build: upgrade to go 1.17 and dependencies

vendor/github.com/eclipse/paho.mqtt.golang/router.go

@@ -37,17 +37,11 @@ type route struct {
 // and returns a boolean of the outcome
 func match(route []string, topic []string) bool {
 	if len(route) == 0 {
-		if len(topic) == 0 {
-			return true
-		}
-		return false
+		return len(topic) == 0
 	}
 
 	if len(topic) == 0 {
-		if route[0] == "#" {
-			return true
-		}
-		return false
+		return route[0] == "#"
 	}
 
 	if route[0] == "#" {
@@ -87,15 +81,13 @@ type router struct {
 	routes         *list.List
 	defaultHandler MessageHandler
 	messages       chan *packets.PublishPacket
-	stop           chan bool
 }
 
 // newRouter returns a new instance of a Router and channel which can be used to tell the Router
 // to stop
-func newRouter() (*router, chan bool) {
-	router := &router{routes: list.New(), messages: make(chan *packets.PublishPacket), stop: make(chan bool)}
-	stop := router.stop
-	return router, stop
+func newRouter() *router {
+	router := &router{routes: list.New(), messages: make(chan *packets.PublishPacket)}
+	return router
 }
 
 // addRoute takes a topic string and MessageHandler callback. It looks in the current list of
@@ -105,7 +97,7 @@ func (r *router) addRoute(topic string, callback MessageHandler) {
 	r.Lock()
 	defer r.Unlock()
 	for e := r.routes.Front(); e != nil; e = e.Next() {
-		if e.Value.(*route).match(topic) {
+		if e.Value.(*route).topic == topic {
 			r := e.Value.(*route)
 			r.callback = callback
 			return
@@ -120,7 +112,7 @@ func (r *router) deleteRoute(topic string) {
 	r.Lock()
 	defer r.Unlock()
 	for e := r.routes.Front(); e != nil; e = e.Next() {
-		if e.Value.(*route).match(topic) {
+		if e.Value.(*route).topic == topic {
 			r.routes.Remove(e)
 			return
 		}
@@ -139,49 +131,99 @@ func (r *router) setDefaultHandler(handler MessageHandler) {
 // takes messages off the channel, matches them against the internal route list and calls the
 // associated callback (or the defaultHandler, if one exists and no other route matched). If
 // anything is sent down the stop channel the function will end.
-func (r *router) matchAndDispatch(messages <-chan *packets.PublishPacket, order bool, client *client) {
-	go func() {
-		for {
-			select {
-			case message := <-messages:
-				sent := false
-				r.RLock()
-				m := messageFromPublish(message, client.ackFunc(message))
-				handlers := []MessageHandler{}
-				for e := r.routes.Front(); e != nil; e = e.Next() {
-					if e.Value.(*route).match(message.TopicName) {
-						if order {
-							handlers = append(handlers, e.Value.(*route).callback)
-						} else {
-							hd := e.Value.(*route).callback
-							go func() {
-								hd(client, m)
-								m.Ack()
-							}()
+func (r *router) matchAndDispatch(messages <-chan *packets.PublishPacket, order bool, client *client) <-chan *PacketAndToken {
+	var wg sync.WaitGroup
+	ackOutChan := make(chan *PacketAndToken) // Channel returned to caller; closed when messages channel closed
+	var ackInChan chan *PacketAndToken       // ACKs generated by ackFunc get put onto this channel
+
+	stopAckCopy := make(chan struct{})    // Closure requests stop of go routine copying ackInChan to ackOutChan
+	ackCopyStopped := make(chan struct{}) // Closure indicates that it is safe to close ackOutChan
+	goRoutinesDone := make(chan struct{}) // closed on wg.Done()
+	if order {
+		ackInChan = ackOutChan // When order = true no go routines are used so safe to use one channel and close when done
+	} else {
+		// When order = false ACK messages are sent in go routines so ackInChan cannot be closed until all goroutines done
+		ackInChan = make(chan *PacketAndToken)
+		go func() { // go routine to copy from ackInChan to ackOutChan until stopped
+			for {
+				select {
+				case a := <-ackInChan:
+					ackOutChan <- a
+				case <-stopAckCopy:
+					close(ackCopyStopped) // Signal main go routine that it is safe to close ackOutChan
+					for {
+						select {
+						case <-ackInChan: // drain ackInChan to ensure all goRoutines can complete cleanly (ACK dropped)
+							DEBUG.Println(ROU, "matchAndDispatch received acknowledgment after processing stopped (ACK dropped).")
+						case <-goRoutinesDone:
+							close(ackInChan) // Nothing further should be sent (a panic is probably better than silent failure)
+							DEBUG.Println(ROU, "matchAndDispatch order=false copy goroutine exiting.")
+							return
 						}
-						sent = true
 					}
 				}
-				if !sent && r.defaultHandler != nil {
+			}
+		}()
+	}
+
+	go func() { // Main go routine handling inbound messages
+		for message := range messages {
+			// DEBUG.Println(ROU, "matchAndDispatch received message")
+			sent := false
+			r.RLock()
+			m := messageFromPublish(message, ackFunc(ackInChan, client.persist, message))
+			var handlers []MessageHandler
+			for e := r.routes.Front(); e != nil; e = e.Next() {
+				if e.Value.(*route).match(message.TopicName) {
+					if order {
+						handlers = append(handlers, e.Value.(*route).callback)
+					} else {
+						hd := e.Value.(*route).callback
+						wg.Add(1)
+						go func() {
+							hd(client, m)
+							m.Ack()
+							wg.Done()
+						}()
+					}
+					sent = true
+				}
+			}
+			if !sent {
+				if r.defaultHandler != nil {
 					if order {
 						handlers = append(handlers, r.defaultHandler)
 					} else {
+						wg.Add(1)
 						go func() {
 							r.defaultHandler(client, m)
 							m.Ack()
+							wg.Done()
 						}()
 					}
+				} else {
+					DEBUG.Println(ROU, "matchAndDispatch received message and no handler was available. Message will NOT be acknowledged.")
 				}
-				r.RUnlock()
-				for _, handler := range handlers {
-					func() {
-						handler(client, m)
-						m.Ack()
-					}()
-				}
-			case <-r.stop:
-				return
 			}
+			r.RUnlock()
+			for _, handler := range handlers {
+				handler(client, m)
+				m.Ack()
+			}
+			// DEBUG.Println(ROU, "matchAndDispatch handled message")
 		}
+		if order {
+			close(ackOutChan)
+		} else { // Ensure that nothing further will be written to ackOutChan before closing it
+			close(stopAckCopy)
+			<-ackCopyStopped
+			close(ackOutChan)
+			go func() {
+				wg.Wait() // Note: If this remains running then the user has handlers that are not returning
+				close(goRoutinesDone)
+			}()
+		}
+		DEBUG.Println(ROU, "matchAndDispatch exiting")
 	}()
+	return ackOutChan
 }