shutdown gracefully without os.Exit (#7480)

* shutdown gracefully without os.Exit

* Update server/util.go

Co-authored-by: Alessio Treglia <quadrispro@ubuntu.com>
Co-authored-by: Alessio Treglia <alessio@tendermint.com>

server/start.go

@@ -179,14 +179,14 @@ func startStandAlone(ctx *Context, appCreator types.AppCreator) error {
 		tmos.Exit(err.Error())
 	}
 
-	TrapSignal(func() {
+	defer func() {
 		if err = svr.Stop(); err != nil {
 			tmos.Exit(err.Error())
 		}
-	})
+	}()
 
-	// run forever (the node will not be returned)
-	select {}
+	// Wait for SIGINT or SIGTERM signal
+	return WaitForQuitSignals()
 }
 
 // legacyAminoCdc is used for the legacy REST API
@@ -290,7 +290,7 @@ func startInProcess(ctx *Context, clientCtx client.Context, appCreator types.App
 		}
 	}
 
-	TrapSignal(func() {
+	defer func() {
 		if tmNode.IsRunning() {
 			_ = tmNode.Stop()
 		}
@@ -308,8 +308,8 @@ func startInProcess(ctx *Context, clientCtx client.Context, appCreator types.App
 		}
 
 		ctx.Logger.Info("exiting...")
-	})
+	}()
 
-	// run forever (the node will not be returned)
-	select {}
+	// Wait for SIGINT or SIGTERM signal
+	return WaitForQuitSignals()
 }

server/util.go

@@ -8,6 +8,7 @@ import (
 	"os"
 	"os/signal"
 	"path/filepath"
+	"strconv"
 	"syscall"
 	"time"
 
@@ -39,6 +40,15 @@ type Context struct {
 	Logger log.Logger
 }
 
+// ErrorCode contains the exit code for server exit.
+type ErrorCode struct {
+	Code int
+}
+
+func (e ErrorCode) Error() string {
+	return strconv.Itoa(e.Code)
+}
+
 func NewDefaultContext() *Context {
 	return NewContext(viper.New(), tmcfg.DefaultConfig(), log.NewTMLogger(log.NewSyncWriter(os.Stdout)))
 }
@@ -245,6 +255,14 @@ func TrapSignal(cleanupFunc func()) {
 	}()
 }
 
+// WaitForQuitSignals waits for SIGINT and SIGTERM and returns.
+func WaitForQuitSignals() ErrorCode {
+	sigs := make(chan os.Signal, 1)
+	signal.Notify(sigs, syscall.SIGINT, syscall.SIGTERM)
+	sig := <-sigs
+	return ErrorCode{Code: int(sig.(syscall.Signal)) + 128}
+}
+
 func skipInterface(iface net.Interface) bool {
 	if iface.Flags&net.FlagUp == 0 {
 		return true // interface down