Better mqttc exit codes + cleanup.

cmd/mqttc/main.go

@@ -111,19 +111,19 @@ func parseConfig() (clientID string, config *mqtt.Config) {
 
 var exitStatus = make(chan int, 1)
 
-func exitCode(code int) {
+func setExitStatus(code int) {
 	select {
 	case exitStatus <- code:
 	default: // exit status already defined
 	}
 }
 
-func exit(code int) {
-	exitCode(code)
-	err := client.Close()
-	if err != nil {
-		log.Print(err)
+func getExitStatus() (code int) {
+	select {
+	case code = <-exitStatus:
+	default: // stays zero
 	}
+	return
 }
 
 var client *mqtt.Client
@@ -152,7 +152,10 @@ func main() {
 			if err != nil {
 				log.Fatal(err)
 			}
-			err = client.Publish(nil, message, *publishFlag)
+
+			ctx, cancel := context.WithTimeout(context.Background(), *timeoutFlag)
+			defer cancel()
+			err = client.Publish(ctx.Done(), message, *publishFlag)
 			switch {
 			case err == nil:
 				if *verboseFlag {
@@ -160,9 +163,17 @@ func main() {
 				}
 			case errors.Is(err, mqtt.ErrClosed), errors.Is(err, mqtt.ErrDown):
 				return
+			case errors.Is(err, mqtt.ErrCanceled), errors.Is(err, mqtt.ErrAbandoned):
+				log.Printf("%s: publish timeout (%s)", name, err)
+				setExitStatus(1)
+				if err := client.Close(); err != nil {
+					log.Print(err)
+				}
+				return
 			default:
 				log.Print(err)
-				exit(1)
+				setExitStatus(1)
+				_ = client.Close()
 				return
 			}
 		}
@@ -173,20 +184,28 @@ func main() {
 			defer cancel()
 			err := client.SubscribeLimitAtMostOnce(ctx.Done(), subscribeFlags...)
 			switch {
-			case err == nil, errors.Is(err, mqtt.ErrClosed), errors.Is(err, mqtt.ErrDown):
+			case err == nil:
+				if *verboseFlag {
+					log.Printf("%s: subscribed to %d topic filters", name, len(subscribeFlags))
+				}
+			case errors.Is(err, mqtt.ErrClosed), errors.Is(err, mqtt.ErrDown):
 				return
 			case errors.Is(err, mqtt.ErrCanceled), errors.Is(err, mqtt.ErrAbandoned):
-				log.Print(name, ": subscribe timeout")
-
-				fallthrough
+				log.Printf("%s: subscribe timeout (%s)", name, err)
+				setExitStatus(1)
+				if err := client.Close(); err != nil {
+					log.Print(err)
+				}
+				return
 			default:
 				log.Print(err)
-				exitCode(1)
+				setExitStatus(1)
+				_ = client.Close()
 				return
 			}
 		}
 
-		if *publishFlag == "" {
+		if *publishFlag == "" && len(subscribeFlags) == 0 {
 			// ping exchange
 			ctx, cancel := context.WithTimeout(context.Background(), *timeoutFlag)
 			defer cancel()
@@ -197,50 +216,54 @@ func main() {
 			case errors.Is(err, mqtt.ErrClosed), errors.Is(err, mqtt.ErrDown):
 				return
 			case errors.Is(err, mqtt.ErrCanceled), errors.Is(err, mqtt.ErrAbandoned):
-				log.Print(name, ": ping timeout")
-
-				fallthrough
+				log.Printf("%s: ping timeout (%s)", name, err)
+				setExitStatus(1)
+				if err := client.Close(); err != nil {
+					log.Print(err)
+				}
+				return
 			default:
 				log.Print(err)
-				exit(1)
+				setExitStatus(1)
+				_ = client.Close()
 				return
 			}
 		}
 
-		// graceful shutdown
-		ctx, cancel := context.WithTimeout(context.Background(), *timeoutFlag)
-		defer cancel()
-		err := client.Disconnect(ctx.Done())
-		switch {
-		case err == nil:
-			exitCode(0)
-		case errors.Is(err, mqtt.ErrClosed), errors.Is(err, mqtt.ErrDown):
-			break
-		default:
-			log.Print(err)
-			exitCode(1)
+		if len(subscribeFlags) == 0 {
+			// graceful shutdown
+			ctx, cancel := context.WithTimeout(context.Background(), *timeoutFlag)
+			defer cancel()
+			err := client.Disconnect(ctx.Done())
+			switch {
+			case err == nil, errors.Is(err, mqtt.ErrClosed), errors.Is(err, mqtt.ErrDown):
+				break
+			default:
+				log.Print(err)
+				setExitStatus(1)
+				return
+			}
 		}
 	}()
 
+	defer os.Exit(getExitStatus())
+
 	// read routine
+	var big *mqtt.BigMessage
 	for {
-		var big *mqtt.BigMessage
 		message, topic, err := client.ReadSlices()
 		switch {
 		case err == nil:
 			printMessage(message, topic)
 
 		case errors.Is(err, mqtt.ErrClosed):
-			os.Exit(<-exitStatus)
-
-		case mqtt.IsDeny(err): // illegal configuration
-			log.Fatal(err)
+			return
 
 		case errors.As(err, &big):
 			message, err := big.ReadAll()
 			if err != nil {
 				log.Print(err)
-				exit(1)
+				setExitStatus(1)
 				return
 			}
 			printMessage(message, big.Topic)
@@ -261,7 +284,7 @@ func main() {
 				os.Exit(9)
 			}
 
-			exit(1)
+			setExitStatus(1)
 			return
 		}
 	}
@@ -287,16 +310,25 @@ func applySignals() {
 		switch sig {
 		case syscall.SIGINT:
 			log.Print(name, ": SIGINT received; closing connection…")
-			exit(130)
+			setExitStatus(130)
+			switch err := client.Close(); {
+			case err == nil, errors.Is(err, mqtt.ErrDown):
+				break
+			default:
+				log.Print(err)
+			}
 
 		case syscall.SIGTERM:
 			log.Print(name, ": SIGTERM received; sending disconnect…")
-			exitCode(143)
+			setExitStatus(143)
 			ctx, cancel := context.WithTimeout(context.Background(), *timeoutFlag)
 			defer cancel()
-			err := client.Disconnect(ctx.Done())
-			if err != nil && !errors.Is(err, mqtt.ErrClosed) {
+			switch err := client.Disconnect(ctx.Done()); err != nil {
+			case err == nil, errors.Is(err, mqtt.ErrClosed), errors.Is(err, mqtt.ErrDown):
+				break
+			default:
 				log.Print(err)
+				setExitStatus(1)
 			}
 		}
 	}