lnd: switch to nested a main function, fix defer execution

This commit adds a new nested main function “lndMain”, within the
packages’s normal main function. This nesting is required in order to
properly execute all queued defer statements in the case of a forced
exit.

lnd.go

@@ -12,7 +12,6 @@ import (
 	"strconv"
 
 	"google.golang.org/grpc"
-	"google.golang.org/grpc/grpclog"
 
 	"github.com/lightningnetwork/lnd/channeldb"
 	"github.com/lightningnetwork/lnd/lnrpc"
@@ -24,16 +23,15 @@ var (
 	shutdownChannel = make(chan struct{})
 )
 
-func main() {
-	// Use all processor cores.
-	// TODO(roasbeef): remove this if required version # is > 1.6?
-	runtime.GOMAXPROCS(runtime.NumCPU())
-
+// lndMain is the true entry point for lnd. This function is required since
+// defers created in the top-level scope of a main method aren't executed if
+// os.Exit() is called.
+func lndMain() error {
 	// Load the configuration, and parse any command line options. This
 	// function will also set up logging properly.
 	loadedConfig, err := loadConfig()
 	if err != nil {
-		os.Exit(1)
+		return err
 	}
 	cfg = loadedConfig
 	defer backendLog.Flush()
@@ -43,7 +41,7 @@ func main() {
 
 	if loadedConfig.SPVMode == true {
 		shell(loadedConfig.SPVHostAdr, activeNetParams)
-		return
+		return err
 	}
 
 	// Enable http profiling server if requested.
@@ -62,7 +60,7 @@ func main() {
 	chanDB, err := channeldb.Open(loadedConfig.DataDir, activeNetParams)
 	if err != nil {
 		fmt.Println("unable to open channeldb: ", err)
-		os.Exit(1)
+		return err
 	}
 	defer chanDB.Close()
 
@@ -70,12 +68,12 @@ func main() {
 	f, err := os.Open(loadedConfig.RPCCert)
 	if err != nil {
 		fmt.Fprintln(os.Stderr, err)
-		os.Exit(1)
+		return err
 	}
 	cert, err := ioutil.ReadAll(f)
 	if err != nil {
 		fmt.Fprintln(os.Stderr, err)
-		os.Exit(1)
+		return err
 	}
 	defer f.Close()
 
@@ -93,11 +91,11 @@ func main() {
 	wallet, err := lnwallet.NewLightningWallet(config, chanDB)
 	if err != nil {
 		fmt.Printf("unable to create wallet: %v\n", err)
-		os.Exit(1)
+		return err
 	}
 	if err := wallet.Startup(); err != nil {
 		fmt.Printf("unable to start wallet: %v\n", err)
-		os.Exit(1)
+		return err
 	}
 	ltndLog.Info("LightningWallet opened")
 
@@ -112,7 +110,7 @@ func main() {
 	server, err := newServer(defaultListenAddrs, wallet, chanDB)
 	if err != nil {
 		srvrLog.Errorf("unable to create server: %v\n", err)
-		os.Exit(1)
+		return err
 	}
 	server.Start()
 
@@ -130,9 +128,8 @@ func main() {
 	// Finally, start the grpc server listening for HTTP/2 connections.
 	lis, err := net.Listen("tcp", fmt.Sprintf(":%d", loadedConfig.RPCPort))
 	if err != nil {
-		grpclog.Fatalf("failed to listen: %v", err)
 		fmt.Printf("failed to listen: %v", err)
-		os.Exit(1)
+		return err
 	}
 	go func() {
 		rpcsLog.Infof("RPC server listening on %s", lis.Addr())
@@ -143,4 +140,17 @@ func main() {
 	// the interrupt handler.
 	<-shutdownChannel
 	ltndLog.Info("Shutdown complete")
+	return nil
+}
+
+func main() {
+	// Use all processor cores.
+	// TODO(roasbeef): remove this if required version # is > 1.6?
+	runtime.GOMAXPROCS(runtime.NumCPU())
+
+	// Call the "real" main in a nested manner so the defers will properly
+	// be executed in the case of a graceful shutdown.
+	if err := lndMain(); err != nil {
+		os.Exit(1)
+	}
 }