Fix a goroutine leak in the signal handler code path

The root cause of this issue was regarding our change to shutting down via
context. While implementating that change set there was a goroutine leak
introduced that did not provide a clean way for shutting down and reloading the
signal handler. This caused signal handling to be duplicated across reloads.

Fixes: #521

core/app.go

@@ -130,7 +130,7 @@ func (a *App) Run() {
 		}()
 
 		a.Bus = events.NewEventBus()
-		a.handleSignals(cancel)
+		a.handleSignals(ctx, cancel)
 		a.ControlServer.Run(ctx, a.Bus)
 		a.runTasks(ctx, completedCh)
 

core/signals.go

@@ -8,20 +8,26 @@ import (
 )
 
 // HandleSignals listens for and captures signals used for orchestration
-func (a *App) handleSignals(cancel context.CancelFunc) {
+func (a *App) handleSignals(ctx context.Context, cancel context.CancelFunc) {
 	recvSig := make(chan os.Signal, 1)
 	signal.Notify(recvSig, syscall.SIGTERM, syscall.SIGINT)
 	go func() {
-		for sig := range recvSig {
-			switch sig {
-			case syscall.SIGINT:
-				a.Terminate()
-				break
-			case syscall.SIGTERM:
-				a.Terminate()
-				break
+		for {
+			select {
+			case sig := <-recvSig:
+				switch sig {
+				case syscall.SIGINT:
+					a.Terminate()
+					return
+				case syscall.SIGTERM:
+					a.Terminate()
+					return
+				default:
+				}
+			case <-ctx.Done():
+				return
+			default:
 			}
 		}
-		cancel()
 	}()
 }

core/signals_test.go

@@ -72,10 +72,10 @@ func TestTerminateSignal(t *testing.T) {
 // Test that only ensures that we cover a straight-line run through
 // the handleSignals setup code
 func TestSignalWiring(t *testing.T) {
-	_, cancel := context.WithCancel(context.Background())
+	ctx, cancel := context.WithCancel(context.Background())
 	app := EmptyApp()
 	app.Bus = events.NewEventBus()
-	app.handleSignals(cancel)
+	app.handleSignals(ctx, cancel)
 	sendAndWaitForSignal(t, syscall.SIGTERM)
 }