Handle signals first on boot

This handles signals first thing on boot so that plugins are able to
boot with the reaper enabled.

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

cmd/containerd/main.go

@@ -78,9 +78,11 @@ func main() {
 		var (
 			start   = time.Now()
 			signals = make(chan os.Signal, 2048)
+			serverC = make(chan *server.Server)
 			ctx     = log.WithModule(gocontext.Background(), "containerd")
 			config  = defaultConfig()
 		)
+		done := handleSignals(ctx, signals, serverC)
 		// start the signal handler as soon as we can to make sure that
 		// we don't miss any signals during boot
 		signal.Notify(signals, handledSignals...)
@@ -105,6 +107,7 @@ func main() {
 		if err != nil {
 			return err
 		}
+		serverC <- server
 		if config.Debug.Address != "" {
 			l, err := sys.GetLocalListener(config.Debug.Address, config.Debug.Uid, config.Debug.Gid)
 			if err != nil {
@@ -127,7 +130,8 @@ func main() {
 		serve(log.WithModule(ctx, "grpc"), l, server.ServeGRPC)
 
 		log.G(ctx).Infof("containerd successfully booted in %fs", time.Since(start).Seconds())
-		return handleSignals(ctx, signals, server)
+		<-done
+		return nil
 	}
 	if err := app.Run(os.Args); err != nil {
 		fmt.Fprintf(os.Stderr, "containerd: %s\n", err)

cmd/containerd/main_linux.go

@@ -1,39 +0,0 @@
-package main
-
-import (
-	"context"
-	"os"
-
-	"golang.org/x/sys/unix"
-
-	"github.com/containerd/containerd/log"
-	"github.com/containerd/containerd/reaper"
-	"github.com/containerd/containerd/server"
-)
-
-const defaultConfigPath = "/etc/containerd/config.toml"
-
-var handledSignals = []os.Signal{
-	unix.SIGTERM,
-	unix.SIGINT,
-	unix.SIGUSR1,
-	unix.SIGCHLD,
-}
-
-func handleSignals(ctx context.Context, signals chan os.Signal, server *server.Server) error {
-	for s := range signals {
-		log.G(ctx).WithField("signal", s).Debug("received signal")
-		switch s {
-		case unix.SIGCHLD:
-			if err := reaper.Reap(); err != nil {
-				log.G(ctx).WithError(err).Error("reap containerd processes")
-			}
-		case unix.SIGUSR1:
-			dumpStacks()
-		default:
-			server.Stop()
-			return nil
-		}
-	}
-	return nil
-}

cmd/containerd/main_unix.go

@@ -1,4 +1,4 @@
-// +build darwin freebsd solaris
+// +build linux darwin freebsd solaris
 
 package main
 
@@ -23,8 +23,15 @@ var handledSignals = []os.Signal{
 	unix.SIGPIPE,
 }
 
-func handleSignals(ctx context.Context, signals chan os.Signal, server *server.Server) error {
-	for s := range signals {
+func handleSignals(ctx context.Context, signals chan os.Signal, serverC chan *server.Server) chan struct{} {
+	done := make(chan struct{}, 1)
+	go func() {
+		var server *server.Server
+		for {
+			select {
+			case s := <-serverC:
+				server = s
+			case s := <-signals:
 				log.G(ctx).WithField("signal", s).Debug("received signal")
 				switch s {
 				case unix.SIGCHLD:
@@ -36,9 +43,15 @@ func handleSignals(ctx context.Context, signals chan os.Signal, server *server.S
 				case unix.SIGPIPE:
 					continue
 				default:
+					if server == nil {
+						close(done)
+						return
+					}
 					server.Stop()
-			return nil
+					close(done)
 				}
 			}
-	return nil
+		}
+	}()
+	return done
 }

cmd/containerd/main_windows.go

@@ -19,10 +19,24 @@ var (
 	}
 )
 
-func handleSignals(ctx context.Context, signals chan os.Signal, server *server.Server) error {
-	for s := range signals {
+func handleSignals(ctx context.Context, signals chan os.Signal, serverC chan *server.Server) chan struct{} {
+	done := make(chan struct{})
+	go func() {
+		var server *server.Server
+		for {
+			select {
+			case s := <-serverC:
+				server = s
+			case s := <-signals:
 				log.G(ctx).WithField("signal", s).Debug("received signal")
-		server.Stop()
+				if server == nil {
+					close(done)
+					return
 				}
-	return nil
+				server.Stop()
+				close(done)
+			}
+		}
+	}()
+	return done
 }

server/config.go

@@ -87,5 +87,4 @@ func LoadConfig(path string, v *Config) error {
 	}
 	v.md = md
 	return nil
-
 }