每个hub单独维护自己的运行状态，没有客户端的时候，停止kafka客户端接收

serv.go

@@ -6,6 +6,7 @@ import (
 	"net/http"
 	"os"
 	"os/signal"
+	"strconv"
 	"strings"
 	"syscall"
 	"time"
@@ -43,7 +44,6 @@ var (
 		WriteBufferSize: 1024,
 	}
 	hubMap = make(map[string]Hub)
-	run    = true
 )
 
 // Client is a middleman between the websocket connection and the hub.
@@ -57,14 +57,15 @@ type Client struct {
 	send chan []byte
 }
 
-func create(topic string) *kafka.Reader {
+func create(topic string, offset int64) *kafka.Reader {
 	group, _ := uuid.NewV4()
 
 	log.WithFields(log.Fields{
 		"topic":             topic,
 		"bootstrap servers": *bootstrapServers,
 		"partition":         *partition,
-		"group":             group}).Info("creating kafka client ... ")
+		"group":             group,
+		"offset":            offset}).Info("creating kafka client ... ")
 
 	reader := kafka.NewReader(kafka.ReaderConfig{
 		Brokers:   strings.Split(*bootstrapServers, ","),
@@ -73,7 +74,7 @@ func create(topic string) *kafka.Reader {
 		MinBytes:  10e1,
 		MaxBytes:  10e6, // 10MB
 	})
-	reader.SetOffset(-1) //latest offset
+	reader.SetOffset(offset)
 
 	return reader
 }
@@ -95,22 +96,17 @@ func (c *Client) readPump() {
 
 	sigchan := make(chan os.Signal, 1)
 	signal.Notify(sigchan, syscall.SIGINT, syscall.SIGTERM)
-
+	run := true
 	for run == true {
 		select {
 		case sig := <-sigchan:
 			log.WithFields(log.Fields{"signal": sig}).Info(" terminating")
 			run = false
+			for topic, hub := range hubMap {
+				log.WithField("topic", topic).Warn("closing hub")
+				hub.running = false
+			}
 			log.Fatal("break ")
-			// default:
-			// for {
-			// 	m, err := c.hub.reader.ReadMessage(context.Background())
-			// 	if err != nil {
-			// 		log.WithFields(log.Fields{"error": err}).Error("read error")
-			// 	}
-			// 	log.WithFields(log.Fields{"offset": m.Offset, "message": string(m.Value)}).Info("got message")
-			// 	c.hub.broadcast <- m.Value
-			// }
 		}
 	}
 
@@ -126,6 +122,8 @@ func (c *Client) writePump() {
 	defer func() {
 		ticker.Stop()
 		c.conn.Close()
+		c.hub.unregister <- c
+		log.WithField("client", c).Warn("exit")
 	}()
 	for {
 		select {
@@ -166,18 +164,21 @@ func (c *Client) writePump() {
 func serveWs(w http.ResponseWriter, r *http.Request) {
 	vars := mux.Vars(r)
 	topic := vars["topic"]
+	offsetString := vars["offset"]
+	offset, _ := strconv.ParseInt(offsetString, 10, 64)
 
 	conn, err := upgrader.Upgrade(w, r, nil)
 	if err != nil {
 		log.Error("upgrade connection failed ", err)
 		return
 	}
-	h, ok := hubMap[topic]
+	key := topic + "|" + offsetString
+	h, ok := hubMap[key]
 	if !ok {
-		log.WithField("topic", topic).Info("create new hub ")
-		h = *newHub(topic)
+		log.WithFields(log.Fields{"topic": topic, "offset": offset}).Info("create new hub ")
+		h = *newHub(topic, offset)
 		go h.run()
-		hubMap[topic] = h
+		hubMap[key] = h
 	} else {
 		log.Info("join hub")
 	}
@@ -193,6 +194,12 @@ func serveWs(w http.ResponseWriter, r *http.Request) {
 // Hub maintains the set of active clients and broadcasts messages to the
 // clients.
 type Hub struct {
+	running bool
+
+	topic string
+
+	offset int64
+
 	reader *kafka.Reader
 
 	// Registered clients.
@@ -208,9 +215,11 @@ type Hub struct {
 	unregister chan *Client
 }
 
-func newHub(topic string) *Hub {
+func newHub(topic string, offset int64) *Hub {
 	return &Hub{
-		reader:     create(topic),
+		running:    true,
+		topic:      topic,
+		offset:     offset,
 		broadcast:  make(chan []byte),
 		register:   make(chan *Client),
 		unregister: make(chan *Client),
@@ -218,20 +227,33 @@ func newHub(topic string) *Hub {
 	}
 }
 func (h *Hub) read() {
-	log.WithField("reader", h.reader).Info("start to read")
-	for run == true {
+	log.WithField("hub", *h).Info("start to read")
+	for h.running == true {
+
+		if h.reader == nil {
+			h.reader = create(h.topic, h.offset)
+			time.Sleep(5 * time.Second)
+		}
 		m, err := h.reader.ReadMessage(context.Background())
 		if err != nil {
 			log.WithFields(log.Fields{"error": err}).Error("read error")
+			h.reader.Close()
+			h.reader = nil
+		} else {
+			log.WithFields(log.Fields{"offset": m.Offset, "message": string(m.Value)}).Info("got message")
+			h.broadcast <- m.Value
 		}
-		log.WithFields(log.Fields{"offset": m.Offset, "message": string(m.Value)}).Info("got message")
-		h.broadcast <- m.Value
+
 	}
 }
 
+func (h *Hub) getKey() string {
+	return h.topic + "|" + strconv.FormatInt(h.offset, 10)
+}
+
 func (h *Hub) run() {
 	go h.read()
-	for run == true {
+	for h.running == true {
 		select {
 		case client := <-h.register:
 			h.clients[client] = true
@@ -239,6 +261,14 @@ func (h *Hub) run() {
 			if _, ok := h.clients[client]; ok {
 				delete(h.clients, client)
 				close(client.send)
+				log.WithField("client", client).Warn("delete client")
+				if len(h.clients) < 1 {
+					log.Warn("all clients left")
+					h.reader.Close()
+					h.running = false
+					delete(hubMap, h.getKey())
+					log.WithField("hub", h).Info("clear hub")
+				}
 			}
 		case message := <-h.broadcast:
 			for client := range h.clients {
@@ -268,7 +298,7 @@ func main() {
 
 	// hub := newHub()
 	// go hub.run()
-	r.HandleFunc("/ws/{topic}", func(w http.ResponseWriter, r *http.Request) {
+	r.HandleFunc("/ws/{topic}/{offset}", func(w http.ResponseWriter, r *http.Request) {
 		serveWs(w, r)
 	})