if reset {
-		resetRepositories()
-		return
-	}
-
-	if os.Getenv("STNORESTART") != "" {
-		syncthingMain()
-	} else {
-		monitorMain()
-	}
-}
-
-func syncthingMain() {
 	var err error
+	lockPort, err = getLockPort()
+	if err != nil {
+		l.Fatalln("Opening lock port:", err)
+	}
 
 	if len(os.Getenv("GOGC")) == 0 {
 		debug.SetGCPercent(25)
@@ -270,7 +252,7 @@ func syncthingMain() {
 
 	events.Default.Log(events.Starting, map[string]string{"home": confDir})
 
-	if _, err = os.Stat(confDir); err != nil && confDir == getDefaultConfDir() {
+	if _, err := os.Stat(confDir); err != nil && confDir == getDefaultConfDir() {
 		// We are supposed to use the default configuration directory. It
 		// doesn't exist. In the past our default has been ~/.syncthing, so if
 		// that directory exists we move it to the new default location and
@@ -365,6 +347,15 @@ func syncthingMain() {
 		l.Infof("Edit %s to taste or use the GUI\n", cfgFile)
 	}
 
+	if reset {
+		resetRepositories()
+		return
+	}
+
+	if len(os.Getenv("STRESTART")) > 0 {
+		waitForParentExit()
+	}
+
 	if profiler := os.Getenv("STPROFILER"); len(profiler) > 0 {
 		go func() {
 			l.Debugln("Starting profiler on", profiler)
@@ -595,10 +586,9 @@ nextRepo:
 	events.Default.Log(events.StartupComplete, nil)
 	go generateEvents()
 
-	code := <-stop
+	<-stop
 
 	l.Okln("Exiting")
-	os.Exit(code)
 }
 
 func generateEvents() {
@@ -608,6 +598,25 @@ func generateEvents() {
 	}
 }
 
+func waitForParentExit() {
+	l.Infoln("Waiting for parent to exit...")
+	lockPortStr := os.Getenv("STRESTART")
+	lockPort, err := strconv.Atoi(lockPortStr)
+	if err != nil {
+		l.Warnln("Invalid lock port %q: %v", lockPortStr, err)
+	}
+	// Wait for the listen address to become free, indicating that the parent has exited.
+	for {
+		ln, err := net.Listen("tcp", fmt.Sprintf("127.0.0.1:%d", lockPort))
+		if err == nil {
+			ln.Close()
+			break
+		}
+		time.Sleep(250 * time.Millisecond)
+	}
+	l.Infoln("Continuing")
+}
+
 func setupUPnP() {
 	if len(cfg.Options.ListenAddress) == 1 {
 		_, portStr, err := net.SplitHostPort(cfg.Options.ListenAddress[0])
@@ -737,12 +746,40 @@ func archiveLegacyConfig() {
 
 func restart() {
 	l.Infoln("Restarting")
-	stop <- exitRestarting
+	if os.Getenv("SMF_FMRI") != "" || os.Getenv("STNORESTART") != "" {
+		// Solaris SMF
+		l.Infoln("Service manager detected; exit instead of restart")
+		stop <- true
+		return
+	}
+
+	env := os.Environ()
+	newEnv := make([]string, 0, len(env))
+	for _, s := range env {
+		if !strings.HasPrefix(s, "STRESTART=") {
+			newEnv = append(newEnv, s)
+		}
+	}
+	newEnv = append(newEnv, fmt.Sprintf("STRESTART=%d", lockPort))
+
+	pgm, err := exec.LookPath(os.Args[0])
+	if err != nil {
+		l.Warnln("Cannot restart:", err)
+		return
+	}
+	proc, err := os.StartProcess(pgm, os.Args, &os.ProcAttr{
+		Env:   newEnv,
+		Files: []*os.File{os.Stdin, os.Stdout, os.Stderr},
+	})
+	if err != nil {
+		l.Fatalln(err)
+	}
+	proc.Release()
+	stop <- true
 }
 
 func shutdown() {
-	l.Infoln("Shutting down")
-	stop <- exitSuccess
+	stop <- true
 }
 
 var saveConfigCh = make(chan struct{})
@@ -1096,6 +1133,16 @@ func getFreePort(host string, ports ...int) (int, error) {
 	return addr.Port, nil
 }
 
+func getLockPort() (int, error) {
+	var err error
+	lockConn, err = net.ListenTCP("tcp", &net.TCPAddr{IP: net.IP{127, 0, 0, 1}})
+	if err != nil {
+		return 0, err
+	}
+	addr := lockConn.Addr().(*net.TCPAddr)
+	return addr.Port, nil
+}
+
 func overrideGUIConfig(originalCfg config.GUIConfiguration, address, authentication, apikey string) config.GUIConfiguration {
 	// Make a copy of the config
 	cfg := originalCfg
diff --git a/cmd/syncthing/monitor.go b/cmd/syncthing/monitor.go
deleted file mode 100644
index 0f3cbf2ce..000000000
--- a/cmd/syncthing/monitor.go
+++ /dev/null
@@ -1,148 +0,0 @@
-// Copyright (C) 2014 Jakob Borg and Contributors (see the CONTRIBUTORS file).
-// All rights reserved. Use of this source code is governed by an MIT-style
-// license that can be found in the LICENSE file.
-
-package main
-
-import (
-	"bufio"
-	"io"
-	"os"
-	"os/exec"
-	"path/filepath"
-	"strings"
-	"sync"
-	"time"
-)
-
-var (
-	stdoutFirstLines []string // The first 10 lines of stdout
-	stdoutLastLines  []string // The last 50 lines of stdout
-	stdoutMut        sync.Mutex
-)
-
-const (
-	countRestarts = 5
-	loopThreshold = 15 * time.Second
-)
-
-func monitorMain() {
-	os.Setenv("STNORESTART", "yes")
-	l.SetPrefix("[monitor] ")
-
-	args := os.Args
-	var restarts [countRestarts]time.Time
-
-	for {
-		if t := time.Since(restarts[0]); t < loopThreshold {
-			l.Warnf("%d restarts in %v; not retrying further", countRestarts, t)
-			os.Exit(exitError)
-		}
-
-		copy(restarts[0:], restarts[1:])
-		restarts[len(restarts)-1] = time.Now()
-
-		cmd := exec.Command(args[0], args[1:]...)
-
-		stderr, err := cmd.StderrPipe()
-		if err != nil {
-			l.Fatalln(err)
-		}
-
-		stdout, err := cmd.StdoutPipe()
-		if err != nil {
-			l.Fatalln(err)
-		}
-
-		l.Infoln("Starting syncthing")
-		err = cmd.Start()
-		if err != nil {
-			l.Fatalln(err)
-		}
-
-		stdoutMut.Lock()
-		stdoutFirstLines = make([]string, 0, 10)
-		stdoutLastLines = make([]string, 0, 50)
-		stdoutMut.Unlock()
-
-		go copyStderr(stderr)
-		go copyStdout(stdout)
-
-		err = cmd.Wait()
-		if err == nil {
-			// Successfull exit indicates an intentional shutdown
-			return
-		}
-
-		l.Infoln("Syncthing exited:", err)
-		time.Sleep(1 * time.Second)
-	}
-}
-
-func copyStderr(stderr io.ReadCloser) {
-	br := bufio.NewReader(stderr)
-
-	var panicFd *os.File
-	for {
-		line, err := br.ReadString('\n')
-		if err != nil {
-			if err != io.EOF {
-				l.Warnln("stderr:", err)
-			}
-			return
-		}
-
-		if panicFd == nil {
-			os.Stderr.WriteString(line)
-
-			if strings.HasPrefix(line, "panic:") || strings.HasPrefix(line, "fatal error:") {
-				panicFd, err = os.Create(filepath.Join(confDir, time.Now().Format("panic-20060102-150405.log")))
-				if err != nil {
-					l.Warnln("Create panic log:", err)
-					continue
-				}
-
-				l.Warnf("Panic detected, writing to \"%s\"", panicFd.Name())
-				l.Warnln("Please create an issue at https://github.com/syncting/syncthing/issues/ with the panic log attached")
-
-				stdoutMut.Lock()
-				for _, line := range stdoutFirstLines {
-					panicFd.WriteString(line)
-				}
-				panicFd.WriteString("...\n")
-				for _, line := range stdoutLastLines {
-					panicFd.WriteString(line)
-				}
-			}
-		}
-
-		if panicFd != nil {
-			panicFd.WriteString(line)
-		}
-	}
-}
-
-func copyStdout(stderr io.ReadCloser) {
-	br := bufio.NewReader(stderr)
-	for {
-		line, err := br.ReadString('\n')
-		if err != nil {
-			if err != io.EOF {
-				l.Warnln("stdout:", err)
-			}
-			return
-		}
-
-		stdoutMut.Lock()
-		if len(stdoutFirstLines) < cap(stdoutFirstLines) {
-			stdoutFirstLines = append(stdoutFirstLines, line)
-		}
-		if l := len(stdoutLastLines); l == cap(stdoutLastLines) {
-			stdoutLastLines = stdoutLastLines[:l-1]
-		}
-		stdoutLastLines = append(stdoutLastLines, line)
-		stdoutMut.Unlock()
-
-		os.Stdout.WriteString(line)
-	}
-}
diff --git a/cmd/syncthing/perfstats_unix.go b/cmd/syncthing/perfstats_unix.go
index 48746a6a8..403de2693 100644
--- a/cmd/syncthing/perfstats_unix.go
+++ b/cmd/syncthing/perfstats_unix.go
@@ -15,7 +15,7 @@ import (
 )
 
 func init() {
-	if innerProcess && os.Getenv("STPERFSTATS") != "" {
+	if os.Getenv("STPERFSTATS") != "" {
 		go savePerfStats(fmt.Sprintf("perfstats-%d.csv", syscall.Getpid()))
 	}
 }